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By R. M. Brick, Arthur Phillips

The normal method of preparing metallic alloys for commercial use involves the preparation of a melt containing the given components in the chosen proportions and allowing the homogeneous liquid mass to solidify in a mold of the desired form. The solidification is frequently accompanied by a segregation of the alloying elements in different parts of the casting. When the segregation is occasioned primarily by marked differences in density of the solid and liquid phases, it is termed "gravity" segregation. When the segregation conforms to a selective freezing in harmony with the teachings of the equilibrium diagram of the alloy system—i.e., the lower melting phases are concentrated in the regions of the casting last to freeze—it is often referred to as "normal" segregation. However, in many cases the lower-melting part of the system is concentrated in the parts of the casting first to freeze and the result in this case is termed "inverse" segregation. To complete the terminology of the subject, normal segregation in a single phase is usually called "coring" and the word will be used in that sense in this paper. Inverse segregation, particularly when the liquid phase is exuded or sweated out on the surface of the casting, is sometimes called "liquation." Unfortunately, some ambiguity has arisen from the use of this term and it is perhaps advisable to confine its use to the dictionary definition; namely, "The separation of two phases by heat sufficient to melt one but not the other." The gravity and normal types of segregation are both well understood and to some extent, are controllable by taking advantage of the most favorable cooling rate for a given casting condition. Inverse segregation has received considerable attention from several investigators but none of the theories offered seem to account in a convincing way for the many examples of this type. The observations made in the present work on segregation in single crystals, and in some other castings, tend to support one theory of the mechanism of inverse segregation and definitely to

Jan 1, 1937

1. Book reviews Mill Operators' Conference. Parkville (Australia), Australasian Institute of Mining and Metallurgy, 1982. 425 pp. Reviewer: B. K. Loveday Off highway truck haulage. Newman Combined Group, the Australian Institute of Mining and Metallurgy and the Institute of Engineers in Australia. Sep. 1982. Reviewer: B. J. Vorster Environmental engineering in South African mines.Johannesburg, Mine Ventilation Society of South Africa, 1982. 974 pp. Reviewer: A. N. Brown Underground Operators Conference. West Coast Tasmania Branch. Australasian Institute of Mining and Metallurgy. Reviewer: D. R. Aspeling 2. New publications Electric steelimaking in the eighties: challenges and opportunities. Rotterdam, Balkema, 1982. 362 pp. $50.00 or £33. Tungsten: a review, by P. M. Harris and D. S. C. Humphreys. London, Institution of Mining and Metallurgy (Occasional Paper 2), 1983. Members: £3, nonmembers £6. The platinum industry - prospects in recovery. London, Shearson{American Express Ltd (St. Alphage House, Fore Street, London EC2Y 5DA), 1983. £75. The best of E&MJ mining and processing idea book' New York, Engineering and Mining Journal, 1983. 128 pp. Free with subscription to Engineering and Mining Journal. Mining 1983. Harlow (U.K.), Longman Group Limited, 1983. 500 pp. £39.50. Ooncise guide to world coalfields. London, World Coal Resources and Reserves Data Bank Service (14/15 Lower Grosvenor Place, London SW1W OEX), 1983. 380 pp. £45. 3. Canadian publications Asbestos, by G. O. Vagt, 9 pp. Ooal and Coke, by J. A. Aylsworth, 16 pp. Orude oil and natural gas, by R. L. Thomas, 12 pp. Phosphate, by G. S. Barry, 8 pp. Rhenium, by S. A. Hamilton, 3 pp. 4. Mintek reports Report 2102D The recovery of magnesite from dump fines from the Strathmore Mine. (First issued Feb. 1981.) Report 2106D The evaluation of drill cores and a bulk sample from a deposit of andalusite near Thabazimbi. (First issued Mar., 1981.) Report 2108D Evaluation of a grinding aid in batch grinding, classification, and gravity concentration. (First issued Jul. 1981.) Report 2109D The evaluation of an andalusite deposit from Kleinfontein, Groot Marico. (First issued Apr. 1981.) Report M7D The beneficiation of chromite ore from the Ma-l seam near Marikana. (First issued Nov. 1981.) Report M62 A preliminary investigation into the extraction of zinc by direct oxidative leaching of high-manganese sphalerite. Report M76 A mineralogical investigation of a refractory gold ore, and of a sulphide concentrate and calcined tailing from that ore. Report M85 List of unrestricted Mintek publications issued from 1966 to 1982. Report M97 Reduction in metal consumption by the use of alternating lines of higher and lower lifter bars in a rod mill. Report M98 Multivariable control and optimization of the operation of a milling circuit at East Driefontein Gold Mine. Report M101 The potentiality of heat-treated balls in the grinding of gold ores. X-ray diffraction The Southern Transvaal Section of the South Mrican Chemical Institute is to present a mini-course on 'X-ray Diffraction: Theory and Application' in Johannesburg on 18th and 19th October, 1983.

