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By O. N. Carlson, S. A. Bradford

Discontinuous yielding in tensile tests was observed in V-O alloys in the temperature ranges of 150° to 175°C and also 350° to 400°C. The magnitude and intensity of the serrations were found to vary considerably with oxygen content. Maxima were observed in tensile and yield strengths and in the strain-hardening coefficient at the higher temperature only. The strain rate sensitivity was observed to be negative between 150° and 400°C. THIS investigation was undertaken to study the effect of oxygen on the tensile properties of iodide vanadium in the temperature range of 25o to 450°C. Brown1 observed an increase in strength between room temperature and 400°C in vanadium metal, and found that oxygen and nitrogen had a rather pronounced effect on the strength and ductility. A maximum in the tensile strength was observed by Rostoker et al.2 near 300oC and by Pugh3 around 450°C for calcium-reduced vanadium. Pugh also found a maximum in the yield strength and in the strain-hardening exponent, and minima in the elongation and strain rate sensitivity at the same temperature. Eustice and Carlson4 reported the appearance of serrations in the stress-strain curves between 140° and 180°C in iodide vanadium containing 600 ppm O. These anomalies in the mechanical properties indicate that strain aging occurs in vanadium, but the impurity or impurities responsible for the above-mentioned effects have not been identified. The phenomenon of strain aging is usually characterized by the return of the yield point after interruption of a strength test. In the temperature range where strain aging occurs, the yield and tensile strengths attain maximum values, elongation and strain rate sensitivity exhibit minima, and discontinuous yielding is generally observed in the stress-strain curve. Cottrell5, 6 has postulated that strain aging is due to the migration of solute atoms to dislocation sites to produce locking after the dislocations have broken free from their impurity atmospheres during the initial yielding. At the strain-aging temperature the process is a dynamic one in which the solute impurity atoms diffuse to the vicinity of the moving disloca- tion producing "locking" which gives rise to maxima in the tensile strength and serrations in the elongation curves. Cottrel17 has noted that discontinuous yielding in iron occurs when the diffusion coefficient of nitrogen, D, and the strain rate, i, are related by D = 10-9 €. EXPERTMENTAL PROCEDURE The vanadium metal employed in this study was prepared by the iodide refining process as described by Carlson and owen.8 A representative analysis of the vanadium used in this investigation was: 150 ppm O, <5 ppm N, <1 ppm H, 150 ppm C, 150 ppm Fe, 70 ppm Cr, <50 ppm Si, 30ppm Cu, 20 ppm Ni, <20 ppm Ca, <20 ppm Mg and <20 ppm Ti. Alloys containing from 200 to 1800 ppm O, all of which lie in the solid solution range of the V-O system, were prepared by arc melting vanadium together with portions of a high-oxygen master alloy. The master alloy was prepared by tamping pure V2O5 into holes drilled in a vanadium ingot and arc melting this five or six times in an inert gas atmosphere, inverting the button between each melting step. The oxygen content of the master alloy was then determined by vacuum fusion analysis. Vanadium containing less than 150 ppm O was prepared in the following manner. A bar of iodide vanadium was deoxidized by sealing it in a tantalum crucible with a few grams of high-purity calcium. This was held at 1100°C for 4 days to allow time for the oxygen to diffuse to the surface and to react with the calcium vapors. The calcium oxide product was later dissolved from the surface of the bar with dilute acetic acid. In this way vanadium containing from 20 to 50 ppm O was prepared. Sample Preparation. The are-melted ingots were cold swaged into 3/16-in. diam rods and these were machined into cylindrical tensile specimens with a reduced section of 1.00-in. length and 0.120-in. diam. The test specimens were annealed for 4 hr at 900°C in a dynamic vacuum of mm of Hg to remove hydrogen from the metal. This recrystal-lization treatment produced a uniformly fine-grained structure with a mean grain size of approximately 0.06-mm diam. The oxygen contents reported in this paper were determined by a vacuum fusion analysis of the tensile specimens after testing. Analyses for other interstitial or metallic impurities showed no significant changes from that of the original material. Tension Tests. Tension tests were performed on a screw-driven tensile machine at a constant cross-head speed of 0.01 in. per min. Tests at elevated temperatures were carried out by heating the

