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By Alexander Squire

One of the principal factors that have contributed to the hesitancy of design engineers to use metal-powder parts is the difficulty experienced in the determination of the mechanical properties of compacted components. Because standard test methods cannot usually be applied in the inspection of such parts, and because adequate special test methods have not been developed, it has been considered desirable to investigate the methods that are applicable. These may then be included in specifications for metal-powder materials and components in order that the design engineer may be assured that the subject parts possess the desired mechanical properties for satisfactory performance. It is known that direct relationships exist between usually nonmeasurable properties as tensile strength and elongation and shear strength and the angle through which compacts may be plastically deformed before fracturing. These correlations are valuable in the inspection of specific parts, but it is necessary to set up standards before they may be satisfactorily employed. Apart from the use of correlations, the number and character of the inspection methods that are applicable to almost all powder parts is limited to three—chemical analysis, density, and hardness. The last of these may or may not be a pertinent characteristic, since the indentation hardness of many powdeied-metal materials is so low as to have little significance. It is, however, occasionally desirable to use hardness measurements as an indication of the uniformity of the structure of pieces of a given type. Chemical analysis reveals very little about the physical properties of metal-powder compacts, since the unpressed powder is usually of a composition almost identical with that of the finished pieces. Density determinations are simple to perform and have the advantage of being nondestructive in character. If the dimensions of a machine part are known (and usually they are), the average density may be determined by weighing a given number of pieces and dividing by the calculated volume of the parts. More accurate measurements may be made by the water-displacement method. It is recognized that mechanical properties of metal-powder materials are related to their density, but usually these relations are determined for only one type of powder, processed under a given set of conditions. Comparisons of the pioperties of compacts formed from different types of powders are made on the basis of compacting pressures instead of density, and for this reason the results obtained by using powders of different types appear widely variant.

Jan 1, 1947

By H. G. Moulton

The increasing scale of mining operations over the past decade, particularly in connection with the exploitation of large bodies of comparatively low-grade copper ores, has made necessary the study of the behavior of rock under failure. When extractions of as high as 40,000 tons a day are reached in steam-shovel operations and as high as 20,000 tons per day in underground mining operations, it is evident that excavations soon become of such size that the behavior of the rock will often be dependent on fundamental principles applicable to more or less homogeneous materials under stress, rather than on weathering or local planes of weakness. In the ordinary rock excavations encountered in civil-engineering practice, such as excavations for subways, highways, railroads, etc., rock faces are not carried to depths sufficient to develop any pressures, or consequently any failures, except those due to loose masses resulting from local planes of weakness. When, however, orebodies whose tonnage is measured by hundreds of thousands are to be extracted by steam-shovel operations in open pits, it is necessary to determine if possible in advance the slopes that the sides of the pits will assume, for these slopes influence the shape of the excavations and thereby the amount of ore that may be extracted by the open-pit method. When large orebodies are mined underground at depths of 300 to 500 ft. (91 to 152 m.) by caving methods, the surface subsiding as the ore is withdrawn, it is necessary to determine in advance the outermost limits of fracture in the subsiding surface, for on the delineation of these limits depends the location of surface improvements, mills, smelters, etc. and also the location of development work, such as hoisting shafts, main haulage levels, and all other underground openings that must remain undisturbed during the period of ore extraction. Heretofore, in civil-engineering practice, it has been assumed that earth and rock behave differently in failure. For the calculation of earth pressures, formulas are used in which the assumption is made that earth banks fail by sliding along the slope determined by the frictional resistance of the material. The line of failure and the resulting pressure is held to be dependent on the angle of repose, which is different for varying

Jan 1, 1920

By W. A. Selvig

BY plotting fixed carbon against British thermal units of coals free from mineral matter, and ranging in rank from anthracite to lignite, it is found that the coals of higher rank, from anthracite to the higher rank of the high-volatile bituminous coals, inclusive, can be separated into groups according to their degree of metamorphism by reference to their fixed carbon. Such charts show also that the coals lower in rank can be best separated into groups with respect to B.t.u., especially when plotted on the moist basis, that is, coal containing its natural bed moisture. A tentative scheme for coal classification was presented at the October, 1932, meeting of the Technical Committee on Scientific Classification, of the American Standards Association Sectional Com-mittee on Coal Classification. This scheme was sponsored by Sub-committee IV on Tentative Classification of Coals, under the chairmanship of W. T. Thom, Jr. It proposed the grouping of coals according to rank by reference to fixed carbon and B.t.u., on the basis of coal containing its natural bed moisture but free from mineral matter. This scheme proposed classifying coals into four broad classes: (1) anthracitic, (2) bituminous, (3) subbituminous, (4) lignitic.. The anthracitic class was divided into three groups designated as meta-anthracite, normal anthracite, and semianthracite. The bituminous class also was divided into three groups, low volatile, medium volatile, and high volatile. The high-volatile group was further subdivided into four subgroups according to moisture content, as follows: (1) less than 5 per cent, (2) 5 to 10 per cent, (3) 10 to 15 per cent, and (4) 15 per cent and more. The subbituminous class was divided into two groups, group, 1 including subbituminous coals having calorific values of 10,500 B.t.u. or more, and group 2 including those with less than 10,500 B.t.u. , The lignitic class of coal was divided into two groups both below 8,000.B.t.u., the one group consisting of consolidated and the other of unconsolidated