Jan 1, 1983

By D. B. Masson

THE martensitic transformations occurring in ,B AgCd as a result of cold working at room temp.. a-ture and cooling below room ten1erature have been reported by Masson and Barrett.1 These authors found that simple cooling to 127°K caused body-cen-tered-cubic AgCd containing 53.0 at. pct Ag to transform to an orthorhombic structure, while mechanical deformation at room temperature was found to induce a hexagonal structure. Furthermore, they observed that the temperature at which martensite first appeared on cooling, Ms, and that at which the transformation was complete, MI, as well as the corresponding temperatures for the reversion on heating, As and Af, could be ascertained to ± 1°K, although they report these temperatures only for the alloy containing 53.0 at. pct Ag (51.96 wt pct). In the work reported here the temperature range of the transformation on cooling was studied as a function of composition, and further consideration was given to the relationship between the original bcc structure and the transformation-induced hexagonal and orthorhomic structures. EXPERIMENTAL PROCEDURE All samples studied were in the form of annealed 300-mesh powder and were prepared from the constituent metals in the manner described previously.1 The compositions in weight and atomic pct are listed in Columns 1 and 2 of Table I. Method of determination of transformation temperature was the same as utilized previously1—measurement of the intensity of X-rays diffracted by the transformation product. A diagram of the low-temperature sample mount is shown in Fig. 1. This mount was made to fit a GE model XRD-3 X-ray diffraction unit. The powder sample was varnished to a flat surface on a copper sample holder at A. This sample holder was soldered to a brass rod, B, which was in turn soldered to a second copper rod, C. Rod C could be cooled to 78°K by inserting it into a reservoir of liquid nitrogen, D. A heater coil of nichrome wire was wound at E on the sample holder, and by varying the current through the heater a thermal gradient could be maintained along brass rod B. Sample temperatures from 78°K up could be attained and held as long as needed. The sample holder and nitrogen reservoir were insulated by Styrofoam, F, and the sample itself was protected by two radiation shields, G. The X-ray beam entered and left the sample chamber through windoys in the supporting container at H and I. Sample temperatures were measured by a calibrated copper-constantan thermocouple varnished to the sample holder just out of the beam at A. The low-temperature structure had been found to possess orthorhombic symmetry1 and the expected positions of the diffraction maxima were known. Therefore the sample was aligned in the X-ray beam and the Geiger counter of the spectrometer set to receive the most intense orthorhombic reflection without an adjacent interfering cubic reflection. This

Jan 1, 1961

By Walter Miller

Crude oil stocks were some 10,000,000 bbl higher on June I, 1947, than at any time during 1946 but the extremely heavy refinery runs the last half of 1947 cut crude inventories to approximately the 1946 closing level of 225,000,000 bbl. Many refiners were seriously short of crude oil during the year. This shortage was reflected in numerous advances in the posted price of crude, justified in part as an incentive for more production but more generally due to competitive bidding. Some purchasers of crude, endeavoring to keep their plants running, resorted to the payment, either directly or indirectly, of premiums above the posted price. Another common practice employed by some suppliers of crude oil was to demand refined products in exchange or trade for their raw material. The refined products picture has darkened in spite of record throughputs. Stocks of gasoline and light and heavy fuel oils were uncomfortably low at the beginning of the year and were in general still lower at the close. The rationing of some products, principally gasoline, to dealers and stations? initiated during the year, gained momentum as stocks continued to diminish. The emphasis placed by the manufacturers of oil-burning equipment on the convenience and economy of heating with oil, together with the tight situation in coal, has developed a tremendous demand for burning oils. Consumption of liquefied petroleum gas for domestic and household fuel had more than doubled in 1946 over 1943, and the demand seems to be limited only by the ability of the equipment builders to furnish necessary storage. transportation, and burning equipment. The supply situation is likely to become more acute in 1948. Demand for petroleum products is being pushed to new heights not only by the unprecedented domestic market but by a sudden and drastic upswing in estimates of military and governmental requirements. Additionally, oil exports are running far below the volume requested, amounting to less than forty percent in a recent quarter, and export licenses are reportedly being approved on the basis of urgent need *only. AX recent White House release sees little likelihood that estimated requirements of the sixteen nations participating in the proposed Marshall Plan can be met in full over its projected life—1948 to 1951. Present demand dictates maintenance of refinery operations at the highest possible level and the Bureau of Mines has forecast daily average crude runs in 1948 of 5,265,000 bbl. The Economics Advisory Committee of the Interstate Oil Compact Commission recently estimated the 1948 demand for petroleum products at nearly 6 pct above 1947. They further estimate daily average crude runs of 5,375,000 bbl in 1948, some 2 pct higher than forecast by the Bureau of Mines. Projected demand exceeds supply to the extent that Capitol Hill is reportedly investigating ways of enabling oil companies to act in concert without danger of antitrust prosecution, such as elimination of crosshauls, pooling of products, and lowering of octane.

Jan 1, 1948

By Ronald C. Koo

THE effect of grain size on the mechanical properties of the bcc metals has been a subject of intensive theoretical and experimental study.'-l5 Quantitative relationships have been established experimentally between yield stress and grain size and between the ductile-brittle transition temperature and grain size in a number of metals.6"15 Much significance has therefore been attached theoretically to the grain size dependence. In all these experiments, different grain sizes were always achieved by annealing specimens at various temperatures. The implicit assumption was that any change in the dislocation substructure or in the distribution of impurities which might occur simultaneously with the production of various grain sizes had only a negligible effect on the mechanical properties. The validity of this assumption, however, is questionable. transformation in iron-nickel alloys is actually an extraneous phenomenon due to inadvertent compositional changes in the martensite if the heating rate is not sufficiently rapid. This complication can be avoided by up-quenching for the reversal treatment,5 and then the stabilization does not appear. Clearly, the lattice imperfections and strengthening produced by the reverse transformation are not responsible for the marked stabilization which has been observed by other investigators in these alloys. Data will be presented in this note to show that, at least in recrystallized tungsten of commercial purity, the difference in the ductile-brittle transition temperature of specimens annealed at various temperatures is more a result of a variation in the distribution of impurities rather than of the difference in grain size produced by the anneal. Ductile-brittle transition temperatures in tension were determined on powder-metallurgy tungsten specimens recrystallized at various temperatures. Tensile specimens having a gage length of 1.50 in. and gage diam of 0.18 in. were recrystallized at 1450°, 2000°, 2350°, 2550°, 2750°, or 2800" for 30 min in a vacuum furnace at a pressure of 1 x 10"5 mm of Hg and then tested at a constant extension rate of 8 x 10 per sec in an argon atmosphere from 100" to 800". Typical quantitative analyses of impurities are given in the Table. These results show that, within the precision of the analyses, see Table, annealing did not result in any detectable change in the impurity contents of the specimens, nor was there any detectable difference in purity between specimens having large differences in grain size annealed at the same temperatures . The results of the tensile tests yielded three distinct ductile-brittle transition curves approximately 225' apart. As shown in Fig. 1, data of specimens annealed at 1450°C and those of specimens annealed at 2000°C (O) fell on Curve A. Data of specimens annealed at 2350" and 2550°C fell on Curve B, and those of specimens annealed at 2750" and 2800°C fell on Curve C. The decrease in ductility with increase in annealing temperature became so pronounced that one third of the specimens annealed at 2750" and two thirds of the specimens

