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By J. M. Roberts, N. Brown

The stress-strain behavior of zinc single crystals was measured over a strain range of 10-6 to 10-2. The phenomenon of macroyielding was observed in detail and plastic strains were detected at almost zero-stress. Closed hysteresis loops were observed during loading and unloading in the strain region of about 10-5. From the hysteresis a frictional stress on the dislocation of about 6 psi was obtained. A preliminary analysis indicates that impurities are primarily responsible for the friction. Nonelastic Strains as much as 10 -4 were recovered depending on the amount of prior deformation. Part of the recovered strain occurs instantaneously upon unloading and the remainder occurs at zero stress. The time dependence of the recovered strain was measured. THIS investigation is concerned with the details of plastic deformation preceding the ordinary yield point as measured with the usual strain sensitivity of about 10-4. The approach leads to internal friction observations in the hitherto neglected frequency range below 10-1 cycles per sec. It is believed that if the phenomenon of macroscopic yielding is to be understood, then the stress-strain curve in the neighborhood of the macroyield point should be greatly magnified. It may then be possible to determine whether macroscopic yielding is a unique event or whether it is a process which begins gradually at a lower stress. In the case of low-carbon steel a unique event obviously occurs at the macroscopic yield point as indicated by a drop in the load, but copper appears to exhibit a gradual transition from the elastic to the plastic state. In zinc the yield point is rather abrupt although the data indicates that some plastic deformation precedes large scale yielding.' One of the purposes of this investigation is to determine whether there is an abrupt transition from the preyield microstrain region to the region of macroscopic deformation. Such a rapid transition would support the concept that there is a critical stress for yielding. The concept that yielding is a unique event associated with such phenomenon as activating a Frank-Read source, freeing the dislocation from solute atoms, dislocations cutting through dislocations, or dislocations moving freely by one another, has been expounded widely on theoretical grounds. It is hoped that highly sensitive measurements of strain in the neighborhood of the macroscopic yield point will shed some light on the event known as the "Yield Point". EXPERIMENTAL METHOD 1) Specimens—High-purity zinc was cast into spherical graphite moulds in air and grown into spherical single crystals by the Bridgman method under a positive pressure of Argon gas. Spectro-graphic analysis of cleaved sections from four crystals showed a purity of 99.994 pet Zn. The specimens were acid machined with an 1/8 in. gage section in a form similar to those used by Parker and co-workers.2 Bausch type grips were fastened to the specimen by Epon VI adhesive. The specimens were oriented so that only [1120] (0001) slip occurred. Fig. 1 shows two of the specimens in the grips. Prior to each test, the gage section of the specimen was given a concentrated HNO3 chemical polish followed by alcohol rinsing and air blast drying. 2) Test Method- The shear tests were performed on an Instron testing machine and the experimental set-up was made very "hard". Strain could be measured to a sensitivity of 10 -6 by means of a capacitance gage extensometer. The design and calibration of this type of extensometer to measure microstrain, as applied to pure shear and tensile tests of metals, will be the subject of a separate paper—therefore, only a brief account will be presented here. The method essentially consists of attaching a

Jan 1, 1961

By L. H. Robinson

Triaxial compression tests on Indiana limestone indicate that chemical additives in the pore fluids can increase or decrease the strength in plastic failure but not in brittle failure. Tests using a series of the sodium salts of dicarboxylic acids show that odd-number carbon-atom chains decrease the yield strength as much as 3.0 x 10 3 psi, and even-number carbon-atom chains increase the yield strength as much as 9.0 x 102 psi. ,The most effective chemical (sodium citrate) decreased the yield strength of Indiana limestone from 16.0 x 103 to 12.0 x 103 psi. The chemical additives investigated have no influence on microbit drilling rate when drilling with zero differential pressure. However, when drilling at a 2.0 x 103-psi pressure differeniial and using an odd-number carbon chain compound as the circulating fluid, the roller bit drilling rates were slower than with water whereas the drag bit drilling rates were faster. One even-number carbon chain compound added to the circulating fluid produces the opposite effect: the roller bit drilling rate is slightly faster than with water and the drag bit slower than with water. INTRODUCTION A Russian book by Rehbinderl published in 1944 generated much interest in the possibility of aiding and accelerating the destruction of solids by the action of a liquid in which the solids are deformed. This book describes a process in which microcracks are generated during elastic deformation. To describe this process, the rock is divided into three zones: (1) the zone in which the destruction takes place, (2) the predestruc-tion zone (an affected area immediately below the destroyed zone) and (3) the undisturbed specimen. Consider a load applied normally to a surface of an infinite slab of rock. Immediately below the point of application of the load, the rock is destroyed by compression or shear forces. Below this area of destruction, because of a great number of discontinuities ranging from defects to weak points in crystals of discontinuities in crystal latices, very small cracks are created in or between the crystals (often referred to as microcracks). Upon removing the load, the broken rock in the destroyed zone could be removed. In the lower predestruction zone, however, the microcracks in and between the crystals could disappear by the process of rehealing, i.e., the molecular attraction from one side of the crack to the other side being sufficient to completely eliminate the crack. Thus, a large number of these microcracks possibly exist only for a relatively short period of time. The concept of small cracks being generated within the crystals of a rock is not unreasonable. If the rock matrix is deformed below the yield point, some of the defects present within the crystalline structure could start small cracks through the interior of the grains. Upon removal of the load, these microcracks reheal (or the newly generated surfaces come back together) so that all evidence of cracks completely disappears. Under various types of loading, and in various types of fluids, the rehealing of these cracks would be time dependent. If a liquid adhered to the surface of a rock, it could penetrate into the microcracks and thus delay or prevent the rehealing process. This suggests that the prevention of healing of the microcracks may be dependent upon the wetting characteristics of the solid. Thus, rocks which are water-wet should be more easily destroyed in water than in nonpolar hydrocarbon liquid. Adsorption of a liquid could also reduce the free surface energy which could explain the decrease in strengths of materials under nonrepetitive-type loading. Rehbinder's work prompted Boozer, Hiller and Serdengecti 2 to examine the effects of pore fluids on the deformation of rocks subjected to triaxial compression over a range of confining pressures, temperatures and strain rates. Fluids which strongly adsorbed on the rock grain surfaces decreased the strength of sandstone and limestone, which deformed plastically. For certain strain

By R. Grierson, R. N. Parkins

The m.echanica1 properties, at high lzomologous temperatures, of the intermetallic compounds InzBi and Mg17A112 were measured as a .function of temperature, applied strain rate, previous thermal and mechanical history, and composition. Mgl,Al12 was investigated ilz compression, whereas Zn,Bi was investigated in tension. A decrease inflow stress with increasing strain was observed jor both alloys. The results obtained are discussed in terms of the dislocation-multiplication processes in these materials. MANY intermetallic compounds are reported to undergo a brittle-ductile transition at high homologous temperatures.' There is evidence in the literature that some of these compounds exhibit a large yield drop when plastically deformed.'j3 Both of these forms of behavior are shown by the covalent elements germanium and silicon4,5 and also by certain ionic compounds.8 The present work is a study of the deformation, at high homologous temperatures (>2/3 Tm), of two intermetallic compounds, In2Bi and Mg17Al12. InzBi has a disordered hexagonal structure7 (c/a = 0.598) and a solubility range of 32.3 — 33.2 at. pct Bi.8 It has a melting range from 72° to 89°C. Mg17Al12 has an ordered bcc (A12 type)7 structure and exists over the range 50 to 60 at. pct Mg8 with a melting range from 437° to 462°C. We have been unable to find any reference to previous investigations of the mechanical properties of BiIn,. Novikovg has reported that cast samples of Mg17A112 show ductility, when bend-tested, at temperatures above 380°C. EXPERIMENTAL Ingots of In2Bi and Mg17Al12 were melted under an argon atmosphere and cast, in situ, in a graphite crucible. The materials used were of 99.99 pct purity. The alloys prepared contained 66.9 at. pct In in the case of In2Bi and 58.4 at. pct Mg in the case of m17A112. The ingots were homogenized and then extruded. Two-in.-diam Mg17Al12 ingots were extruded at 375°C to give 3/8-in.-diam rod. The rate of formation of this rod was 0.25 in. per min. One-in.-diam InzBi ingots were extruded at 20°C, using a rate of 1 in. per min, to give 1/8-in.-diam rod. In both cases the extruded rod had a recrystal- lized, fine-grain, structure. (For Mg17Al12, d = 11.2 µ; for BiIn2, d = 22 µ.) Mechanical-property determinations were made in a hard-beam machine, in tension in the case of In2Bi and in compression with Mgl7Al12. The tensile tests were on specimens having a gage length of 1.1/2 in. and a diameter of 1/8 in. The compression tests on Ml7A112 were on specimens of 3/8 in. diam by 3/8 in. high and the ends were coated with poly-tetrafluorethylene to minimize friction. RESULTS In2Bi. Fig. 1 shows, particularly at the higher applied strain rates, that In2Bi exhibits a marked yield drop as the deformation increases to about 2 pct, after which the material shows neither hardening nor softening up to 15 pct strain. The magnitude of the yield drop, the stress in the region of flow under constant stress (the stress plateau), and the 0.5 pct proof stress were all dependent upon the applied strain rate according to an expression of the form