Jan 1, 1962

By B. Fitch

This paper deals with the behavior of sedimenting suspensions. More particularly, it treats, in as organized a manner as possible, the body of knowledge, theoretical or empirical, by which one predicts the behavior of miscellaneous swarms of particles in suspension. Such knowledge is necessary for precise and economical design of equipment. While the behavior of a single spherical particle settling through an infinite sea of quiescent fluid is well understood, practical sedimentation processes are almost always concerned with particles of assorted sizes, densities, and shapes, in such concentration that there is profound particle interaction. Such swarms of particles are observed to settle in any of four markedly different manners. Which one they follow is governed by particle interaction. It is determined largely by the dilution of the suspension, and the relative tendency of the particles to cohere. TYPES OF SEDIMENTATION The relationship between the different modes of sedimentation is shown paragenetically in Fig. 1. The left side of the diagram represents particles having little tendency to cohere; the right side represents particles for which interparticle cohesion is large compared to the settling force. The vertical axis represents dilution. As seen in the diagram, sedimentation is divided into three broad fields or regimes. At high dilutions there exists a regime here named &apos;clarification.&apos; Particles in clarification may settle either individually, or by collecting into separated floccules. Thus there are two different possible modes of settling in the clarification regime. It is characteristic c~f this regime that there will be no clear line of demarcation between settling suspension and a supernatant. Faster particles settle out ahead of slower ones. In batch tests there develops a gradation of both particle sizes and pulp density due to progressive depletion of the largest particles from any given pulp level.

Jan 1, 1962

By Robin O. Williams

The textures which are produced by simple shear in poly crystalline samples of copper, brass, aluminum, iron, and zirconium have been determined. For the fcc materials, there are two major textures, both of which are oriented for slip on the usual slip systems. It is shown that each grain will, in general, give rise to both orientations through the production of deformation bands. This is considered a clear demonstration that such bands aye produced by the heterogeneous deformation which takes place instead of the five-slip-system model considered by Taylor. The results on iron and zirconium are more limited but would appear to exhibit certain additional complexities. It is suspected, however, that the general consideration of deformation bands may apply here also. One finds some correlation between the textures produced by this single shear and the conventional textures although it would appear- that additional data and analysis are requived to produce a strong correlation. It is somewhat remarkable that of all the texture investigations only a very few have been concerned with the action of simple shear on polycrystalline aggregates. Of these limited investigations, all used torsional strains and only in Backofen&apos;s&apos; and Backofen and Hundy&apos;s "ork was sampling carried out so as to derive a texture in terms of the shear direction. Some rather remarkable conclusions re- sulted from Backofens&apos;1,2work: 1) the rate of texture formation in copper is high, being almost complete at a shear strain of unity; 2) the texture does not change if the sample is sheared back, although the surface grains return to their original shape; and 3) the texture is complex in that it has four components, three of which have [110] as a shear direction. These conclusions were based on both qualitative and quantitative data. Shear deformation is intermediate in complexity between simple shear of single crystals and the usual deformation of polycrystals; hence, one might expect to learn considerable from the extension of this work. CONVENTION Deformation in simple shear has the lowest possible symmetr3, less than the other simple modes of deformation (rolling, drawing, and compression); hence, one cannot necessarily expect the textures to have the same degree of symmetry. The geometry of the process is represented by Fig. 1 along with its sltereographic projection. One has the shear plane, the shear direction, the mirror plane normal to the shear plane and containing the shear direction, and a neutral plane normal to both the shear plane and mirror plane. These planes divide the projection into four quadrants. These quadrants are not, however, identical, since all directions within the upper left and lower right are being shortened by the shear process, and the other directions are being lengthened. The first kind are called compression quadrants and the direction of greatest contraction rate, at 45 deg, is labeled with a minus sign; the corresponding direction of greatest extension rate