Jan 1, 1963

By G. A. Colligan, G. L. F. Powell

A new experimental technique has been developed to study nucleation behavior in eutectic alloys. It is somewhat similar to that applied by Sundquist and Mondolfo1 but with the advantages that: 1) bulk samples are undercooled instead of small droplets thus allowing the thermal behavior to be monitored by a thermocouple immersed in the sample, and 2) nucleation behavior is investigated in the same sample on either side of the eutectic composition by adding additional component to the sample under controlled conditions which preclude the addition of nu-cleation contaminants. Sundquist and Mondolfo carried out ]nucleation ex-periments on a large number of eutectic alloy sys-tems and concluded that nonreciprocal nucleation operated. If one phase a was a good nucleant for the other phase 0, then B was a poor nucleant for a. This was determined experinlentally by comparing the nucleation temperatures of 100 to 300 u diameter droplets of hypereutectic and hypoeutectic composition cooled from above the liquidus and from a temperature between the liquidus and the eutectic temperature. Primary phase a was concluded to be an efficient nucleant for the other phase B, if the following experimental result was obtained. Referring to Fig. 1, the temperature TI at which a drop of hypereutectic alloy of composition B froze when cooled from above the B liquidus was noted. This was the nucleation temperature for B in the absence of a. A drop of hypoeutectic alloy of composition A was then frozen from temperature T2 between the a liquidus and the eutectic temperature. The temperature T3 at which the eutectic nucleated in the presence of the primary or proeutec-tic a was noted. If this temperature T3 was higher than the temperature TI at which the B nucleated in a hypereutectic alloy, it was concluded that the primary a had nucleated the 6. This temperature T3, representing a certain undercooling below the equilibrium eutectic temperature Te , was designated ?TB by a> the undercooling below T, for nucleation of 13 by a. If there was no substantial difference in nucleation temperature between the hypereutectic drop cooled from above the /3 liquidus and the hypo-eutectic drop cooled from a temperature between the a liquidus and the eutectic temperature, it was considered that the a nucleated B at an undercooling equal to or greater than that at which P nucleated from a hypereutectic alloy. Sundquist and Mondolfo1 found that faceted primary crystals were good nucle-ants for metals that grow as orthogonal dendrites when present as the primary phase. Jackson2 has questioned Sundquist and Mondolfo's technique and proposed that in Sundquist and Mon-dolfo's samples, such as composition A, primary a retained B in reentrant grooves at their surfaces when heated to a temperature above the eutectic but below the a liquidus. This objection was suggested by experiments with organic eutectics where reten-

Jan 1, 1970

By K. L. Moazed, G. M. Pound

An investigation was made of the deposition of silver from a thermal beam onto tungsten field-emitter tips at 300°K. "Island"-type nuclei were observed to form and grow. The nucleation of silver crystals occurs preferentially on non-close -packed planes of a tungsten tip at a critical volume free-energy change of about —2900 cal per cc. The adatom population which is critical for appreciable nucleation rate of silver crystals is about 0.2 of a monolayer and is essentially independent of beam flux, time, and source temperature. This result is strong evidence that a metastable equilibrium exists between adatoms and critical nuclei, as assumed in the present theory. SOME of the more significant studies of nucleation in deposition of metals from vapor beams have been conducted by measuring the thermal beam flux which is critical for appreciable rate of nucleation on a substrate surface held at a given temperature.'2 The observed critical supersaturations may be described in terms of Eq. [7] which was derived3'3a on the model of an adsorption, surface migration, and statistical fluctuation mechanism. However there usually made with a low-power optical microscope, a fairly insensitive method of detection. The object of the present study was to overcome some of these difficulties by measuring the critical supersaturation for condensation of a thermal beam of silver onto a tungsten field-emitter tip. Such a tip may be cleaned by electrically heating it to a high temperature in situ, and the high vacuum obtainable in a field-emission tube (10-10 torr) precludes adsorption of residual gases for convenient periods of time. Furthermore, the degree of cleanliness, the orientation, and the state of imperfection of the tip may be ascertained from the field-emission pattern. Detailed explanations of theoretical considerations and experimental procedures relating to the field-emission microscope may be found in a number of excellent review articles12'13 and thus only a brief description will be given here. The electronic work function of a metal is defined as the energy that an electron needs to escape from the potential field of the solid. By applying a large field between the surface of the solid and a suitable collector, it is possible to free the electrons by the tunnel effect. Fields of approximately 30 million v per cm are needed to produce this effect, and such fields are obtained in practice by using microscopic surfaces of high curvature (tips). Because the work function of a metal is a function of surface orientation, the emission from the various planes is different, and thus it is possible to obtain a representation of the surface in the emission microscope. In general, the work function is higher for the more densely packed planes. Fig. 1 shows a pattern for "clean" tungsten in which the central dark region represents the (110)