Jan 1, 1934

By W. H. Ode, W. A. Selvig

By plotting fixed carbon against British thermal units of coals free from mineral matter, and ranging in rank from anthracite to lignite, it is found that the coals of higher rank, from anthracite to the higher rank of the high-volatile bituminous coals, inclusive, can be separated into groups according to their degree of metamorphism by reference to their fixed carbon. Such charts show also that the coals lower in rank can be best separated into groups with respect to B.t.u., especially when plotted on the moist basis, that is, coal containing its natural bed moisture. A tentative scheme for coal classification was presented at the October, 1932, meeting of the Technical Committee on Scientific Classification, of the American Standards Association Sectional Committee on Coal Classification. This scheme was sponsored by Subcommittee IV on Tentative Classification of Coals, under the chairmanship of W. T. Thom, Jr. It proposed the grouping of coals according to rank by reference to fixed carbon and B.t.u., on the basis of coal containing its natural bed moisture but free from mineral matter. This scheme proposed classifying coals into four broad classes: (1) anthracitic, (2) bituminous, (3) subbituminous, (4) lignitic. The anthracitic class was divided into three groups designated as meta-anthracite, normal anthracite, and semianthracite. The bituminous class also was divided into three groups, low volatile, medium volatile, and high volatile. The high-volatile group was further subdivided into four subgroups according to moisture content, as fo1lows: (1) less than 5 per cent, (2) 5 to 10 per cent, (3) 10 to 15 per cent, and (4) 15 per cent and more. The subbituminous class was divided into two groups, group 1 including subbituminous coals having calorific values of 10,500 B.t.u. or more, and group 2 including those with less than 10,500 B.t.u. The lignitic class of coal was divided into two groups both below 8,000 B.t.u., the one group consisting of consolidated and the other of unconsolidated

Jan 1, 1934

By W. E. Wrather

The overproduction of crude oil in 1927 has received such widespread publicity, both within and without the industry, and the several factors which have brought about this situation are so thoroughly agreed upon by everyone, that it is unlikely the writer will in this brief review be able to contribute anything new. The entire story of low prices and demoralization revolves around two flush districts, Seminole and West Texas— the actual. performance of Seminole and the potential threat of West, Texas. The sustained production of California has been a contributing factor to this situation also. It seems reasonably certain that Seminole and West Texas will together dominate the industry during 1928, with Seminole probably destined to drop into second place, as additional pipe lines are completed into West Texas to care for its rapidly expanding production. It now appears inevitable that the production of 1928 will equal or exceed that of the past year, depending solely upon the rapidity wit,h which it is possible to market West Texas crude, and the degree of restraint which operators are willing to impose upon themselves in holding proved reserves of oil underground. Adversity has cultivated the growth of a promising spirit of cooperation which has accomplished practical results both at Seminole and in West Texas. Cooperation among oil producers has long been ardently hoped for, but prior to the past year it has never been effective on an important scale. The interests both of the industry and the public at large can best be conserved by cooperation in controlling production, and the widespread acceptance of this idea has paved the way for a more rational policy in the immediate future Production BY Major Districts The domestic production of the United States during 1927 amounted to 894,43.5,000 bbl. (Bureau of Mines), an increase over 1926 of approximately 128,000,000 bbl. California succeeded in maintaining its position of the past four years at 230,000,000 hbl. In 1923 with the Los Angeles

Jan 1, 1928

By D. E. Mikkola, G. E. Poquette

X-ray diffraction was used to study the growth of antiphase domains in quenched (or "disordered&apos;? Cu3Au annealed in the range 300" to 385°C. Measurements of the long-range order parameter indicate that a high degree of order is established rapidly at these annealing temperatures. Average domain sizes obtained by Fourier analysis of the superlattice peak profiles show that antiphase domain growth is analogous to classical metallurgical grain growth (i.e.,fol-lows a D2 US kt relation). The activation energy for the growth process, 44 kcal per mole, indicates diffusion control. The anisotropy in the observed effective domain sizes from seven different superlattice peaks can be best accounted for by a configuration involving antiphase domain boundaries on {100 } and (111 ) planes, where the (100) boundary is the low-energy type, {lOO} Type I. The disappearance of the (111) antiphase domain boundary during domain growth is dif-fusion-controlled with an activation energy of 48.5 kcal per mole. On the other hand, the behavior of the parameter representing the amount of (100) Type I boundary indicates that there may be a conversion of the higher-energy boundary types to (100) Type I boundary during the growth process. THE order-disorder transformation in the alloy Cu3Au has been the subject of numerous experimental investigations over the past 40 years, most of which have involved measurements of convenient physical properties such as resistivity and hardness as a function of heat treatment. The interpretation of these data is difficult because measurements of this type have the disadvantage that they yield total changes resulting from several different atomic processes which may be occurring simultaneously. The present study was undertaken to establish by means of X-ray diffraction the kinetic behavior of one of these atomic processes, namely antiphase domain growth. In the completely ordered state Cu3Au has an L12 structure which can be described as an fcc type arrangement of atoms in which the gold atoms occupy the corner sites and copper atoms the face-centered sites. Three other equivalent unit cells can be formed by allowing two gold atoms to occupy opposite face-centered sites and copper atoms to occupy the remaining corner and face-centered sites. These four different unit cells are crystallographically related by a shift of 1/2<110>. Quenching from above the critical temperature (392°C) to room temperature retains the "disordered" structure-a "random" arrangement of copper and gold atoms having the fcc structure. Annealing the disordered alloy below the critical temperature causes ordering to occur through the nucleation and growth of ordered regions at different points throughout the crystal. These small ordered regions, each based on one of the four types of unit cell, grow by consuming the disordered material until they impinge to form a domain structure in which the domains are antiphase by a shift of 4(110). The boundaries between domains are called antiphase domain boundaries (APDB) and they have been found to lie primarily on &apos; {100} planes in highly ordered Cu3Au. Two types of APDB can occur on ( 100) planes. An example of an (001)1/2[110] shear type APDB is shown in Fig. I. Because of the layer of copper atoms separating the domains in this case, there are no near-neighbor violations across the boundary and it has a low surface ener This type of APDB will be referred to as {lOO} Type I. Fig. 2 shows an (001): [011] climb type APDB, (100) Type 11. This type of APDB can be described as resulting from removal of a (200) plane followed by a shift of 1/2<110> to bring the separated regions together. Near-neighbor violations across (100) Type I1 APDB make it a high-energy boundary. There are numerous other possible APDB configurations; however, it is only worth noting that shear type APDB can be produced on the (111) plane by motion of a normal fcc dislocation with Burgers vector 1/2<110> through the ordered structure. A (111); [110] shear type APDB is shown in Fig. 3. Again, because of the near-neighbor violations this type of APDB has a higher energy than the (100) Type I APDB.