Jan 1, 1965

By M. L. Hammond, G. M. Bowers

Silicon dioxide films have been prepared on silicon wafers by the oxidation of SiH, near 400°C. Results previously reported by Goldsmith and Kern7 have been qualitatively corrobovated using a system of different geometry, and significantly greater deposition rates have been achieved. The deposition rate is independent of thickness and nearly independent of the O2/SiH, ratio over a wide range; however, the rate is strongly temperature-dependent. The structure of the deposit depends upon the cleanliness of the substrate, and the electrical field strength of the deposited oxide depends upon the nature of the electrodes. MULTILEVEL interconnects in integrated circuits using aluminum metallization require an insulator that can be deposited at low temperature. Because the A1-Si eutectic is only 577°C, the maximum deposition temperature must be below about 500°C to prevent reaction of the aluminum with the silicon and with other materials in the integrated circuit. Many methods of depositing insulating films of SiO, and other dielectrics have been reported'-6 but the technique described by Goldsmith and Kern7 offers the simplest method of preparing SiO, films. The technique involves the reaction of SiH, and 0, to form SiO, films in the 300" to 500°C temperature range. Previous work using this gas system has been reported8 and the initial development work at Philco Microelectronics was done at the East Coast R&D Laboratories. 9 This paper corroborates some of the results of Goldsmith and Kern,7 shows that much higher deposition rates can be obtained than previously reported, and presents some observations on the structure of deposited SiO, films. EXPERIMENTAL CONDITIONS Fig. 1 is a schematic drawing of the apparatus used in this study. It differs from that of Goldsmith and Kern in that 1) the gases are mixed before they enter the reaction chamber, 2) there is no fritted glass diffuser, and 3) the wafers are stationary during deposition. The control thermocouple was in a well located 0.06-in. from the substrate, and three gas supplies were used: 1 pct SiH4 in N 2, O 2, and N 2. Water vapor must be excluded from the plumbing to prevent the formation of colloidal SiO, and the SiH4 must be diluted with an inert gas because SiH4-0, mixtures are extremely flammable above about 4 pct SiH The wafer temperature was determined by attaching a thermocouple to a test wafer and the temperature was maintained to +5 C. The conditions used in this investigation are listed in Table I. The temperature range was chosen for compatibility with the A1-Si system. The volume ratio of 0, to SiH4 is the actual volume of 0, delivered to that of SiH4, taking into account the initial dilution of the SiH4. This ratio, which was used by Goldsmith and Kern,7 is a useful indicator of the experimental conditions. The active/inactive ratio is the ratio of the volume of active gases, SiH4 and O2, delivered to the volume of dilution gas. The active/inactive ratio is an important parameter to specify for deposition rate determinations since it determines the amounts of reactants that arrive at the sample per unit time. Fairly high dilution ratios were necessary to achieve uniform deposits of SiO,. Most of the process characterizations were performed on the polished (111) face of 3 to 5 ohm-cm, n-type silicon wafers which were 0.009 in. thick; but the data approximately apply to deposition of SiO, on thin films of aluminum. It is difficult to obtain accurate deposition rate data over aluminum films because of coarsening the aluminum surface during exposure to 300" to 400°C. The deposited SiO, film fol-

Jan 1, 1969

By H. M. Manasevit, R. L. Nolder, L. A. Moudy

The observation that silicon-on-sapphire crystallo-graphic relationships exist which are unrelated to one another implies that there are regions of sapphire orientations containing these relationships which are separated by boundaries. The presence of these boundaries is demonstrated, initially on rounded cylindrical surfaces md more definitively on flat sapphire substrates with orientations along primary crystallograPhic zones. By means of reflection electron and X-ray diffraction techniques the crystallographic relationships have been studied. Two new relationships have been found, viz., (111) Si (1014) sapphire and (001)Si (1012) sapphire. Also found were multicrystalline relationships. The approximated boundaries between the crystallographic regions for each relationship are shown by means of a stereo-graphic projection. These studies also clarify discrepancies in the literature concerning the silicon-sapphire relationships on the (1120) sapphire substrate. SINCE the first report of the deposition of single-crystal silicon on sapphire in 1963' this epitaxial system has been the object of study by many semiconductor laboratories. In particular, there has been strong interest in the crystallographic relationships between the two materials. In 19652,3 we demonstrated that at least four distinct modes of orientation relationships can occur, namely, (100)Si (0112) sapphire, (111)Si 11 (1124) sapphire, (111)Si (1120) sapphire, and (111)Si (0001) sapphire. Each relationship could be obtained when the substrate plane was at the particular orientation indicated. Other workers as well as our laboratory concurred in general with the initial results. However, two discrepancies were observed. First it was observed by Joyce et a1.4 that on a (1120) substrate a (110) silicon deposit could be obtained. This was actually consistent with the (111)Si (1124) sapphire mode. Second, two other laboratories,5,6 as well as our own,7 have found a deposition on the basal plane which is different than our initial findings. Even though a (111)Si deposit was obtained, the crystallographic relationships were not identical to those previously found. Subsequent work in our laboratories has confirmed that the form found in these later investigations of the basal plane is by far the more predominant, and the original finding was an anomaly. The relationships which have been previously estab1.ished are summarized in Table I. It is seen that at present a rather small number of possible substrate orientations has been investigated. Therefore, it seemed appropriate that a systematic investigation of silicon epitaxy on various sapphire substrate orientations would be of value. It was expected that the answers to three questions could be obtained from such an investigation. These are as follows: 1) Since we know of at least four distinct modes of orientation relationships, over what range of substrate orientation do these modes occur and what is the form of the boundary expected between the different regions in which each mode occurs? 2) Are there other modes which occur on substrate orientations not previously investigated? 3) What is the explanation for the discrepancy between our laboratory's findings and those results reported by Joyce et al.4 concerning the relationships occurring on (1120) substrates? APPROACHES AND EXPERIMENTAL METHODS Two different approaches were used. Initially, depositions were carried out on rounded cylindrical surfaces which lay perpendicular to the (0112) plane.* By this means the presence of boundaries and their approximate positions could be determined. Finally and more definitively, depositions on flat sapphire substrates with a variety of orientations, mostly along primary crystallographic zones and about the (1120) plane, were studied by means of reflection electron diffraction and X-ray diffraction (using back-reflection Laue patterns and full circle goniometer techniques) in order to determine crystallographic relationships. The sapphire orientations investigated by these means