Jan 1, 1964

By J. K. Edgar

For a number of years the production and use of super-purity aluminum (better than 99.99 pct) has been steadily increasing. High-grade lots of. such aluminum show certain outstanding characteristics not found in lower grades containing principally silicon, iron and copper as impurities. One such characteristic is the so-called "self annealing," that is, the re-crystallization of the heavily cold worked metal at room temperature.' Interest therefore is aroused as to the effects of the impurities. It is well known that the amounts of silicon and copper which occur in aluminum of better than 99.95 pct are completely soluble, at least at elevated temperatures (above 200°C). Iron, on the other hand, is known to be fairly insoluble in solid aluminum. Thus, a knowledge of the limits of this solubility would he of considerable use in studying the characteristics of the high purity metal. All investigators have agreed that iron has very low solubility in solid aluminum. Rosenhain, Archbutt and Hanson2 reported traces of an aluminum-iron phase in the "purest samples of aluminum obtainable." Gwyer and Phillips3 reported that an iron constituent was visible under the microscope in metal containing ".0088 per cent iron." Roth4 found that in the solid state the solubility of iron in high purity aluminum was 0.01, 0.01, 0.017 and 0.022 pct at 225, 320, 500 and 600°C respectively. Dix5 working with alloys containing less than 0.03 pct impurities, concluded from microscopic and chemical analyses of eutectic areas that the eutectic composition was close to 1.7 pct iron. Dix placed the eutectic temperature at 65s°C. Archer and Fink,6 using high purity aluminum-iron alloys, found that the hypoeutectic liquidus intersects the eutec-tic horizontal at 1.7 pct. This is in fair agreement with the investigation of the aluminum-iron system by Gwyer and Phillips who placed the eutectic at 1.89 pct iron with a freezing point of 653'C. Preparation and Chemical Analysis oP Alloys Electrolytically refined aluminum (99.991 pct aluminum) and a high purity alumi-num-iron alloy (11.45 Pet iron) were used in the preparation of the alloys for this investigation. To aid in controlling the iron content of the experimental alloys, an alloy of lower iron content was prepared first from these materials. The high purity aluminum was melted and heated to about 700°C in a plumbago crucible coated with alundum cement and the aluminum-iron alloy was then added. The alloy was thoroughly stirred, fluxed and skimmed and then chill-cast into notch bars. The aIlalyses of the three materials are given in Table I. The alloys for the determination of the solid solubility of iron in aluminum were prepared by melting 600 g total of the aluminum plus the required quantity of the aluminum-iron alloy (No. 92531). These

Jan 1, 1949

By H. S. Cannon, F. N. Rhines

The application of a static load to a copper powder compact during sintering at an elevated temperature accelerates the rate of sintering in such a way that a given load induces the same proportional increase in rate for all times of sintering. It is shown that sintering under a load is like creep under a fixed load in that the stress required to accomplish a given degree of densification is proportional to the logarithm of the sintering time. VIRTUALLY all of the theories of sintering that have been put forward within recent years have contained the assumption that the chief driving force of the process is the surface tension resident in the exposed surfaces and internal pores of the compact, or powder mass. An externally applied load might be expected to provide a somewhat equivalent driving force for sintering. It is known that the application of a compressive load, during sintering, hastens densification, but it is by no means clear whether sintering under the influence of surface tension alone and sintering under an applied load are fundamentally similar processes. The present study was undertaken in an effort to obtain an answer to this question and with the hope that the answer may contribute to an understanding of the mechanism of sintering. It has been found that there is a close relationship between sintering and creep processes. Copper powder compacts were sintered in hydrogen at 1000 °C under dead loads of 0 to 165 psi and the progress of sintering was observed by means of density measurements. Using a commercial reduced oxide copper powder, see Table I, cylindrical compacts Yz in. x x in. high were made at a pressure of 12,500 psi. For sintering, these were placed in a cylindrical graphite container into which they fitted snugly. A compressive axial load was applied to the compact through a graphite rod of similar diameter, which rested upon the upper end face of the compact; iron weights, in suitable amount, were placed upon the graphite rod to provide the load. This assembly was encased in a vertical silica tube within a resistance-type furnace capable of maintaining a substantially constant temperature within the working zone. After various predetermined times at temperature, the samples were removed from the furnace and their density was measured by conventional means. The heating-up and cooling-down times have been included in the computed sintering time, using the assumption that the sintering rate doubles for each increase of 10 °C in temperature. The experimental results are presented in Table 11. Upon metallographic examination of the specimens, it was found that there was no apparent change in the shape of the pores as a result of loading, i.e, no flattening, Fig. 1. Substantial contraction away from the container walls was observed in all samples sintered with loads of 10.5 psi and less.

Jan 1, 1952

By J. G. Benford, E. B. Stanley

THERE have been numerous papers in the literature1 on the subjects of secondary and tertiary recrystalli-zation in silicon steels. Secondary re crystallization is believed to occur in silicon steel by either a surface-energy phenomenon such as in the usual development of cube texture or by a second-phase phenomenon such as in the usual production of cube-on-edge texture, (110)[001]. Tertiary recrystallization in silicon steel is thought to be a surface-energy phenomenon in which, for example, grains having a (110) plane parallel to the sheet grow at the expense of other grains in the matrix including those having a (100) plane parallel to the plane of the sheet. In all these instances, the orientations involve either a preferred (100) or (110) plane in the plane of the sheet. Until very recently, there had been no experimental evidence reported of the occurrence of a texture by secondary or tertiary recrystallization that involves a (111) plane in the plane of the sheet, although Kohler reported that grains having the (111) plane parallel to the sheet surface can also grow by a surface energy mechanism. Stickels observed a secondary texture in iron described as "near {554}(225)" about 5 deg from {lll}(211).3 Mee reported that in a vacuum-remelted commercial 3 pct Si steel {lll}(hkl) secondary recrystallization took place in a high vacuum and in pure hydrogen.4 Recently in our Laboratory, large-grained structures such as shown in Fig. 1 having an orientation near (111)[211] or (111)[2ii] have been observed. The arrows point to areas of relatively small matrix grains of the kind that the much larger (111) grains consumed while growing. It is of interest that the matrix grains of samples annealed at 2000°F were essentially the same size as those in samples annealed at 2200°F, a matrix-grain-size stability that is characteristic of secondary recrystallization processes. A torque disc taken from Grain 4 of the sample shown in Fig. 1 revealed a very flat magnetic-torque curve, as expected, with a maximum torque of 7000 dyne-cm per cu cm compared to the typical 180,000 dyne-cm per cu cm observed for conventional (110)[001] textured material. A back-reflection Laue pattern for Grain 4 is shown in Fig. 2 and indicates a near-perfect (111)[211] orientation. The other six numbered grains in the sample of Fig. 1 had a similar orientation. The small circles next to each number were the target areas for the X-ray beam. The starting material was an 0.011-in.-thick oriented silicon steel, (110)[001] texture, containing 3 pct Si. It was lightly pickled, cold-rolled to 0.005 in., and annealed 4 hr at 2200°F within a nickel box (not gas-tight) inside a tube furnace through which dry hydrogen was flowing. The samples were heated to 1500°F in 1 hr and then at 60°F per hr to 2200°F. There were other