Jan 1, 1970

By A. V. Deforest, C. W. Macgregor, A. R. Anderson

One of the important problems in the design of structures and machine parts subjected to rapidly applied loads is the determination of the strength and ductility of the material itself under such conditions. Realizing the need for such information, many investigations have been carried out in the past. Most of these experiments have been made using notched bars in bending either with the Charpy or Izod impact machine. While yielding valuable data on the effect of notches in the energy absorption of the material and on the condition of heat-treatment, this form of test does not lend itself readily to a determination of fundamental stress-strain relations. For this and other reasons, more attention has been paid recently to the tension impact test. An extensive literature already exists on the subject and only those investigations somewhat closely related to the present paper will be mentioned. For a more comprehensive list, the reader is referred to the Symposium on Impact Testing or the A.S.T.M., 1938. The work of Mann.&apos; Clark and Dätwyler,2 Nádai and Manjoine,3 Winlock and Leiter,4 Deutler,5 and Brinkmann,6 however, deserves especial mention. In most of the previous investigations on the subject, when stress-strain relations were obtained under high rates of loading, it was the common procedure to determine stresses based on the original area and strains based on the original length. Stress-strain curves were then constructed by P ALo plotting So = 1/A0 as a function of eo = ALr,o where A0 and Lo refer to the original area and gauge length, respectively. At present there exists a paucity of true stress-strain data in the impact problem. The advantages of constructing so-called true stress-strain curves in order to reveal the fundamental physical properties of the material for the tension test were discussed recently by one of the authors.7&apos;8 It was shown that the true physical behavior of the material in the tension test could best be represented P by plotting the average true stress, S = 2P as a function of 6 = q&apos; = log —r = log ~9L where P, A, L, S, E, and q&apos; refer to the load, the cross-sectioned area while the load P is applied, the actual gauge length, the average true stress, the true strain and true reduction in area, respectively. Besides giving a better physical representation, the method has certain additional advantages in that the stress-strain curve so plotted becomes a straight line from the maximin load point to fracture. The construction of such curves, however, while comparatively simple for the slow rates of loading customarily used in the tension test, presents certain dificulties for tensile impact in that both loads and diameters are required throughout the test. The continuous measurement of test-piece diameters to fracture under impact conditions offers considerable experimental difficulty. In order to make it feasible to

Jan 1, 1942

By A. V. Deforest, A. R. Anderson, C. W. MacGregor

One of the important problems in the design of structures and machine parts subjected to rapidly applied loads is the determination of the strength and ductility of the material itself under such conditions. Realizing the need for such information, many investigations have been carried out in the past. Most of these experiments have been made using notched bars in bending either with the Charpy or Izod impact machine. While yielding valuable data on the effect of notches in the energy absorption of the material and on the condition of heat-treatment, this form of test does not lend itself readily to a determination of fundamental stress-strain relations. For this and other reasons, more attention has been paid recently to the tension impact test. An extensive literature already exists on the subject and only those investigations somewhat closely related to the present paper will be mentioned. For a more comprehensive list, the reader is referred to the Symposium on Impact Testing or the A.S.T.M., 1938. The work of Mann.&apos; Clark and Dätwyler,2 Nádai and Manjoine,3 Winlock and Leiter,4 Deutler,5 and Brinkmann,6 however, deserves especial mention. In most of the previous investigations on the subject, when stress-strain relations were obtained under high rates of loading, it was the common procedure to determine stresses based on the original area and strains based on the original length. Stress-strain curves were then constructed by P ALo plotting So = 1/A0 as a function of eo = ALr,o where A0 and Lo refer to the original area and gauge length, respectively. At present there exists a paucity of true stress-strain data in the impact problem. The advantages of constructing so-called true stress-strain curves in order to reveal the fundamental physical properties of the material for the tension test were discussed recently by one of the authors.7&apos;8 It was shown that the true physical behavior of the material in the tension test could best be represented P by plotting the average true stress, S = 2P as a function of 6 = q&apos; = log —r = log ~9L where P, A, L, S, E, and q&apos; refer to the load, the cross-sectioned area while the load P is applied, the actual gauge length, the average true stress, the true strain and true reduction in area, respectively. Besides giving a better physical representation, the method has certain additional advantages in that the stress-strain curve so plotted becomes a straight line from the maximin load point to fracture. The construction of such curves, however, while comparatively simple for the slow rates of loading customarily used in the tension test, presents certain dificulties for tensile impact in that both loads and diameters are required throughout the test. The continuous measurement of test-piece diameters to fracture under impact conditions offers considerable experimental difficulty. In order to make it feasible to