Jan 1, 1969

By R. W. Heckel, H. W. Paxton

The growth of grain boundary films and Widmanstiitten plates of proeutectoid cementite in hypereutectoid steels ulas considered quantitatively in three plain carbon steels and one "pure" iron-carbon alloy. Growth was found to take place at a slower rate than would be predicted on the basis of a model invoking rate control by long range diffusion of carbon. The films in the pure alloy grew faster than those in the plain carbon steels. A possible explanation is suggested. In 1904, Nernsst' and Brunner2 postulated that ionic crystals growing in supersaturated aqueous solutions grew at rates determined by diffusion through the solution to the growing crystal interface. The gradient down which the diffusion took place was assumed to be fixed by the supersaturated bulk solution concentration, the concentration dt the crystal surface and some arbitrary distance. The flux of material to the crystal was described as Flux where D is the diffusion coefficient, A the crystal surface area, Ci the bulk solution concentration, Co the saturated solution concentration, and 6 the thickness of the diffusion zone. It is obvious that the expression is an adaptation of F+ick's3 first law of diffusion (steady state). This was the initial formulation of what will be defined here as "diffusion controlled growth," i.e., growth limited by the long range diffusion of a component either to or from the advancing interface assuming both phases at the interface to be in equilibrium. This idea of equilibrium interface concentration implies an infinite reaction rate at the interface. Volmer, Zener,' and 11schner6 have derived expressions for the diffusion controlled growth of spherical precipitates in metallic systems. These analyses agree that the growth in a given direction should be parabolic with time. Brown and Hawkes7 observed that graphite, formed both from the decomposition of cementite and from the decomposition of eutectoid austenite in cast irons, grew according to a parabolic relationship and, therefore, concluded that the laws of diffusion controlled growth, as defined above, were obeyed. They, among others, failed to consider, however, that parabolic growth is a necessary, but not sufficient, condition for diffusion controlled growth. Mehl and Dube"' have pointed out that equilibrium may not be realized because the concentration at the interface cannot change instantaneously from that of the bulk to the saturation value. Furthermore, they propose that an equilibrium solute concentration in the parent phase adjacent to the precipitate would remove the thermodynamic activity gradient across the interface and, thus, stop the growth process. Frisch" has also emphasized the importance of interface concentrations that vary throughout the growth of a new phase. The variation in activity across an interface, as discussed by Onol' and Cahn and Hilliard,12 is of fundamental importance to this question. Ham13 considered the data of Turnbull14 on the growth of barium sulfate in aqueous solutions. He concluded that the data could be analyzed in terms of a radiation-type boundary condition. Flux across interface = K (c, - C,) [21 where C, is the concentration in the solution at the interface, Co the saturated solution concentration, and K the proportionality constant. The edgewise growth of Widmanstlitten plates, frequently referred to as the rate of lengthening, was first considered by Zener.'' Basing a mathematical analysis on steady-state (constant velocity) growth he concluded that where G is the growth rate, D the solute diffusivity, Ci the concentration in the bulk, Co the equilibrium interface concentration, C, the concentration in the precipitate, a a constant, Y the radius of curvature of the edge of the plate, and rC the critical radius, i.e., the radius which would increase the activity of solute at the interface at equilibrium under the influence of capillarity to that of the bulk. Zener1'

Jan 1, 1961

By W. G. Pfann

Under certain conditions, a molten zone can be made to move through a solid by impressing a stationary temperature gradient across the solid. This phenomenon can be utilized in fabricating semiconductive devices, growing single crystals, joining, boring fine holes in solids, measuring diffusivities in liquids, small scale alloying, and purification. Fundamentals and exemplary applications are outlined. ANEW aspect of the travel of a molten zone through a solid is considered in this paper. Whereas, in previously described zone melting techniques,'-' zones were usually caused to move by changing the position or temperature of a heat source, in the present technique a zone is made to move by impressing a temperature gradient across it. For example, a thin layer of molten A1-Si alloy, sandwiched between two silicon slabs having a temperature gradient normal to the layer, will travel through the hotter slab. One feature of temperature gradient zone melting, as this technique will be called here, is that zones of unusually small dimensions can be maintained. This leads to such diverse uses as have been listed in the abstract. In this paper fundamentals of the movement of a molten zone in a temperature gradient, and some practical applications thereof, are outlined. Assumptions The movement of a molten zone through a solid body of solvent substance in which a temperature gradient exists will be discussed. The length of the zone will be its dimension in the direction of motion. The direction of the temperature gradient will be toward the region of higher temperature. To be considered is a binary or higher order solute-solvent system in which the concentration of solute in the molten zone is sufficient to produce a lowering of the freezing temperature of the solvent which is at least of the order of the temperature range impressed on the charge. While we discuss primarily molten zones in a solid matrix, the principles are applicable to solid or vaporous zones in a solid matrix, a requirement being that the diffusivity in the zone be substantially greater than in the matrix. Diffusion of solute into the surrounding solid will be assumed negligible. In general, its presence will not basically alter the conclusions to be drawn. For illustration, a system represented by the partial constitutional diagram of Fig. la will be discussed, in which k, the distribution coefficient defined in the figure, is constant and less than unity. However, the technique is applicable to any solute- solvent system in which one component lowers the melting point of another component. Movement of a Molten Zone in a Temperature Gradient Consider, in the system AB of Fig. 1, where B is designated the solute and A the solvent, the effect of sandwiching a thin layer of solid B between blocks of solid A and placing the whole in a temperature gradient such that the temperature of the layer is above the lowest melting temperature of the system. Surrounded by an excess of A, the layer will dissolve A, becoming molten, and expand in length." As so- lution of A continues, at both interfaces, the mean solute concentration in the zone will move to the right in Fig. la, until at temperature T, the liquid at the cooler interface reaches the liquidus concentration C,. Solution of A thereupon ceases because the liquid T1 is saturated with A. The liquid at the hotter end of the zone, being at temperature T2, is not saturated with A at concentration C1. Hence solution of A continues there and concentration C2 is approached. A concentration gradient therefore is set up in the zone, causing A to diffuse toward the cool end and B toward the hot end. As a result, the liquid at the cool interface becomes supersaturated and a layer of crystalline A containing concentration kc, of B in solid solution freezes. Since a source of A

Jan 1, 1956

By C. Chu

A theoretical investigation has been made of the forward combustion process using a one-dimensional linear mathematical model, taking into consideration the effect of the vaporization-condensation which occurs on the leading edge of the heat wave. This work involves the solution of five coupled partial differential equations. Besides the vaporization-condensation phenomenon, these equations account for conduction, convection, combustion, heat loss, diffusion and bulk fluid flow. For the one-dimensional linear model studied, the vaporization-condensation phenomenon does not induce appreciable change in the temperature at the combustion front; and its primary effect is to create a steam plateau and to increase the length of the heated zone ahead of the combustion front. This effect becomes more pronounced at lower pressures, higher porosities or reduced gas saturations. The peak temperature and the temperature profile on the leading edge of the heat wave stabilize after a certain period. The length of the steam bank remains practically constant, although the length of the water bank increases as the heat wave advances. INTRODUCTION The existence of the vaporization-condensation phenomenon in the heat-wave process and the important role played by the phenomenon have been recognized by several investigators. Kuhn and Kochl stated that steam plateaus were frequently observed on the temperature records of their experiments. The steam plateaus were attributed primarily to the vaporization and subsequent condensation of the interstitial water existing in the oil sand. Szasz2 suggested that both lighter hydrocarbons and water are vaporized on the leading edge of the heat wave, carried forward in the gas stream, and then condensed to create banks of oil and water. Martin et al suggested that the vaporization-condensation phenomenon is one of the main mechanisms of the heat-wave process, along with thermal expansion and viscosity reduction. Wilson et al. reported the existence of a steam plateau several inches in length in their small-scale tube-run experiments. However, this important phenomenon has never been taken into consideration in the numerous theoretical analyses by various authors. 5 The purpose of this work was to study the thermal aspects of a linear heat wave, taking into consideration the vaporization-condensation on the leading edge of the wave, to determine the effect of this phenomenon on the temperature profile of the reservoir, and to investigate how this effect varies when other process variables are changed. THEORY We consider a reservoir of porous medium of cross-sectional area A, extending from x = 0 to x = L. This reservoir contains, aside from the solid matrix itself, a gas phase and a "combined liquid phase" which is a combination of two immiscible liquid phases — namely, an oil phase and a water phase. The oil present in the reservoir is assumed to consist of three fractions, a noncondensable gas, a nondistillable residuum, and a vaporizable oil fraction which may be present in both the gas phase and liquid phase. Before the heat-wave process begins, preheating has taken place and has imparted an initial temperature distribution T,(x) to the reservoir. At the start of the process, a stream of oxygen-bearing gas is introduced through the face at x = 0. This gas supports the combustion of the residual fuel and supplies the heat throughout the process. In order to develop a tractable system of equations, the model properties are postulated as follows: (1) the system is isotropic and homogeneous; (2) there is a uniform fuel content throughout the reservoir; (3) combustion takes place in a moving vertical planar region of infinitesimal thickness; (4) the temperatures of the fluids and the solid matrix are identical; (5) radiation is negligible; (6) the gas and liquid saturations are uniform throughout the reservoir and remain unchanged