Jan 1, 1969

By L. D. Jaffe, D. C. Buffum, F. L. Carr, M. Goldman

IN an earlier investigation by Jaffe and Buffum,' a time-temperature transformation diagram for isothermal temper embrittlement of an SAE 3140 steel showed some suggestion of two overlapping "noses." These authors mentioned, as a possible explanation, that their specimens embrittled at 525°C were slightly softer than expected, perhaps because of some slight unknown variation in tempering treatment. Because a double nose would be of considerable importance in elucidating the mechanism of the temper brittleness reaction,' it appeared worthwhile to redetermine the portion of the diagram near 525°C. The same heat of SAE 3140 steel was used as in the previous work, and experimental procedures were the same.' Blanks were austenitized 1 hr at 900°C, water-quenched, tempered 1 hr at 675°C, and water-quenched. Groups were then embrittled isothermally at the temperatures and for the times shown in Table I, and water-quenched. For comparison, one series was tempered various times at 675°C, water-quenched, and given no further treatment. V-notched Charpy impact specimens machined from the blanks were tested over a range of temperatures. Energy absorption and percentage of fibrous fracture were plotted vs test temperature for each group, utilizing both the new data and those for the same treatment obtained in the earlier work,' except that the earlier data at 525°C were discarded.* are given in Table I. After a small correction (-0.28°C/BHN) for the variation of hardness" from Rockwell C24, the transition temperatures were plotted against embrittling time for each embrittling temperature, using the data of Table I for the range of treatments covered there, and using previous dataL for other treatments. By cross-plotting, Fig. 1 was finally obtained. It appears from this figure that if there are two noses to the time-temperature-transformation diagram for isothermal temper embrittlement of SAE 3140 steel, the upper nose must lie above 575°C. As interest had been primarily in the region near 525°C, a thorough study of embrittlement above 575°C was not made. Fig. 1 shows that such a study is needed, especially since preliminary measurements at the tempering temperature of 675°C reveal much more rapid embrittlement than would be expected from the data at lower temperatures. The transition temperature increased, approximately, as the logarithm of the tempering time (about 81/2°C, after correction for hardness, for each doubling of the time).& Since three tensile specimens tempered 240 hr at 675°C and water-quenched had an average yield-tensile ratio of 0.844, with 70.7 pct reduction of area, it is assumed1 that the tempering temperature is not above Ae1. The omission of a quench-and-reheat operation below Ae1, for the groups tempered at 675°C, as compared to groups embrittled at lower temperatures, should not affect results." More detailed investigation of embrittlement above 575°C is now under way.

Jan 1, 1954

By John M. Sharp

John M. Sharp, Jr. (Assistant Professor of Geology, University of Missouri, Columbia, Mo.)-Geothermal gradient and surface temperature data anomalies are potentially useful tools in mineral exploration, These data, however, may reflect a number of geologic and hydrologic processes as well as the thermophysical properties of the geologic materials. The author presents a relatively simple model which may be of value in mineral exploration. The lack of consideration of other processes, however, limits its usefulness. For instance, because of erosion or sediment deposition over geologic time the land surface must be considered a moving boundary in such a model. Evaluation of this effect coupled with annual surface temperature and thermal conductivity variations can result in temperature profiles such as shown in [Figs. 4 to 7]. These effects and others, such as ground-water movement," must be considered and filtered from the data before proper interpretation is possible. Another assumption which should have been discussed is, why were the observed mean surface temperatures not used for extrapolation of the gradients in [Figs. 4, 6, and 7?] Conductive heat transport responds to the actual boundary (land surface) temperature, not to theoretical temperatures in the absence of perturbations. Benfield presents a theoretical model for calculating perturbations in the geothermal gradient for erosion and sedimentation. The temperature (T) at any time (t) and any depth below the surface (x) is given by [ ] where T is the mean surface temperature, G, the geothermal gradient, v, the rate of erosion (or sedimentation),[ ], the long-term rate of change of T0, and k is the thermal diffusivity of the rock. Using the author's values and a rate of erosion of 1.54 cm per yr for a period of 10,000 yr, a thermal profile as shown in [Fig. 10] will be generated. A thermal diffusivity of 0.0164 sq cm per sec was used, corresponding to a thermal conductivity of 0.0082 cal per cm per sec per C. In [Fig. 11], a sediment deposition rate of 3.0 cm per yr for a period of 1000 yr was used to generate the subsurface temperature profile. A surface temperature of 24.3°C was used, as specified in [Fig. 9, 7], was set equal to zero for both cases. Superposition on the generated profiles in [Figs. 10 and 11] of the annual surface temperature variation perturbation (which may be calculated in a number of ways) will yield profiles similar to those in [Figs. 4 and 7]. Similar profiles can also be produced by regional ground-water flow. Models like the author's can be of value in mineral exploration. Other processes, however, which affect surface temperatures and gradients must first be considered, calculated, and filtered from the data if anything but the crudest qualitative interpretation is to be made. Robert C. Edmiston (Author's reply)-Professor Sharp has raised three objections to my interpretation of the subsurface temperature data I collected at Silver Bell. These are: 1) No correction was made for erosion or sedimentation,