Jan 1, 1942

By J. L. Bruce, G. W. Nicolson

ThE country rock of the Mavrovouni mine of the Cyprus Mines Corp. is hydro-thern~ally altered, disintegrated pillow lava, with very little tensile strength ("short" ground). In places, especially when wet, it is heavy ground, though not extremely heavy except where movement has been caused by underlying or nearby stoping operations. Damage by caving from roof or sides of galleries is not sudden but progressively faster when the size of the cave increases as a result of the fall of small pieces. CeMent and Concrete Linings During early operations, galleries in the country rock were supported by customary mine-timbering methods. Available timber, howcver, was of poor quality and of relatively high price, and replacements were frequent and expensive. Furthermore, the massive sulphide ore bodies required large volumes of fresh air for ventilation and cooling, and it was therefore desirable to provide smooth-lined galleries with low resistance for the introduction of air to the ore bodies. It was also desirable to eliminate hazards of fire in shafts and underground workings insofar as this would be practical. Cement and concrete were relatively cheap, and plans for using these in support of shafts, underground galleries, raises, and chutes, were developed steadily. Circular shafts with diameters ranging from 10 to 15 ft were adopted for all permanent shafts and airways. In places these were lined with concrete poured behind sectional pressed-steel forms especially constructed for this purpose. In other places, they were lined with precast-concrete blocks. It was found that such precast concrete of good quality could be produced on mass production scale and delivered at the mine from most favorable point of manufacture, at a cost of about 25 cents per cubic foot of concrete. This refers to prewar costs. As the use of concrete blocks in circular lined galleries was developed, it was found that there were very great advantages in the reduction of air resistance as compared with customary timber supports. After best methods had been developed, it was found that breakage and replacements were extraordinarily low, averaging only about 11\2 pct per year during a period of about 15 years. Furthermore, it has been possible to reclaim for re-use a very large percentage of the concrete blocks from abandoned galleries. During the history of the operations precast-concrete blocks have been used for lining shafts, raises, ore chutes, galleries, and shaft stations, ranging from 3 to 16 ft id. The thickness of lining has varied from 5 to 10 in.; with 12 in. thickness in a few cases. Junctions of two galleries at angles ranging from about 30 to 60° are usually made of poured concrete behind sectional forms, or of a combination of poured concretc and precast blocks. In nearly all cases it has been found advisable to make the point of the wedge at the junction, of

Jan 1, 1949

By Gilbert Soler

Producers of alloy steels recognize the importance of chemical composition in relation to the hot-working properties and the typical surface defects found in their product. Each analysis of steel has its own peculiar characteristics. Under conditions of standard mill practice each analysis is susceptible to certain types of defects. Mill practice must be varied to obtain the best combination of surface and internal quality in the product. Chemical composition influences the cast structure and crystallization characteristics of the ingot. It also determines the rate of heating and cooling, the plastic hot-working range, and the phase structure of the steel at various temperatures. as well as the tendency toward scale formation and decarburization. This paper endeavors to emphasize the manner in which chemical composition affects the various properties of steel, and to indicate the relative importance of these factors in relation to the hot-working properties and surface characteristics of killed steel. The influence of chemical composition may be outlined as follows: I. Effect on the cast structure of steel, including: A. State of deoxidation, and type of inclusions. B. Gas content of steel. C. Freezing point and melting point of steel. D. Crystallization characteristics and segregation. 11. Effect on the hot-working properties and surface characteristics of steel, including: A. Plastic hot-working range. B. Phase structures at hot-working temperatures. C. Rate of heating. D. Cooling characteristics. E. Scale formation. F. Surface decarburization. EFferect of Chemical Composition on Cast Structure of Steel State of Deoxidation and Type of Inclu-sions.—The state of deoxidation is limited by the final chemical analysis desired in the finished product, and is controlled primarily by carbon, manganese, silicon, and aluminum, and to a lesser degree by chromium, titanium, vanadium, or other deoxidizing elements. The degree of deoxidation affects the density of the cast structure and broadly classifies the steel as killed, semikilled, or rimming. This in turn manifests itself in surface characteristics. The manner and extent of deoxidation also controls the amount, type, and distribution of nonmetallic inclusions formed. The equilibrium of manganese, silicon and aluminum with the slags and pouring refractories with which the metal comes in contact is important, especially in regard to inclusions of fire-clay origin. Some surface Seams and hot-working difficulties can be traced to nonmetallic inclusions.