Jan 1, 1965

By M. Cross

INTRODUCTION The development of refining processes involving gas injection into liquid metals has seen the evolution of a variety of designs [I]. During the last few years or so the top, bottom and side blown processes have, essentially, been combined to produce a series of mixed gas blowing schemes (eg. the LBE [2,3] and LD-OB processes [4,5]). Although, a variety of mixed gas blowing processes have been carefully engineered and recorded operational experience now attests to their effectiveness, optimising their design and operational performance is another matter. Detailed process analysis of such operations is impeded by the complex nature of the physical and chemical processes involved: . fluid flow behaviour of the liquid metal and injected gases, . chemical reactions in the vessel, . mass and heat transfer within the fluid phases in the vessel, . influence of the geometry (eg. location of the tuyeres, etc.), . monitoring the operational performance. By and large, design and operating parameters evolve from a combination of laboratory scale experiments, pilot plant work and, of course, practical engineering experience. Conventionally, the gas-liquid system used to model the industrial process is air-water, for a number of valid reasons including – . visual demonstration plus geometric and (to some extent) dynamic similarity, . the fact that the system demonstrates, at least, qualitatively many of the complex features of gas injection - interaction between the gas and the liquid - the nature of the gas flow behaviour - qualitative indications of mass transfer rates Important experimental contributions to the understanding of gas liquid systems include the work of Brimacombe [6], Wraith [7], T.Robertson [8], D.Robertson [9], Guthrie [10] and Szekely [11] (these references provide starting points to identify the major published work in this area). Although air-water systems have been instrumental in providing a great deal of qualitative insight into the fluid flow behaviour of the processes, reliable quantitative predictions are more problematic. A number of workers (notably Brimacombe and colleagues [6, 12])have demonstrated that different gas-liquid systems can lead to wide variations in behaviour. Other limitations of physical modelling include the assumptions of isothermal flow, scale- up of turbulent flow behaviour and the inability to directly include the effects of chemical reactions. The above limitations in physical modelling, therefore, yield a natural role for mathematical modelling provided that it can be made comprehensive enough whilst remaining cost-effective. The major physical processes involved in gas injection systems may be summarised as . behaviour of the gas envelope structure in moving through the liquid metal . the global movement of the liquid metal . momentum interaction between the liquid metal and the injected gas . heat transfer and mass exchange via the chemical react ions. The behaviour of gas envelopes forming at a tuyere and then moving through the liquid has been investigated thoroughly by a large number of workers. Such models are generally based upon simple physic- al concepts derived from visual observation. An early model by Davidson and Schuler (DS), based upon a force balance between the liquid inertia and a combination of the bouyancy and momentum forces on the envelope, has proved to be a useful tool in predicting bubble volumes at detachment [13]. The DS model has been successfully modified in a number of ways [14-17] to cope with heat transfer and reactive transfer rates, etc. Furthermore, the basic ideas summarised above have also been confirmed on industrial converters by both Guthrie [I8] and Brimacombe [19]. Models have also been developed to predict the behaviour of the "chemical" component of some gas-liquid systems. However, one thing is clear; all gas-liquid reactive systems are governed by the degree to which effective mixing occurs. As such, the processes are dominated by the behaviour of the heat and mass exchange of the two phase fluid flow system. It is the pattern of movement of the turbulent liquid metal plus its interaction with the injected gas which must be predicted reliably, if sufficiently comprehensive comp-

Jan 1, 1984

By I. Zaplatynskyj, G. C. Kuczynski

SINCE the excellent studies of metal powder compaction executed by Kamm, Steinberg, and Wulff, no work on the subject has appeared in the technical literature. Kamm et al. were the first to investigate quantitatively the distribution of density in a powder compact, as a function of pressure, height and diameter of the die, powder particle size, etc. For this purpose they devised a very ingenious method. They inserted a thin lead grid into a die and then filled the die with powder. During cold pressing, the lead grid -moved downward. Due to its deformability it followed closely the downward descent of the adjacent powder. The die was then radiographed and, from the deformations of the grid openings measured on the radiographs, the density in the vicinity of each opening was evaluated. Their findings led them to the conclusion that the friction on the side walls of the die is a major controlling factor of the density distribution inside the cold pressed powder compacts. However, it is difficult to conduct tests similar to those of Kamm, Steinberg, and Wulff in a processing plant laboratory, which usually lacks the necessary expensive radiographic equipment. The purpose of this note is to describe a method which makes it possible to determine the density distribution in green powder compacts with the same accuracy as the lead-grid method but which is far simpler and faster and requires only standard laboratory equipment. Instead of using a lead grid, the hardness at selected points of the sectioned compact is determined. If the relationship between hardness and density is known the density distribution is readily obtained. This relationship is easily found from measuring hardness and densities of thin compacts. In such compacts the density, for all practical purposes, is constant throughout. The method was tested on a Plast nickel powder, grade FlA-A20, kindly supplied by Plast Metals Co. Thin compacts (height to diameter ratio 0.2) were pressed in a single action cylindrica1 die at various pressures. The density of the compacts was determined by weighing and by measuring the height and diameter with a micrometer. Subsequently the Rh hardness was determined. Up to ten readings were taken on each specimen. The difference in hardness readings on each compact was never greater than three corresponding to about 0.1 g per cu cm uncertainty in density. By varying the compaction pressure of the samples, a whole scale of densities was obtained allowing construction of a set of density-hardness calibration curves. To test the method several compacts of different height were pressed under varying pressures. Die walls were always well lubricated. After pressing, the compacts were mounted in bakelite and halved by grinding, and hardness readings taken along the diameters of the specimens. The distance between adjacent indentations was about 2.5 mm. After hardness readings were translated into densities, contour maps of densities of the compacts were prepared. One of them is reproduced in Fig. 1. The areas encompassed by the curves are labeled with numbers representing the density in g per cu cm of those regions. In Fig. 2 the same results are re-plotted to emphasize the radial density changes at various depths. The results thus obtained confirm the findings of Kamm, Steinberg, and Wulff kentioned previously. They are recapitulated here briefly. 1—The densest part of a compact pressed from one side is at the outer circumference at the top and the least dense part at the bottom, at the outer circumference. Figs. 1 and 2 show this clearly. 2—The density near the cylindrical surfaces of the compact decreases uniformly with height from top to bottom. 3—The density variation increases with the height to diameter ratio. References R. Kamm, M. A. Steinberg, and J. Wulff: Trans. AIME (1941) 171,'R. p. 439 ;MetaLs Technology (February 1941). R.p. Kamm, M. A. Steinberg, and J. Wulff: Trans. AlME (1949) 180, 2R.P. 694; MetalS Technology (December 1948).