Jan 1, 1977

By J. M. Snook, F. C. Langenberg

FOR a better understanding of the melting and refining processes, the oxygen content of the steel bath should be determined. The oxygen content influences many process and product variables such as the efficiency of alloy recoveries, the ingot structure (through reaction with carbon in the steel), certain reaction rates, cleanliness (formation of indigenous oxide inclusions), and mechanical properties. Many methods of sampling liquid steel for oxygen have been devised. These methods can be divided into two main groups: 1) taking samples directly in the furnace or ladle;'-'0 2) removing the metal from the furnace or ladle in a sampling spoon and pouring it into a mold, or drawing the metal from the spoon into a sample holder.11-l4 The advantages and disadvantages of the two general sampling methods are presented in Table I. The bomb-sampling technique described by Huff, Bailey, and Richards8 has been used by the Crucible Steel Co. in certain research projects where oxygen contents were needed. It was recognized that a localized boiling condition could result when the mold is introduced into the steel bath, although the work of Gilbert and Bailey9 seems to indicate that the carbon boil occurring in the bomb-sampler cavity has a negligible effect on the oxygen content. In order to confirm the reported negligible effect of a carbon boil, additional work was done with adaptations of the conventional bomb sampler. The methods used are shown in Fig. 1 and are as follows: 1) Type A: aluminum wire (0.125-in. diam) coil in cavity; steel cap over mouth 2) Type B: aluminum cup in cavity; aluminum cap over mouth, 3) Type C: aluminum cup in cavity; steel cap over mouth, 4) Type D: fine aluminum wire (0.013-in. diam) in cavity; steel cap over mouth. The amount of aluminum wire in the Type A and D samples varied from 0.8 to 1.2 pct of the sample weight. The aluminum cups averaged 2.0 pct of the sample weight; the latter were used to ensure that the steel contacting the walls of the bomb cavity was fully killed. Samples were taken from plain carbon heats made in open-hearth furnaces. This grade of steel before silicon additions is essentially an Fe-C alloy and the effects of other alloying elements on the oxygen activity can be neglected. The results of sampling with the bomb samplers is shown in Fig. 2 where the percent oxygen is plotted against the percent carbon on log-log paper. Spoon sample results on the same grade of steel where the sample was killed in the spoon are shown in Fig. 3. The oxygen contents were determined by the vacuum fusion method. A comparison of Figs. 2 and 3 shows that the oxygen concentrations obtained with the spoon-sampling method (metal killed in the spoon after slag removed

Jan 1, 1960

By C. E. Birchenall, M. H. Davis

The rate of oxidation of titanium in the temperature range 650° to 950°C has been measured. 'The linear rate law obtained is explained by interface reaction control of the process. Tracer experiments indicate the oxygen diffuses in at least one phase of the scale. THE kinetics of oxidation of titanium, principally at low temperatures and under varying oxygen pressures, have been reported.¹,² In the present investigation the rates of oxidation of titanium have been determined by the gravimetric method in the temperature range 650" to 1000°C under 1 atm of oxygen. Some of the scales formed were powdered and an endeavor was made to identify the phases present by X-ray diffraction. Alexander and Pigeon1 ascribe a logarithmic rate law to the growth of thick films formed at temperatures up to 565"C, and Gulbransen and Andrew' suggest that the parabolic rate law holds up to 600°C. In both cases large initial deviations from those relationships are apparent and no explanation is offered. In the present experiments it is shown that a linear rate law holds in the temperature range 650" to 1000°C, and it is suggested that the initial deviations observed are due in part to a spurious surface area effect and also to the high solubility of oxygen in titanium metal. Positive information on the mechanism of oxidation is not available, but oxygen ion diffusion through the lattice is inferred from the re- sults of trace experiments. X-ray analysis of the scale confirms Gulbransen and Hickman's' observation on the presence of rutile TiO². Experimental Details The titanium used in these experiments was prepared by the reduction of titanium tetrachloride with magnesium and was used in the form of rolled sheet. Samples approximately 0.040x0.5x0.75 in. were cut and polished to a fineness of 4/0 on metal-lographic polishing papers. Individual samples, suspended on a platinum wire, were lowered into the hot zone of a furnace, in vacuo, by means of a winch, and oxygen was admitted after the desired temperature was attained. The increase of weight of single samples oxidized for fixed times at certain temperatures was determined by weighing the sample before and after oxidation on a chemical balance. In these instances the sample was used for only one time at one temperature. In some cases the course of oxidation was followed by attaching the sample to a sensitive spring balance and noting periodically the extension of the spring with time of oxidation. Kirkendall type experiments were carried out by marking the surface of the titanium prior to oxidation with a solution containing radioactive silver. After drying, the specimen was heated in vacuo to decompose the silver nitrate used, leaving a small amount of metallic radioactive silver on the surface. Following oxidation, these samples were mounted, ground, and then placed in intimate contact with