Jan 1, 1941

By Gilbert Soler

Producers of alloy steels recognize the importance of chemical composition in relation to the hot-working properties and the typical surface defects found in their product. Each analysis of steel has its own peculiar characteristics. Under conditions of standard mill practice each analysis is susceptible to certain types of defects. Mill practice must be varied to obtain the best combination of surface and internal quality in the product. Chemical composition influences the cast structure and crystallization characteristics of the ingot. It also determines the rate of heating and cooling, the plastic hot-working range, and the phase structure of the steel at various temperatures. as well as the tendency toward scale formation and decarburization. This paper endeavors to emphasize the manner in which chemical composition affects the various properties of steel, and to indicate the relative importance of these factors in relation to the hot-working properties and surface characteristics of killed steel. The influence of chemical composition may be outlined as follows: I. Effect on the cast structure of steel, including: A. State of deoxidation, and type of inclusions. B. Gas content of steel. C. Freezing point and melting point of steel. D. Crystallization characteristics and segregation. 11. Effect on the hot-working properties and surface characteristics of steel, including: A. Plastic hot-working range. B. Phase structures at hot-working temperatures. C. Rate of heating. D. Cooling characteristics. E. Scale formation. F. Surface decarburization. EFferect of Chemical Composition on Cast Structure of Steel State of Deoxidation and Type of Inclu-sions.—The state of deoxidation is limited by the final chemical analysis desired in the finished product, and is controlled primarily by carbon, manganese, silicon, and aluminum, and to a lesser degree by chromium, titanium, vanadium, or other deoxidizing elements. The degree of deoxidation affects the density of the cast structure and broadly classifies the steel as killed, semikilled, or rimming. This in turn manifests itself in surface characteristics. The manner and extent of deoxidation also controls the amount, type, and distribution of nonmetallic inclusions formed. The equilibrium of manganese, silicon and aluminum with the slags and pouring refractories with which the metal comes in contact is important, especially in regard to inclusions of fire-clay origin. Some surface Seams and hot-working difficulties can be traced to nonmetallic inclusions.

Jan 1, 1941

By C. H. Li, R. J. Stokes, T. L. Johnston

Sodium chloride crystals are brittle in the presence of surface microcracks. Water immersion leads to an enhancement of ductility which is retained indefinitely in dry air providing the crystal is dried without leaving a surface precipitate. Storage in a damp atmosphere results in a surface reaction and consequent rembrittlement. Although elimination of surface flaws in ionic solids does not necessarily enhance ductility, there is always a change in the location of the fracture origin. EVER since the original experiments of Joffel there has been controversy over their interpretation and no satisfactory generalized explanation has yet been given. It is generally admitted that when sodium

Jan 1, 1961

By A. G. Metcalfe

Observations at temperature are used to investigate the phase changes in alloys containing more than 50 pct Co and above 1000°C. The nonsuppressible transformations in cobalt above 1120°C and in the intermetallic compound Co2Cr3 are studied. The liquidus and solidus surfaces are determined. Insufficient data is obtained to complete the constitution diagram. A REVIEW of some of the earlier work on cobalt&apos; and on the binary systems with chromium2-4 and with molybdenum,5 showed that one likely source of differences might be attributed to the presence of phases at high temperatures which could not be retained by quenching. Consequently, the decision was made that only methods of examination at temperature should be used in this work. The correctness of this decision was confirmed during the course of the work by the investigation of the martensitic nature of the transformation in cobalt- and by the decomposition of the high temperature form of the phase Co2Cr3 on quenching.&apos; The use of high temperature methods, including dilatometry and thermal etching led to the postula-tion of the existence of a high temperature form of cobalt with a probable hexagonal close-packed structure, transforming from cubic cobalt over a range of temperature from 1119° to 1145°C.8 One of the important pieces of evidence for this transformation was that it was observed in alloys with chromium and molybdenum which were nonmagnetic at this temperature so that confusion with magnetostriction effects was impossible. These results were not reported in this earlier paper, so that the data given here supply further evidence for the existence of a second allotropic transformation in cobalt. High temperature observations are necessarily much slower in producing results than the examination of quenched specimens at room temperature by conventional means such as X-ray diffraction or microexamination. The investigation has only covered a limited part of the field, as a result, extending from the liquidus down to about 1050°C and from the cobalt corner up to 50 pct alloying elements. The differences between the various reported diagrams for the constitution of the Co-Mo and Co-Cr systems have already been mentioned. The best available diagram in the first system is due to Sykes and Graff&apos; which is shown in Fig. 1. Fig. 2 shows the latest Co-Cr diagram due to Elsea, Westerman, and Manning.&apos; A comparison reveals that these are incompatible because of the disagreement with regard to the number of allotropes of cobalt. Elsea, Westerman and Manning took their liquidus and solidus curves from Wever and Haschimoto.2 The temperature horizontal in the two-phase field beneath the eutectic was placed 35" to 39°C higher than in earlier work2,4 with a new interpretation of the nature of this transformation. This interpretation also required a peritectic horizontal at about 1470°C, which has been confirmed here for an alloy with 53 pct Cr. No investigation had been made of the ternary system until after this work had been terminated, when a section at 1200°C was published." In this work a ternary compound was found by the X-ray diffraction examination of quenched alloys. This compound contained less than 50 pct Co, and was thus outside the field investigated here. However, some reactions were found dilatometrically which could not be fitted on the diagram and are now believed