Jan 1, 1957

By Oren C. Baptist, Eliot J. White

Samples of four reservoir sands having different degrees of water sensitivity were subjected to several laboratory tests to determine differences in capillary behavior attributable to clay-mineral effects. The degree of water sensitivity was estimated by the difference between gas and water permeability. Unsaturated pore volumes determined with mercury injection were comparable to irreducible water saturations determined with the semipermeable bar-rier method only for the non-sensitive sands that contained small amounts of non-swelling clay minerals. Irreducible saturations were independent of salinity of the water, which suggests that most residual water is adsorbed 0.7 a film over solid surfaces and that internal retention by clay minerals is relatively insignificant. The water-sensitive sands imbibed water to higher saturations than did non-sensitive sands, and this result is believed to be a combination of the effects of clay minerals and preferential wettability; however, the relative importance of each of these effects is riot determinable. Thus it is concluded that the semipermeable barrier method is the best of the laborafory methods used for estimating formntion water .saturations in the sands studied. INTRODUCTION This investigation is a continuation of studies of the role of clay minerals in petroleum production in the Rocky Mountain area. Previous work has shown large differences in gas and water permeability in numerous reservoir sands; these water-sensitivity effects observed in the laboratory have been correlated with well behavior in the field, and the degree of water sensitivity imparted to reservoirs by the various clay minerals has been determined.'.' The effect of interstitial clay minerals on formation water3 saturations is not so well known. It has been reported that formation water saturations probably are higher in clayey than clean sands,' but this effect has not been evaluated in the laboratory, and the relative effect of the various types of clay minerals on formation water saturation has not been determined. The clay-mineral groups of most importance to this study and to petroleum production in general are kaolinite, illite, and montmorillonite. The minute layers of montmorillonite are loosely bound to one another so that water enters between them, causing great expansion of the particles. Kaolinite and illite do not exhibit interlayer hydration, but they do immobilize considerable amounts of water owing to their large surface areas, which are of the order of 15 to 97 m2/gm of clay.5 The four Wyoming sands used in this study were selected to represent a wide range of water sensitivities. These sands, with the number of wells and fields from which the samples were obtained, are: Second Frontier, five wells in two fields; Newcastle, six wells in one field; Tensleep, two wells in two fields; and Lower Muddy, five wells in one field. EXPERIMENTAL METHODS AND PROCEDURES Water-displacement data were obtained by the semipermeable barrier method," using both fresh water and brines having either 16,500 ppm sodium chloride or calcium chloride. A displacement pressure of 35 psi was found to be sufficient to obtain the practical irreducible water or brine saturation (IWS, IBS) in most samples. Mercury-injection data were ob-tained with equipment and pro-cedures similar to those described by Purcell.7 Exceedingly high pressures are required to attain complete mercury saturation by this method; however, since saturations in most samples change very little with large pressure increases above 1,000 psia, the maximum pressure used was 1,400 psia. To facilitate comparison of mercury-injection and water-displacement results, it is convenient to express mercury-injection data in terms of unsaturated pore volume. The abbreviation, (100 - SHg)min, is used to denote the pore volume unsaturated by mercury at 1,400 psia injection pressure. Gas permeabilities, ki, were deter-mined by the method proposed by Klinkenberg.8 Methods of determining types and amounts of clay minerals by X-ray diffraction analyses, as well as methods of determining water permeability, have been described previously.' The imbibition characteristics of

Jan 1, 1958

By W. B. Mather

Of the 61 dikes examined some yielded cassiterite, tantalite, and beryl; eight contained spodumene; and six carried amblygonite. Two mines stockpiled spodumene as a byproduct. Only zoned pegmatite dikes carried lithium minerals. GEOLOGICAL studies have revealed the occurrence of hundreds of pegmatite dikes in northeast Brazil, Fig. I, in the three states of Rio Grande do Norte, Paraiba, and Ceara. Heretofore data have not been available on the possible production of lithium minerals from these areas, and in March, April, and May 1953 the author undertook a reconnaissance survey covering a cross-section of the pegmatite~. Sixty-one pegmatites were examined. The pegmatites of Rio Grande do Norte and Paraiba are located in an arid region (Seratao), and except in the most southerly portion there is a minimum of vegetation and overburden. The region is easily prospected and relatively accessible by jeep or truck. The pegmatites examined in Ceara are in an area of lush vegetation along the flanks of the Jaqueribe River valley. It is therefore more difficult to prospect, and the dirt roads, as a means of access, leave much to be desired. For all practical purposes rail transportation, except in Ceara, is not available. The rocks of the area are composed of Pre-Cambrian schist, gneiss, quartzite, and marbles. They have been intruded by granites, monzonites, and diorites and cut by quartz veins and pegmatites. Pre-Cretaceous erosion reduced the area to a peneplain upon which Cretaceous or younger sandstones were deposited. Recent erosion has left only a few remnants of these younger rocks. In most of the Rio Grande do Norte-Paraiba area the pegmatites were more resistant to erosion than the enclosing schists and therefore stand out in relief. This is not true in the rolling country of Ceara, where the pegmatites lack topographic expression. With regard to structure and lithology, the pegmatite~ of northeast Brazil are divided into two types, uniform and zoned. Of the 61 examined, 19 belong to the uniform and 42 to the zoned type. Uniform pegmatites are normally long, narrow, and tabular, with sharp contacts. They are composed of an intimate mixture of feldspar (microcline or ortho-clase), mica (biotite, phlogopite, or muscovite), and quartz. The grain size5 varies from fine at the contact to coarser in the interior. They are not considered a commercial source of pegmatite minerals, although efforts have been made to produce green beryl of gem variety. This type of dike is often abundant in schists and gneisses close to granite intrusives. The productive dikes — lenticular, pod-shaped, or irregular in outline, with sharp contacts — are of the zoned variety. Zone contacts are gradational, except for those with the quartz core. Zones re identified as follows, see also Fig. 3. Border Zone: This outer zone, in contact with the country rock, is composed chiefly of fine-grained muscovite and biotite, with lesser quantities of finegrained microline and quartz. It is the narrowest zone, usually measurable in inches. Wall Zone: Lying between the border and intermediate zones, the wall zone is composed of medium-grained feldspar (often microcline), muscovite, and quartz. Usually it is the widest zone. Widths of 50 ft were noted. Intermediate Zone: Lying between the wall zone and core, the intermediate zone is composed principally of coarse-grained microcline (occasionally with some orthoclase and albite). It may also carry minor amounts of coarse-grained quartz and fine to medium-grained mica. The width varies from less than 3 ft to more than 30 ft. Core: The center of the dike is composed almost entirely of massive quartz, occasionally with minor amounts of fine-grained muscovite. The width reaches 30 ft. Lithium and other minerals of potential economic value are found in the following zones:

Jan 1, 1955

By L. A. Wood, A. G. Winslow

Subsidence has occurred in several areas of the upper Gulf Coast region of Texas, although in most cases this is not evident without precise instrumental leveling. As referred to in this report, the region comprises about 7200 sq miles of the Gulf Coastal Plain and includes all or parts of the following counties: Harris, Fort Bend, Waller, Brazoria, Galveston, Liberty, Chambers, Orange, and Jefferson (Fig. 1). Topographic relief is low, ranging from sea level at the Gulf of Mexico to 300 ft or more in northwestern Harris County. In this upper Gulf Coast region, which embraces the most heavily populated and industrialized parts of Texas, industrial and municipal water supply is obtained chiefly from wells. Largest center of ground-water withdrawal is the Houston-Baytown area, where about 200 million gallons per day was pumped in 1956 for municipal and industrial use. Other large centers of ground-water withdrawal include the Alta Loma sector and the heavily industrialized Texas City area in Galveston County, where about 23 mgd was pumped in 1956. In the Freeport area in Brazoria County about 6 mgd was pumped in 1956 for city and industrial supply. In addition to withdrawals in metropolitan districts, great quantities of ground water are supplied by irrigation wells to thousands of acres of rice. These wells are widely dispersed over many miles, principally in Harris, Waller, Fort Bend, Brazoria, and Liberty counties, and effects of pumping are not so readily noticed as in the industrial and metropolitan sectors. Subsidence: Starting with the 1905-1906 line from Smithville, Tex., to Galveston, the U. S. Coast and Geodetic Survey has extended a network of first and second-order level lines throughout the upper Gulf Coast region. In 1918, when a line was run from Sinton, Tex., to New Orleans, La., a tie was made to the 1905 leveling at Houston. In 1932-1933 a line was run from Palestine, Tex., to Houston, and a good deal of leveling was carried out in the vicinity of Houston. At this time the entire network was adjusted to the Sea Level Datum of 1929. In 1935-1936 and 1942-1943 several new lines were run and considerable releveling was performed. Supplementary adjustments were made after both the 1936 and 1943 levelings in order to reduce the elevations to the Sea Level Datum of 1929. These adjustments probably masked some of the subsidence that had occurred up to that time, although a certain amount of subsidence was noticed in the 1943 leveling. When several lines in the vicinity of Houston and Galveston were releveled in 1951, the regional nature of the subsidence became apparent.' Direct comparison with the 1943 leveling was possible because the datum was not changed. Comparisons with prior leveling were unreliable because of differences in the early and subsequent datums. In 1953-1954 many lines in the region were re-leveled and in 1957 the entire network, including the elevations previously determined, was readjusted to determine the changes in elevations as indicated by various levelings between 1905 and 1953-1954. In this instance the adjusted elevations were held fixed near the boundaries of the region where the bench marks seem to have remained stable. The only sea-level connection held fixed was the connection of the 1905 leveling to the 1903-1906 tidal series at Galveston. Almost the entire region has been at least slightly affected by the subsidence, some areas to a great extent. The profiles of subsidence (Fig. 2) and the map showing the contours (Fig. 3) illustrate both regional and local changes. A large area of subsidence is centered in the Houston-Baytown district, where the maximum recorded is about 2.7 ft between 1905 and 1954. This probably falls short of the actual maximum, since land surface subsided as much as 2.5 ft in the industrial section alone between 1943 and 1954. Sub-