Jan 1, 1952

By H. C. Chao, Y. E. Smith, L. H. Van Vlack

ThE phase relationships for the MnO-MnS system have been investigated only in the eutectic region. wentrupl reported a eutectic at 1280°C (2345°F) with approximately 50 wt pct of each component, as based on the earlier work of Andrew, Maddocks, and Fowler.2 More recently silverman3 corrected these figures to 2275° ±10°F (1246°C) with 63 wt pct MnS and 37 pct MnO. Neither Wentrup nor Silverman investigated the solid-solution limits in this system. However, Wentrup did suggest with his phase diagram sketch that the maximum solubility of MnS in MnO is 10 wt pct, and the solubility of MnO in MnS is nearer 20 wt pct, Fig. 1. These figures have been utilized in subsequent publications without further verification.4 There had been evidence found in this laboratory that the above solid-solution figures were high. An investigation was therefore conducted using the following procedure. Samples containing MnO and MnS were contained in platinum foil, heated just above the eutectic temperature in a purified nitrogen at- mosphere, and quenched into distilled water. The MnO had been prepared by calcining reagent grade MnCO3 in nitrogen at 1400°C. Only MnO was detected in subsequent X-ray diffraction analyses. The MnS had been prepared by sulfur deoxidation of reagent grade MnSO4 according to the reaction: MnSO4 + S2 ? MnS + 2SO2 The details of the sulfide preparation procedure, which utilized atmospheric sulfur pressures at 950°C, are discussed elsewhere.5 The sulfur content of the sulfide was determined to be 36.8 * 0.2 pct, which matches the stoichiometric value of 36.9 pct. No evidence of either MnO or MnSO4 was detected microscopically or by X-ray diffraction. The single-phase combinations of MnO and MnS at the eutectic temperature indicate the limit of solid solution as shown in Fig. 2(a) and (c), and the revised phase diagram is shown in Fig. 2(d). The melting temperature for MnO is that provided by Glasser.6 The eutectic temperature of 1232° ± 5°C and eutectic composition of 64 wt pct MnS are in close agreement with Silverman's correction of Wentrup's work. The maximum solubility of MnO in MnS was determined to be 1.7 ± 0.2 wt pct. The maximum solubility of MnS in MnO was determined to be 1.8 ± 0.2 wt pct. These figures represent the lower limit for the presence of liquid at 1260°C and are significantly lower than the earlier estimated solid-solution figures. The authors wish to acknowledge the support of U.S. Steel's Edgar C. Bain Laboratory for Fundamental Research. The comments and critical suggestions of Drs. A. S. Keh, R. Rickett, and R. B. Snow are appreciated.

Jan 1, 1963

By B. L. Averbach, M. Cohen, G. P. Conard

IT has been frequently observed that, when metal crystals are bent and annealed or when they are bent at elevated temperatures, the asterism of the Laue spots is split discontinuously into tiny intensity maxima. This finding indicates that segmented crystallites or subgrains are produced, which are relatively undistorted within themselves but which differ slightly in orientation from their neighbors. The following viewpoints have been put forward concerning the nature of this segmentation process: 1—Crussard' has described the phenomenon as "re-crystallization in situ." According to this mechanism, the deformed lattice recrystallizes on heating into an aggregate of comparatively strain-free subgrains separated from one another by low-angle boundaries and having nearly the same orientation as the original crystal. This process differs from the classical type of recrystallization in that the latter involves the formation of grains having quite different orientations from that of the mother crystal. 2—A similar but more detailed picture has been advanced by Cahn' who adopted the term "polygonization." In this interpretation, the plastic bending of lattice planes results in an excess of dislocations of one sign, but at suitable temperatures these dislocations migrate along slip planes and collect in localized regions to form an array of low-angle boundaries. Concurrently, the lattice segments between the boundaries lose their curvature and elastic strain. 3—The "cell formation" concept of Wood and co-workers: unlike the two hypotheses cited, postulates that the segmentation of the lattice is basically a mode of deformation and is not an annealing phenomenon. Cell formation appears to compete more effectively with respect to the normal slip process as the deformation temperature is increased and as the strain rate is decreased. The present work was performed on 3.2 mm diameter 99.99' pct Zn single crystals, grown from the melt in a gradient furnace. The major impurity was 0.003 pct Fe. The crystal orientations ranged from those with basal plane parallel to the rod axis to those with the basal plane almost perpendicular to the rod axis. The specimens were bent on templates to effective radii varying from 14.2 to 1.3 cm at the temperatures from —196" to 100°C. In each case, the axis of bending was parallel to the basal plane. Subsequent annealing was carried out at temperatures from —196" to 400°C. Back-reflection Laue pictures were taken on the convex surface of the bent specimens, before and after annealing. This procedure was found to yield better resolution of the detail in the diffraction spots than did the previously used Laue transmission technique. Some X-ray pictures of rods bent at —196" and —78°C were taken at these respective temperatures without intermediate warming to room temperature. In addition, bent crystals were acid cut" parallel to the basal plane, and double-crystal spectrometer rocking-curves were obtained from the etched (0001) face before and after increment an-

Jan 1, 1954

By Walter Miller

Crude oil stocks were some 10,000,000 bbl higher on June I, 1947, than at any time during 1946 but the extremely heavy refinery runs the last half of 1947 cut crude inventories to approximately the 1946 closing level of 225,000,000 bbl. Many refiners were seriously short of crude oil during the year. This shortage was reflected in numerous advances in the posted price of crude, justified in part as an incentive for more production but more generally due to competitive bidding. Some purchasers of crude, endeavoring to keep their plants running, resorted to the payment, either directly or indirectly, of premiums above the posted price. Another common practice employed by some suppliers of crude oil was to demand refined products in exchange or trade for their raw material. The refined products picture has darkened in spite of record throughputs. Stocks of gasoline and light and heavy fuel oils were uncomfortably low at the beginning of the year and were in general still lower at the close. The rationing of some products, principally gasoline, to dealers and stations? initiated during the year, gained momentum as stocks continued to diminish. The emphasis placed by the manufacturers of oil-burning equipment on the convenience and economy of heating with oil, together with the tight situation in coal, has developed a tremendous demand for burning oils. Consumption of liquefied petroleum gas for domestic and household fuel had more than doubled in 1946 over 1943, and the demand seems to be limited only by the ability of the equipment builders to furnish necessary storage. transportation, and burning equipment. The supply situation is likely to become more acute in 1948. Demand for petroleum products is being pushed to new heights not only by the unprecedented domestic market but by a sudden and drastic upswing in estimates of military and governmental requirements. Additionally, oil exports are running far below the volume requested, amounting to less than forty percent in a recent quarter, and export licenses are reportedly being approved on the basis of urgent need *only. AX recent White House release sees little likelihood that estimated requirements of the sixteen nations participating in the proposed Marshall Plan can be met in full over its projected life—1948 to 1951. Present demand dictates maintenance of refinery operations at the highest possible level and the Bureau of Mines has forecast daily average crude runs in 1948 of 5,265,000 bbl. The Economics Advisory Committee of the Interstate Oil Compact Commission recently estimated the 1948 demand for petroleum products at nearly 6 pct above 1947. They further estimate daily average crude runs of 5,375,000 bbl in 1948, some 2 pct higher than forecast by the Bureau of Mines. Projected demand exceeds supply to the extent that Capitol Hill is reportedly investigating ways of enabling oil companies to act in concert without danger of antitrust prosecution, such as elimination of crosshauls, pooling of products, and lowering of octane.