Jan 1, 1954

By B. R. Banerjee

MATERIAL used throughout this investigation was high-purity aluminum (99.998 pct). The 1/2-in. cubes were cut out of a cold-rolled slab and annealed at 550°C for 1 hr before deformation. The single crystal specimen was 1 in. in diam x 0.33 in. thick, cut from a cylindrical crystal produced by cooling at about 55°C per hr in a furnace which had a convenient gradient of about 10°C in every 4.5 in. vertical crucible length. Specific data on the ten specimens studied are summarized in table I. Three types of deformation were employed: (I) compression in a hand-operated hydraulic press; (2) impact with a 7-lb sledge hammer; and (3) rolling, using a wedge-shaped specimen&apos; to obtain a gradient of deformations varying from 0 to 50 pct along the length of the wedge. Specimens were either deformed at room temperature, or first cooled in a freezing mixture of dry ice and ether at a temperature of —72°C and then deformed between steel blocks cooled with dry ice. The specimens deformed at the low temperature were ground and polished through 000 emery paper and wheels impregnated with alundum and alumina No. 1. During this entire procedure the specimens were dipped frequently in the freezing mixture of dry ice and ether in order to maintain constantly a frosty surface as insurance against overheating. All specimens were given a final electrolytic polish, using two different electrolytes* to insure that the surface effects observed were not char- acteristic of the polishing technique. With both electrolytes, the annealed specimens gave even surfaces with good polish. Several standard etchants were tried without success. The best results were obtained with an immersion etchant, developed in this connection, containing: hydrofluoric acid, 4 parts; nitric acid, 1 part; glycerine, 3 parts. Discussion of Results Typical strain markings have been observed within deformation bands, as shown in figs. 1, 2, and 4. By stereographic plotting of metallographic measurements, the strain markings within a deformation band in a single crystal of aluminum deformed by compression were found to be traces of (111) planes within a maximum scatter of 6". The edges of the deformation band were found to be traces of the (100) planes also within the maximum scatter of 6" (in agreement with previous workers). At 30 pct deformation, this scatter was considered quite normal because of the fragmentation and rotation of the crystal. This solution, based on the traces on one plane of observation is not unique, but as the planes were observed to be those normally and logically to be expected, further work in this regard was not felt to be necessary. The study of strain markings in a wedge-shaped specimen, rolled to obtain a gradient of deformation from 0 to 50 pct, revealed prominent strain markings at 25 pct reduction in thickness (fig.5). Faint and weak strain markings were visually observable up to a minimum reduction in thickness of about 12 pct. Since strain markings have been observed in other face-centered cubic metals after much smaller deformations;1, 2 and since the rate of recovery in aluminum is high, it is believed that, at lower deformations, self-recovery removes the localized strains at the slip interfaces, thus removing the source of the etching effects that give rise to strain markings. At high magnifications, strain markings sometimes seem to appear as very thin, light-banded re-gions bounded by a pair of dark edges. This so-

Jan 1, 1951

By K. BRUCE DAVIDSON

-The North Central Texas area includes the following counties in Railroad Commission of Texas District 7-B: Brown, Callahan, Coleman, Comanche, Coryell, Eastland, Erath, Fisher, Hamilton, Haskell, Hood, Jones, Lampasas, Mills, Nolan, Palo Pinto, Parker, S

Jan 1, 1946

By G. Krauss, W. Pitsch

The fine structure of the bcc martensite formed in an Fe-33 wt pct ATi single crystal of arrstenite is sho~on by transmission electron microscoPy to consist of combinations of transformation twins, stacking faults, deformation twins, and regular arrays of parallel screw dislocations. These structures constitute evidence for the multiple lattice-invariant deformations which operating during the formation of martensite could produce the real habit-plane scatter measured by a two-surface analysis of the plates formed in the single crystal of this investigation and reported in the literature for other Fe-Ni rnartensites. CRYSTALLOGRAPHIC theories1,2 of martensitic transformation show that the habit plane of martensite in a parent lattice is dependent in part upon an inhomogeneous distortion or lattice-invariant deformation which takes place on a fine scale within a martensite plate during its formation. Several recent theoretical papers3,4 have addressed themselves to an analysis of a wide variety of conceivable lat-tice-invarient deformations and the habit planes which they produce, while experimental investigation have been concerned with either the measurement of habit planes or the description and identification of the martensitic fine structure which reflects the nature of the lattice-invariant deformation operating during transformation. In Fe-Ni alloys with subzero Ms temperatures, the group of alloys with which this paper concerns itself, habit planes have often been found to scatter an amount greater than might be expected from possible experimental errors,5-7 and fine twinning has been identified as a major constituent of the fine structure of martensite.8-11 It has been suggested3,4 that more than one type of invariant shear occurs during martensitic transformation. This possibility has been experimentally supported12,13 by the observation of both dislocation configurations and twinning in a single martensite plate. The purpose of this paper is to report additional evidence for multiple lattice-invariant deformations in martensite and so to account for the real scatter in the habit planes of the martensite plates formed in Fe-Ni alloys. EXPERIMENTAL PROCEDURE The Fe-Ni single crystal was produced by pulling a high-purity iron and nickel charge through a single-crystal vacuum furnace in an alumina crucible. The crystal was double-melted to promote homogeneity and to increase its size by further additions on the second pass. In its final form the crystal was 4 cm in diam and 5 cm long. The nickel and carbon contents were analyzed at 32.9 and 0.006 wt pct, respectively. The austenite of this alloy first transformed to martensite by bursts at about -120°C, and, to preserve as much of the austenite as possible, all transformation was performed just below -120°C. Some observations were made on transformed samples which had been heated for 2 min at 340°C. It is assumed that the features of the martensite of these samples, Figs. 1 and 4, are the same as those of the as-quenched martensite. Orientation of the crystal by X-ray diffraction established 10.735 0.609 0.3161? as the axis of the crystal, an orientation that was checked within 2 deg by neutron diffraction. Further checks by electron diffraction of samples cut normal to the axis confirmed this orientation within the larger limits of error inherent in electron diffraction of thin foils. The X-ray orientation was the one used for the two-surface analysis of the martensite habit planes. A two-surface analysis was performed on the quadrant of the single crystal which had been oriented by both X-ray and neutron-diffraction techniques. Photomicrographs at X50 were made on two surfaces along an edge 2 cm long. Fiducial marks and the fact that many of the plates were almost completely surrounded by retained austenite made good matching of individual plates on two surfaces possible. The habit-plane trace on a surface was taken as the best line parallel to the long axis of a plate. A measure of the accuracy afforded by this criterion was provided by a family of very large plates which appeared at intervals along the entire 2 cm length of the edge. The plates all had habit-plane traces within 2 deg of one another. Many of the plates did not show midribs and, therefore, the use of midribs7 to represent habit-plane traces was not feasible in this investigation. The over-all experimental accuracy is estimated to be better than ±2 deg. Samples for transmission examination in a Siemens Elmiskop I at 100 kv were prepared by cutting 2-mm-thick discs from the single crystal, removing about 0.5 mm by chemical polishing,14 trans-