Jan 1, 1960

By S. R. B. Cooke, H. S. Choi, D. H. Harraway, I. Iwasaki

The mineralogy of natural iron ore samples and their slimes have been investigated and the nature of slime interference in iron ore flotation has been studied. The results have been correlated with the flotation behavior of a natural ore sample. Various conclusions have been reached as a result of these studies. In the flotation of iron oxide ores, desliming is generally considered to be an essential step to successful separation, irrespective of whether the iron oxide or siliceous gangue minerals are to be floated, although some workers have found empirically that certain collectors and reagent combinations are less sensitive to the presence of slime than others. The detrimental effect of slime is considered to be twofold. First, the presence of slime presupposes a high reagent consumption because of high specific surface. When clays are present and when cationic collectors are used abstraction by ionic exchange may augment this condition. Attempts to compensate by the addition of large amounts of reagent result in only partial correction. Second, slime coatings on granular particles tend to interfere with the bubble-mineral contact. The nature of slime coatings in flotation is quite complex and has been the subject of considerable study; an attempt was recently made by Fuerstenau et al.' to relate the slime-coating density with flotation recovery and with the properties of the electrical double layer at the mineral surfaces. Although major constituent minerals in the oxidized iron ores of the Mesabi and Cuyuna ranges are hematite and goethite (limonite) as the iron oxides, and quartz and chert as the siliceous gangue, very little is known of the mineralogy and of the chemical and physical characteristics of the slimes, and still less of the interaction between slimes, collector, and the mineral surfaces. For pragmatic reasons iron ore slimes are defined as — 20p material, based upon the calculated settling velocity of a quartz sphere of the stated diameter, and of all other equal-settling mineral particles. Active slime interference with flotation is usually attributed to particles 5p in size or finer, the extent of such interference appearing to depend not only on the mineralogy but also on the size distribution of each mineral in the slime fraction. The objective of this work was to acquire a more specific knowledge of the constitution of iron ore slimes and of their role in flotation. The mineralogi-cal composition of natural slimes was obtained by differential thernal analysis (hereinafter referred to as DTA), electron microscopy, and chemical and X-ray analyses. Some flotation tests were made on natural ore samples. The surface properties of several constituent minerals were investigated by electrophoretic measurements and by determination of the adsorption of some typical flotation collectors. Finally, simplified flotation tests were made on granular goethite and quartz in the presence of various artifically prepared slimes; the results were compared with laboratory flotation tests made on natural ores. MATERIAL AND METHODS Mineralogy of Some Iron Ore Slimes: Samples of two wash-ore tailing::, hereinafter identified as A* and B, *Sample A of the present investigation 18 the same am ore A in ref. 3. of a wash ore C, and of a paint rock D, all from the Mesabi range, were selected for investigation on the basis of prior information concerning their flotation behavior. The two wash-ore tailings, when deslimed, were known to respond well to flotation, whereas the wash ore was high in goethite, tended to be slimy, and responded poorly to flotation. The paint rock also exhibited sliming tendencies, and was suspected to contain relatively large quantities of clay minerals because of its high A1203 content. Gruner states that the paint rock of the Mesabi frequently contains kaolinite. To ascertain the relative sliming tendencies of each sample a standardized desliming method was employed. All samples were ground through 65 mesh using jaw and rolls crushers. A 500-g sample of each

Jan 1, 1962

By Nigel B. Pearson

INTRODUCTION Chingola Division of Nchanga Consolidated Copper Mines Limited is situated in the Copper- belt of Zambia, approximately 30 kilometres south of the border with Zaire. It is the country's leading producer of copper and its principal foreign exchange earner, and has been, in its time, the largest single copper producer in the British Commonwealth and the second largest in the world. There are two 'primary' copper sources at the Division, namely Underground producing approximately 100 000 tonnes of contained copper annually, and the Open Pits, producing approximately 200 000 tonnes annually. Following the commissioning of the Tailings Leach Plant in 1974, treating final tailings, metallurgical recovery increased from approximately 70% to in excess of 80%. Extensive deposits of cobalt are present and following the rise in the market price in 1979 and 1980, plans were made to extract this separately. Cobalt production commenced in 1980 from Underground and will increase substantially when the Open Pit cobalt reserves become available in approximately 2 years time. This paper covers the development of the production method of the principal Underground Orebody, known as the Lower Orebody, and the control systems applied to it. HISTORY The Lower Orebody, formerly known as the Nchanga West Orebody, was discovered by extensive Diamond Drilling operations in the late 1920's. Development of the Shaft complex and the orebody commenced and continued until 1931 when flooding from development on the 480 foot horizon necessitated closure. The mine remained closed until 1937 and production commenced from the Lower Orebody in 1939. Various expansion schemes of the Metallurgical Plants and the Underground workings were completed over the years with the result that Underground production increased steadily to in excess of 150 000 tonnes copper annually in the 1960's. In recent years production has levelled out at slightly less than 100 000 tonnes annually. This decrease is as a result of producing from a lower grade reserve, available within a more limited production front, and the application of production constraints in the light of experience gained. GEOLOGY Within the Nchanga Mining Licence Area of Chingola Division, there are a total of 14 known copper orebodies in the basal part of a thick succession of sediments of Pre-Cambrian age. The sediments rest on a Basement Complex of granites, gneisses and schists. Three superimposed stratiform orebodies, known locally as the Lower, Intermediate and Upper Orebodies, occur over a vertical interval of approximately 150m. Current annual copper production is approximately 300 000 tonnes. The ore originates from four different mining operations, one Underground mine and three Open Pits. Approximately 9 million tonnes of ore grading between 3 and 3.5% copper are milled annually. The two largest sources of ore, the Under- ground mine and the Nchanga Open Pit are on the gently dipping south limb of the Nchanga Syncline (Figure 1). In the Nchanga Open Pit the major source of ore is the Upper Orebody with lesser tonnages from the Intermediate and Lower Orebodies. In the Underground mine the Lower Orebody is the only orebody being mined, underground mining of the Upper Orebody being suspended for economic reasons in 1978. The typical stratigraphic column is illust- rated in the legend on Figure 1. The footwall rocks comprise either Nchanga Red Granite or the Arkose formation, both of which are hard competent rocks, offering generally good mining conditions for footwall development. Copper mineralisation of the Lower Orebody extends from the upper part of the Arkose to the top of the Lower Banded Shales. Overlying the Arkose is the Transition zone (0-18111 in thickness). The Transition zone comprise a lower member, Transitional Arkose, consisting of incoherent kaolinised sandstone, and an upper member, Transitional Lower Banded Shales consisting of normally soft bleached and silicified shale. The soft nature of the Transitional rocks is