Jan 1, 1948

By J. H. Frye, J. W. Caum

ONE of the most important methods of increasing the hardness of metals is alloying. In spite of the widespread use of alloys, the fundamental mechanism of alloy hardening is little understood. This is true even of the simplest form of alloy, the primary substitutional solid solution in which solute atoms substitute for solvent atoms at random in the crystal lattice of the latter. A fundamental understanding of the mechanism of solid-solution hardening would be important, both because of the widespread use of alloys of this type and because of the light that might be thrown on the mechanism of hardening in more complicated alloys. The present investigation covers the hardness of primary substitutional solid solutions of zinc, gallium,, germanium; and arsenic in copper. All of these are B subgroup elements from the third period of the periodic table. Cu, Zn, Ga, Ge, and As are in groups I, II, III, IV, and V, respectively and lie just to the right of the transition elements. Because of their cost, it is unlikely that Ga-Cu and Ge-Cu solutions will ever be of commercial importance, but the intent of this study has been to discover some of the fundamentals of solid-solution hardening and it has been demonstrated that such a study is far more likely to be fruitful if alloys are made up on the basis of position of the constituent elements in the periodic table than if commercially important alloys are used. Many investigations have. been made of the hardness of substitutional solid solutions, but lack of attention to purity of the metals, infrequent grain-size control, and the use of varying testing techniques have virtually invalidated any comparisons. The purpose of most investigations has been to solve immediate problems and not to solve the primary problem: Why do solid solutions usually have a greater hardness than pure metals? PREVIOUS WORK Theories have been advanced to account for the hardness of solid solutions,, but relatively little experimental work has been done. Perhaps the first experimental work of merit was that of Norbury1 on copper alloys. He showed that for several alloys there was a correspondence between the hardness of one atomic per cent solutions and atomic volume of the solutions. More recently Brick, Martin, and Angier2 have investigated the effect of various solute elements on the hardness of copper. They concluded that the hardening effect of these solutes depended "primarily on the difference in atomic volume of solute and solvent or, relatedly, upon the parameter, change of the solvent or the extent of solid solubility." They also observed the effect of these elements on hardness and texture developed by rolling and by annealing of rolled material. Austin3 examined the hardness and response to heat-treatment of various iron solid solutions. Frye and Hume-Rothery4 measured the hardness of a number of silver solid solutions containing approximately

Jan 1, 1943

By M. R. Geer

All the coal lands in Alaska are publicly owned, and the Federal Government is the principal consumer of coal. Therefore the Government has long been concerned with the wise utilization of the coal reserves of Alaska as well as with the availability of coals meeting the specifications for use in various Government installations. Coal preparation plays a key role in both of these areas of interest. The proper choice and operation of coal-washing equipment permits the mining of inferior deposits, minimizes waste of coal in preparation, and assures a prepared product of the best quality obtainable from the raw coal. Thus, from time to time, the Bureau of Mines has made washability examinations on most of the coals mined in Alaska. Generally, these examinations were made when new mines or new beds were opened, when construction of new preparation plants was being considered, or when the operation of existing plants could be improved by better knowledge of the raw coal. The purpose of this report is to bring together all the washability data available on the coals of the Matanuska Valley and Beluga River fields. The pattern of energy development for the rapidly growing Anchorage area is not clear at this time. Formerly coal was the only fuel available for large-scale space heating and power generation. More recently both oil and natural gas have entered the market, and several hydroelectric projects have been completed. Additional major hydroelectric projects are being considered. The role that will be played by coal in this competitive energy market is uncertain. However I if coal is the fuel used in future power plants or industrial installations, the information contained in this report will be useful in indicating the quality of the coals that can be supplied and in selecting proper preparation techniques.

Jan 1, 1962

By William Fink

THE constitution of the aluminum-cobalt alloys has been the subject of relatively few investigations. Brunck1 analyzed the residue which remained after treating the 17 per cent cobalt alloy with dilute hydrochloric acid. The results of the analyses indicated the existence of a compound Co3Al13. Guillet2 published a liquidus for the aluminum-cobalt system which contained two maxima corresponding to CoAl6 and CoAl2 and two eutectic points at 30 and 74 per cent Co. The most extensive investigation of the system was carried out by Gwyer,3 whose results are summarized in Fig. 1. It will be noted that at the aluminum end there is a suppressed eutectic at 644° C. By extrapolation of the duration of the eutectic arrest to zero, the composition of the compound was placed at Co3Al13. Another thermal arrest was noted at 550° C., which Gwyer attributed to a peritectic reaction. The present investigation of the aluminum end of the aluminum-cobalt system is the eleventh of a series dealing with the constitution of aluminum; rich alloys prepared from electrolytically refined aluminum.4 Preparation of Alloys.-The alloys used in this work were all prepared from electrolytically refined aluminum, the analysis of which is shown in Table 1. In preparing some of the alloys, metallic cobalt (98 to 99 per cent) was used either directly or in the form of an intermediate alloy, the composition of which is given in Table 1. In order to obtain alloys of higher purity, cobalt was introduced into some of the alloys by means of chemically pure cobaltous chloride which was readily reduced by the aluminum. A small electric furnace with nickel-chromium heating elements was used in the preparation of the alloys.

Jan 1, 1932