Jan 1, 1965

By Dever C. Ashmead

Anthracite was first mined in the Wyoming Valley and sold as an article of commerce in 1808. As some preparation has always been necessary to make it ready to burn, the preparation of anthracite must date back over a hundred years. Two vital factors have determined to a large extent the degree and the method of anthracite preparation. These are, first, the character of the beds worked and the methods by which they are mined and, second, the equipment used and practices followed in the burning of the coal. It is not the intention here to go deeply into these phases of preparation as a paper of no mean length could be prepared on the history of either. Rather, the intention here is to point out the main considerations and to show the influence they have exerted on the preparation of anthracitc. Mining Methods and Their Relation to Preparation In the beginning of the nineteenth century, the coal beds were virgin with the possible exception of some outcroppings that had been worked, to a slight extent, by the Indians. It is known that the American aborigines had a, knowledge of the use of this fuel, because when the Wyoming Valley was purchased from them, in 1754, they mentioned the fact that, by selling the land, they would lose their coal. Real mining of anthracite began about 1808 when Judge Jesse Fell, of Wilkes-Barre, discovered that the "common stone coal of the valley" could be burned in an open grate. For some years thereafter mining was conducted near the surface. The working p1aces were driven narrow; only the best of the coal was selected and the remainder was left in the ground. Only the lumps could be used, as no market existed for other sizes. As time passed, however, it became necessary either to go farther into the ground or to widen the working places. When these places were widened, falls of roof were apt to occur, making it necessary

Jan 1, 1922

By G. S. Cole, G. F. Bolling

A series of Al-Cu alloys has been cast from constant superheat to solidify either with a hot top or with a free liquid/air interface. All the other variables which affect relative fluid motions were kept constant except the imposition of slow rotations m oscillations of the mold. Depending upon the exact circumstances, evi-dence could be found for the nucleation of equiaxed grains from dendrite bits detached from the columnar zone, or from the free surface, or from solid bits induced at pouring; a special experiment showed the solute buildup during ingot solidification and by inference the reality of constitutional supercooling. All methods of grain nucleation are thus supported. When solidification is arranged in a static mold the columnar- to-equiaxed transition occurs by one of these nucleation paths, subject to the natural decay of temperature gradients which promotes nucleation or the survival of nuclei. But when solidification is forced under special fluid flows it may display odd transitions. In one of these the equiaxed zone is synihesized from. dendrite bits detached from the solid/liquid interface. These survive under the concurrent lowering of temperature gradients and eventually cause transition by impeding columnar growth. GRAIN structure control is desired because real experience shows that specific properties are associated with specific cast grain structures. But since control is thus a matter of need and does not require understanding, much of casting remains art. For example, the manipulation of relative fluid motions in simple ingots provides a control of grain structure development,1-4 but theoretical insight is not required in order to broaden its potential applicability. Fortunately, however, once a variable like fluid flow is recognized it can also provide paths toward new insight. New observations using this variable have provided an insight which is curious. All the theories or descriptions of the columnar-to-equiaxed transition (CET) seem to be supported as long as the appropriate experiment is carried out. In order to develop this idea, let us ignore segregation, the chill zone (until a later section of this paper), and the origin and development of the columnar zone.= The details of questioning how equiaxed material forms in a casting may be divided in two. The first part is simply a questioning of the origin for equi-axed grains: are there fresh nuclei from heterogeneous nucleation, or dendrite bits broken off or melted from the columnar zone or elsewhere,6 or other solid bits surviving from the outset of freezing? The second is more complex, a questioning of the CET: does columnar growth slow down and allow the dominance of equiaxed grains, however they are formed, or do equi-axed grains take over and force columnar growth to stop? This "chicken-or-the-egg" second question can be quite useful, especially because it allows us to delineate the ordinary or NATURAL EQUIAXED ZONE and the induced or SYNTHETIC EQUIAXED ZONE. A natural equiaxed zone occurs if solidification proceeds in the absence of disturbances or extraneous forces such as ultrasonics, stirrings, and so forth. Both the CET theory proposed by Winegard and Chal-mers, 7requiring constitutional supercooling, and the CET theory suggested by Chalmers,8 requiring nuclea-tion only on pouring, pertain to the natural equiaxed zone. The best collating evidence to date for both these theories is contained in the work by Biloni and Chal-mers;9,10 the former theory7 is supported by special versions of the unidirectional growth experiment performed by Plaskett and winegardl1 and the latter theory&apos; is supported in detail for the solidification of small ingots. An equiaxed zone can be synthesized when disturbances caused by forced fluid flows2-4 or other artificial means9,10 break off or melt off dendrite tips from an advancing solid/liquid interface,* if (and only if) temperature gradients in the melt are (forcibly) reduced enough to ensure the survival of these bits of dendrites, 2&apos;3 Willful disturbances even so trivial as those produced by rapping a mold might be included here; as will be shown for example, this follows Southin&apos;s suggestion that the free liquid/air interface