Jan 1, 1981

By M. N. Pathasarathi, P. A. Beck, T. J. Koppenaal

EARLIER work1 indicated that in rolled and annealed copper the volume fraction of the cube-texture component may increase on continued isothermal annealing. Merlini found2 that in rolled copper the well-known increase in the amount of cube-oriented material with increasing annealing temperature3 is concurrent with grain growth, which takes place after recrystallization is complete. It was found that both in copper2 and in aluminum4 the texture resulting from primary recrystallization, even if this is followed by some grain growth, may in general comprise, in addition to the cube-texture component, four symmetrical texture components of the general type (123)[412], i.e., components not very far from the ideal orientations of the rolling texture. The volume fraction of the cube-texture component increases on further annealing at the expense of these four components.' The present work was undertaken to study quantitatively the increase in the volume fraction of the cube-texture component in the course of normal grain growth, under varying conditions. Since the grain-gr3wth behavior of A1-Mn alloys has been already investigated in some detaiL5 an A1 + 0.8 pct Mn alloy was chosen for this work, in which the extent of normal grain growth can be effectively controlled by the inhibiting effect of a dispersed second phase. EXPERIMENTAL PROCEDURE High-purity aluminum of the following composition was used: A1 99.997 pct, Cu 0.0004 pct, Fe 0.0005 pct, and Si 0.001 pct. A high-purity A1-Mn master alloy was prepared by dehydrating manganese chloride at 500°C and reacting it with molten high-purity aluminum at 750°C in a graphite crucible.5 The Mn metal reduced from the salt by the molten aluminum goes into solution in the latter. The master alloy? containing 13 pct Mn, was solidified under conditions suitable for minimizing segregation. An ingot of the final alloy, to be used in the experiments, was per pared by melting high-purity aluminum and the necessary amount of master alloy in a graphite crucible, and by pouring the molten alloy into a graphite mold preheated to 700°C through a box containing graphite baffles designed to intercept most of the aluminum oxide films floating in the melt. The melt was then solidified by placing the mold on a water-cooled copper plate and by keeping the top of the mold hot, in order to minimize piping. The 6 1/2 in. long, 11/4-in.diam ingot consisted largely of a single crystal. Chemical analysis showed that there was little segregation from the bottom (0.83 pct Mn) to the top (0.81 pct Mn). Spectrographic analysis of the ingot showed that the impurity content remained essentially the same as that of the aluminum used. The ingot was processed so as to obtain a uniformly small grain size. without banding. The ini-tial steps of rolling in the form of a flat bar and of annealing, down through a thickness of 0.4 in., are shown in Table I. At this point the bar was cut into four sections, each approximately 3 in. long, which were processed separately as shown in Table If. The table also gives the penultimate grain sizes obtained in each section by annealing prior to the final rolling of 90 pct RA. During the final rolling the strips were reversed end to end between passes. Annealing treatments were given in a salt pot furnace, with the temperature controlled to 1°C. All annealing of section "6s" was carried out above the solvus point to avoid the formation of second-phase precipitate. The penultimate annealing was sufficiently short to give a relatively fine grain size in spite of the high temperature. Section "6L" was processed in a similar manner, except that the penultimate annealing was much longer, so as to allow considerable grain growth. Section "4" was given the two final

Jan 1, 1961

By R. J. Weege, A. W. Schillinger

Conventional underground mapping methods and diamond drilling are being applied in a study to determine the nature of the copper ore occurrences near the footwall of the Osceola lava flow top, commonly referred to as the Osceola Amygdaloid. The work to date suggests that structures formed by relatively impermeable barriers, created by flowage and injection of still-molten lava from the interior of the flow into the solidified, brecciated crust, acted as the ore receptacles. Ascending hydrothermal fluids traveling near the footwall contact were trapped and confined in these barriers which retarded the direct upward movement of the ore fluids and caused deposition of copper. Oreshoots located near the footwall appear to have been formed spatially independently from the hanging-wall oreshoots by fluids traveling simultaneously, but along different channelways. The barrier concept, as advanced by earlier writers to explain the concentration of the ore-bearing fluids into broad shoots constituting entire ore bodies, is found to be equally as applicable for the localization of smaller oreshoots within the Osceola ore body. Recently, the Calumet Division of Calumet and Hecla, Inc. completed the unwatering of the old mine workings on the Osceola amygdaloid. Two shafts were subsequently reactivated and mining commenced on the Osceola lode after an idle period of over 20 years. Early in 1961, the Calumet and Hecla Geological Dept. was assigned the task of locating additional reserves. Accordingly, an intensive mapping and underground diamond drilling program was initiated. Except for a very few years following the first mining on the amygdaloid, the Osceola lode had never been a high grade producer. It was, therefore, recognized from the onset that a concentrated effort would have to be made by the mining, milling, and geological departments to insure success of the project. Company reports contained many references to ore that had been located near the footwall of the Osceola amygdaloid. Information concerning the grade of this ore was meager, but it was known that at least some was very rich. In contrast to ore that occurred near the hanging-wall, however, the footwall copper did not appear to have a systematic distribution and a large amount of poor rock had to be removed in developing this ore. This, of course, resulted in high development costs and discouraged any extensive mining of footwall ore. The possibility of more continuity than had previously been suspected was recognized by other workers, in particular Dr. T. M. Broderick, formerly Chief Geologist of Calumet and Hecla, who suggested attempts be made on a trial basis to follow the footwall contact with the main development drift. As most mining was done on the Osceola lode before a geological department had been established by the company, and almost all of these openings are now caved, very little information concerning the geology of footwall ore was available. It was, therefore, decided that the first step in the exploration program would be to become familiar with footwall ore occurrences by mapping the geology as the openings were driven. It was possible that a mapping program would reveal the features that controlled the localization of the ore. Furthermore, if it could be shown that footwall ore was more continuous, or if its distribution was more systematic than generally believed, it would be possible to produce a high grade ore that could be blended with the lower grade hanging-wall ore. In connection with the geological program, the Michigan College of Mining and Technology Geophysical Dept. under the direction of Professor Lloyal Bacon, is making a geophysical study of the problems of locating footwall ore by electrical methods. GENERAL GEOLOGY OF MICHIGAN NATIVE COPPER DEPOSITS The native copper deposits of Michigan are located in Keweenaw, Houghton, and Ontonagon Counties. The host rocks are Keweenawan in age and are comprised of interbedded sediments and lava flows which form a belt two to four miles wide and over one hundred miles long. These rocks form part of the south limb

Jan 1, 1962

By Ellis H. Gates

BENEFICIATION of the manganese oxide ores at Three Kids Mine near Henderson, Nev., has evolved over a period of years. Commercial application of the process is on a secure basis, and an effective working hypothesis has been formulated to help solve the problems encountered in flotation. An outstanding difference between the Manganese Inc. operation and other flotation processes is the necessity for high recovery of slime mineral values. Part of the manganese minerals in the Three Kids ore deposit occurs as primary slime or as minerals that are easily slimed by grinding. High recovery of this slime portion is essential to an economic overall manganese recovery. The aim of much of the research at Manganese Inc. was to recover these slimed and finely ground minerals by flotation. Early Agglomeration Processes: Tunbridge' in 1880, followed by Everson2 in 1886 and Cattermole" in 1904, discovered that under certain pulp conditions precious metals and sulfide minerals could be agglomerated if enough soap or oil were mixed into the pulp slurry. These agglomerated particles, Which under ideal conditions ranged from 1/16 to 1/4 in. diam, were recovered by screening, tabling, and hydraulic classification. Even flotation by air occluded in the agglomkrate particles by vigorous stirring was suggested. Cattermole nearly succeeded in getting his process into commercial operation, but it was finally abandoned, presumably because he could nat compete with the low reagent requirements of the new agitation froth process. Since Cattermole's time Christensen in 1921, Borcherdt4 in 1926, and Chapman and Littleford- in 1934 have attempted to apply the principles of agglomeration. In the light of current research at Manganese Inc. on conditioning of pulp at high energy input levels, it is interesting to note the variety of equipment such as tumbling mills, mixing drums, and shakers described by Borcherdt in his patent to produce the agglomerated particles. Ore Characteristics: Manganese in the Three Kids ore occurs as a 'complex mixture of manganese oxides commonly Known as wad. The manganese minerals have Been identified as psilorflelane, hollandite, coronadite, and pyrolusite with minor amdunts of rhodonite and rhodochrbsite. The ppincipal gangue miherals are quaktz, opal, kaolinite, montmoril-lonite, calcite, gypsum, fcelesitite, and barite. Most of the mangandse ore minerals are either porous and sponge-like in structure or soft clay-like masses composed of fine grained mineral particles approaching the size range of colloids. Consequently the ore minerals from the Three Kids mine have relatively large surface areas and high void content per unit weight. The specific area of various manganese ore samples measured at the California Research Corp. laboratories ranged from 32 to 58 sq m per g. The great surface area and high void content explains in part the unusually high reagent consumption required in the treatment of this ore. Current Milling Practice: At Henderson6 he ore is crushed to —1 in. and ground with rod mills in a closed circuit with spiral rake classifiers and cyclones. Sulfur dioxide solution is added to the pulp as it leaves the grinding circuit, immediately followed by addition of a reagent mixture of soap, oil, and wetting agent in the form of an emulsion. The reagents are initially well mixed into the pulp during their passage through centrifugal pumps to the conditioning equipment. All reagents are added prior to conditioning. The intense conditioning or mechanical stirring of the pulp, in which large amounts of power are consumed, is the principal difference between the flowsheet used at Manganese Inc. and a standard flotation circuit. As much as 38 kw-hr of energy per dry short ton of ore in a pulp containing 18 to 23 pct solids is used for conditioning. After conditioning, the pulp passes to a flotation circuit that consists of one roughing stage, a scav-