Jan 1, 1970

By C. A. Eligwe, F. W. DeVries, A. E. Torma

This study is an investigation on using hydrogen peroxide for tank-leaching of uranium with sulfuric acid. The optimum sulfuric acid concentration was found to be 0.03 mole 11 -&apos;for a 25% pulp density suspension. The order of reaction with respect to sulfuric acid concentration was found to be ns0.75. The best results vith hydrogen peroxide were obtained at a 4.64 molar ratio of 6202 to U in the ore. The order of reaction was found to be zero with respect to hydrogen peroxide concentration. The theoretical maximum rate effect of Hz02 on uranium extraction was derived as Vm = 8.15 x mole &-&apos;min-&apos;. The highest rate experimentally attained was 8.09 x mole kL&apos;min-&apos;. It was found that the uranium extrac- tion was not affected by the pulp density up to the 50% used in this study. However, the final yieldswere significantly higher (over 90%) for leaches carried out in the presence of Hz02 than (less than 90%) for leaches carried out in the absence of H202. The reaction was found to follow a first order course with respect to substrate concentration (pulp density) regardless of the presence of H202. The effect of temperature was more explicit at moderate tempetatures (30 to 55 C) than at lower (10 C) or at higher (70 C) temperatures. At this latter temperature an almost complete extraction was realized even without H202. The apparent activation energies were found to be AEa = 2.68 kJ mole-&apos; in the absence of H202, 0.5 kJ mole-&apos;with Hz02 at 40 C to 70 C. and 4.72 kJ mole-&apos; with Hz02 at 10 C to 40 C. All these activation energy values suggested that the uranium extraction process is diffusion controlled regardless of the presence of H202. Further, the change in activation energy in the presence of Hz02 indicates the possibility of change in the reaction mechanisms at lower and higher temperatures.

Jan 1, 1980

By R. W. Heckel, R. L. DeGregorio

The DeHoff method of determining the size distribution of ellipsoid-shaped, second-phase particles has been applied to the spheroidization of cementite in a eutectoid steel. The surface area of Precipitates determined from the various size fractions in the distribution was correlated with surface-area measurements based on the number of intersected interfaces on a random lest line. The precipitate particles were found to be oblate ellipsoids with an axial ratio of about 0.90. The size distributions were found to be log-normal. A method is proposed whereby the shrinkage of small particles and growth of large ones can be determined from the experimental data. The experimental data are compared to previously proposed mathematical models describing diffusion-controlled kinetics and various types of interface-controlled kinetics. The experimental growth and shrinkage rates are considerably slower than those predicted by diffusion-controlled kinetics. The best fit is obtained for a model describing interface-controlled kinetics limited by the rate of formation of cementite at the growing interfaces where the interfacial reaction rate is proportional to the solute thermodynamic activity gradient across the surface. THE subject of spheroidization of second-phase particles has been considered previously by other investigators. Livingston1 has studied the precipitation of the cobalt-rich phase from copper alloys containing 0.7 to 3.2 wt pet Co. His results indicate that the average particle size increases as the cube root of the heat treatment time in accord with diffusion-controlled kinetics.&apos;-&apos; Komatsu and rant&apos; in their studies of the growth of SiO2 in a dispersion-strengthened copper-silica alloy found that the initial growth of SiO2 proceeded by diffusion-controlled growth and later stages were limited by interface-controlled growth. The values of the activation energy obtained for the interface- controlled process led them to the conclusion that the process was limited by the dissociation of SiO2 at the shrinking interface. The transition from diffusion-controlled growth to interface-controlled growth was characterized by a particle size which varied with the heat-treatment temperature. It is also interesting to note that the particle-size distribution as found by Komatsu and Grant exhibits log-normal behavior when replotted on log-probability coordinates. Dromsky, Lenel, and Ansell9 have observed the growth of Al2O3 particles having a mean free path of about 1.5 to 13 µ. Their photomicrographs indicate that the Al2O3 particle sizes were larger than those observed by Komatsu and Grant. Dromsky, Lenel, and Ansell concluded that the Al2O3 coarsened by an interface-controlled growth mechanism limited by the solution of A12O3 at the shrinking interfaces. Bannyh, Modin, and Modin10 have studied the spheroidization of a eutectoid steel (0.83 wt pet C). Their spheroidization (tempering) treatments were carried out in the range from 210o to 700°C for times between 1.5 sec and 20 hr. Measurements of mean particle size as a function of time indicated a cube root of time dependence of size at 700°C, in agreement with previous analyses of diffusion-controlled kinetics.2°7 At lower temperatures, the time dependence was less than the one-third power. It is important to note that, although mathematical models of growth* considering particle-size distribution have been available, measurements of only mean particle size have been carried out. DeHoff11 has presented a quantitative metallography technique which is applicable to the determination of the size distribution of ellipsoids of constant shape. This method is applicable to both oblate and prolate ellipsoids of all ratios of minor to major axis and is based upon an extension of Saltykov&apos;s analysis12 of the distribution of spheres of varying size. DeHoff&apos;s analysis is based upon measurements of the minor axis of the particles on a random plane of polish in a unit area. This method provides a measure of the number of ellipsoids in various size ranges per unit area. As pointed out by DeHoff, such measurements may be used to obtain surface area and total precipitate volume data. Thus, the accuracy of the distribution analysis may be checked by comparison of the surface and volume

Jan 1, 1965