Jan 1, 1958

By C. N. Reid

Slip-line studies on deformed chromium single cvystals showed the usual bcc behavior. At room temperatuve, cross slip was prevalent—slip was not confined to a given plane, but the slip direction was (111). At -10O0K, slip occuvred on (110) planes, twins on(112) planes, and cleavage on (1001 planes. A single-crystal tensile specimen with an axis close to [011] showed a pronounced yield drop and high strain rate sensitivity which zclere used to derive relevant parame tevs in a dislocation dynamics treatment. Transmission electron microscope studies confirmed the existence of (110) slip planes and showed ecidence of loops punched out by precipitates and of grown-in dislocations promoting tangling. OF recent years experimental studies have been made of the deformation characteristics of single-crystal molybdenum and tungsten, but very little has been published on the behavior of single-crystal chromium. During a study of the mechanical properties of chromium, single-crystal studies were made which have already been partially described.&apos; However, additional information was generated which was not directly relevant to the main theme of Ref. 1, and, therefore, was not reported. In view of the need for complete documentation of deformation modes, the experimental observations made on the deformation of single-crystal chromium are summarized here, together with an electron-microscope study of the associated dislocation structures. It was found that, in terms of the deformation modes, chromium is a conventional bcc metal, showing a very pronounced yield-point phenomenon. Further, it was found that the flow strength of these crystals is very sensitive to the strain rate. Finally, the crystals were observed to contain many unidentified precipitates, which often were associated with prismatic dislocation loops. EXPERIMENTAL METHODS Single crystals were grown from rods of wrought chromium by the method of zone annealing. Rods of "1/4in.-diam were supported vertically in an argon atmosphere while an induction coil was moved up the rod at 1 in. per hr. The power was adjusted to just below that required for melting, and the process produced single crystals in about 30 pct of the rods used. The orientations of the crystals, in general, lay near [011] and are summarized in Fig. 1. Before this treatment, the wrought material contained 35 pprn C, 68 ppm O, and 12 ppm N.* An analyzed single crystal *Usual metallic impurities found in iodide chromium are: Al, 5 ppm; Ca, A ppm; Cu, 2 ppm; Fe, 75 ppm; Yg, 0.5 ppm; Yn, < 3 ppm; Mo, < 3 ppm; Ni, 4 ppm; Si, < 20 ppm; Ti, < 1 ppm; V, 4 ppm; Zr, < 3 ppm. contained 10 pprn C, 79 ppm O, and 50 pprn N. Tension and compression specimens were shaped from the crystals by mechanical grinding, followed by the electrolytic removal of about 0.010 in. from the surface in a perchloric/acetic acid bath. All specimens had a gage length of 0.75 in., and tension specimens had a diameter of 0.100 in., while that of the compression samples was 0.200 in. Mechanical tests were carried out at a rate of 1.3 pct per min, and temperatures below 0°C were attained by means of a nitrogen cryostat similar to that of Wessel.2 EXPERIMENTAL RESULTS Modes of Deformation. In addition to the tensile properties of these crystals, which are described in Ref. 1, deformation markings on the surface were studied. Crystals A and F, Fig. 1, were deformed in tension at 300°K to 10 and 16 pct strain, respectively. The surfaces contained visible slip lines, about 1 C( apart, composed of both straight and wavy segments. They did not define a single plane, and so determination of the slip plane was not possible. However, the slip direction was deduced by comparing the axial orientations of the crystals before and after deformation. Fig. 2 is representative, and shows that the axis ro-

Jan 1, 1968

By P. G. Winchell, J. K. Jackson

The strtcture of body-centered Fe-Ni-C alloys (0 to 16.5 wt pct Ni) containing less than 0.015 wt pct C was investigated by measuring the carbon-diffusion peak at low frequencies with a torsion pendulurrr. By determining the Snoek damping in ferrite and in quenched alloys of identical composition, the effects of nickel content and heat treatment were separated, and the existence of a structure in which Snoek damping is greatly reduced was revealed in the quenched ternary alloys. The relative amount of this structure increases with increased nickel content and cooling rate. It is proposed that this structure may be highly imperfect or tetragonal. In Fe-Ni-C alloys containing only ferrite the addition of nickel (0 to 5.1 wt pet) decreases tke area of the carbon-diffusion peak and shifts its position to lower temperatures but broadens the peak only slightljl. The decrease in peak area with increasing nickel implies that short-range interactions with the nickel atoms prevent some of the carbon atoms from participating in the relaxation process. The shift in the peak position indicates a long-range effect of nickel on the movement of carbon atoms so that at 300°K the diffisivity of carbon in -ferrite is increased by about 35 pct by the addition of 5.1 tut pct Ni. The results are presented as distributions of relaxation strength 072 the activation energy under the assumption that the frequency factor is invariant. BODY-CENTERED iron-base solid solutions dissolve carbon interstitially in the octahedral sites. The occupation of an octahedral site produces a tetragonal distortion of the surrounding lattice. These sites fall into three sets according to the orientation of the tegragonal distortion associated with each and may be identified by their lattice coordinates as: type 1/2 0 0, type 0 1/2 0, type 0 0 1/2. At low carbon levels in cubic ferrite the carbon atoms are distributed at random1 among these sites. In high-carbon body-centered iron-base solid solutions, which are unstable with respect to several two-phase mixtures, a tetragonal structure occurs as the product of the diffusionless transformation of austenite. This transformation is commonly accompanied by appreciable microstrain and its product is called martensite. The tetragonality of martensite, a supersaturated solution of carbon in a iron, is maintained prior to decomposition even though local diffusion of carbon occurs as evidenced by carbide precipitation. The tetragonality is taken as evidence that one set of octahedral sites is preferentially occupied by carbon. (This preferential occupation is called ordering below.) Support for this view is presented by the absence of strain-induced carbon-atom diffusion in high-carbon solid solutions (martensite). Such diffusion occurs in ferrite and produces the 40°C internal-friction peak observed at 1 cps frequencies.&apos; Thus, there appears to be qualitative evidence favoring the view that at sufficiently high carbon levels tetragonality arises spontaneously as a result of the ordering of the carbon atoms; however, no experimental evidence exists concerning an equilibrium between cubic and tetragonal body-centered solid solutions. Moreover, attempts to estimate the energy of ordering7-&apos; predict a value too low to maintain the tetragonality observed at medium carbon levels, 0.3 to 0.6 wt pct C. In the present work an attempt using internal-friction measurements is made to establish the presence or absence of tetragonality in low-carbon body-centered solid solutions formed by quenching austenite. Fe-Ni alloys containing about 0.01 wt pct and 0 to 15 wt pct Ni were selected for the study. While the work was in progress Gilbert and Owen10 reported that the transformation which occurs in these alloys during quenching at rates up to 5000°C per sec is not martensitic but is more properly categorized as massive. Thus, the solid solution

Jan 1, 1964