Jan 1, 1962

By D. G. Oss, S. E. Erickson

An automatic control method for the ferrosilicon heavy media process maintains media density within 0.01 specific gravity points. Continued demands for higher grade, competitive products from the Mesabi Range have resulted in experimental work such as that detailed for one concentrator. Various methods, step by step procedures and instruments used at an iron ore beneficiation plant in the development of an automatic control system are described. Work continues and it is hoped that further applications of control instrumentation can be made in the next operating season. The need for instrumentation and automatic control of the various parameters in the heavy media process of iron ore beneficiation has been apparent for some time. Continued demands for higher grade, competitive products from the Mesabi Range have made it necessary to increase the efficiency of the process in every possible way. In a typical heavy media flow scheme for iron ore beneficiation (Fig. 1) a sized, prepared feed (generally about —1% in. to +% in.) is fed to a heavy media separatory vessel, along with a ferrosilicon slurry. A separation of the feed is made on the basis of specific gravity. Low density particles overflow a tailings discharge weir, while high density ore particles sink to the bottom of the high density pool and are moved away to the concentrate discharge chute. Both products are passed over drainage screens and then are cleaned thoroughly of attached ferrosilicon on wash screens. Float material is generally stockpiled, while the sink product is shipped as a final concentrate. Undersize from the drain screens is returned directly to the circulating media sump. Wash screen undersize is cleaned of contaminating ore particles and slimes by passing through magnetic separators. Provision is also made for splitting a portion of the tailings drain undersize into the cleaning circuit if necessary for control of depth of tailings overflow, or for additional cleaning as required. Cleaned ferrosilicon is stored in a densifier and returned to the Circulating media sump as make-up material. Dilution water is also added to this sump to maintain a desired specific gravity of the circulating media. As in any process, operational intelligence is secured only by keeping records of the process variables. Generally apeaking, plant operators have neither the inclination nor the time to keep complete and detailed records of these variables over the course of their shift. Before instrumentation was added to aid the operator, specific gravity was measured by weighing a given volume of pulp at intervals of from 30 to 60 min. Scale readings were made at the beginning and end of each shift. No records were kept of operating conditions, such as rpm of the separatory ves-sel, media level in the machine, tons per hour of the products, and so forth. These items were recorded only when spot checks were made by the metallurgical staff. CONTlNlJOUS DENSITY RECORDING The first process instrument used, other than the usual ammeter on the drive motor of the separatory vessel, was a nuclear density gauge and its associated circular chart recorder. These instruments were used to indicate and record specific gravity of the circulating media. This was a tremendous aid to the operator in that tie was able to observe and correct the specific gravity at any time. There was also added incentive to make frequent corrections because of the permanent record made by the recorder of the densities. The addition of the nuclear density gauge was influential in securing optimum quality and recovery of the heavy media product. Manual control was improved, and it became possible for a good operator to main control within f.05 specific gravity units. This compares with an unknown quantity, estimated at f0.15 gravity units, when manual measurement and control was used. An example of the improvement in manual control over the course of one season&apos;s operations is shown in Fig. 2. Chart A is typical of the records made shortly after the gauge was installed. Needless to say, it was difficult for operators and foremen alike

Jan 1, 1962

By R. J. Sherman, M. R. Achter

IT has often been reported that coatings may strengthen single crystals and polycrystalline specimens of coarse grain size. This note reports the effect of a surface layer of fine grains on the creep-rupture properties of coarse grained nickel 99.8 pct pure. Sheet specimens were machined from cold-rolled material, finished by surface grinding and annealed at 1230°C in vacuum for 4 hr. Half of them were re-ground on faces and sides and annealed at 925"C for 1 1/4 hr. The double grind-anneal treatment produced a structure consisting of a surface layer of fine grains of 0.02 mm diam on a coarse-grained substrate of grains of 0.40 mm diam. Comparison with specimens which received only the single grind showed that the second grind-anneal did not alter the structure of the substrate. Several modifications were made in specimen design to eliminate erratic rupture behavior outside of the gage length. In the final design the gage section, oriented parallel to the rolling direction, was 1.00 in. long, 0.4 in. wide, and 0.0625 in. thick. End tabs were pinned in place. Although other configurations (welded end tabs, transverse orientation, and wider gage section) showed similar effects of a layer of fine grains, because of the erratic rupture behavior, only the data from the final design are reported here. Creep tests were performed at 650°C in air and in a vacuum of 10~5 mm Hg. Creep rates were measured from the movements of the lever arm. Since the broken sheet specimens could not be fitted together, elongations at fracture measured by means of gage marks, do not include the necked portions adjacent to the fracture. Results of the creep tests with and without the fine grained surface are given in Table I. An explanation for the lower strength in air than in vacuum has been proposed previously in terms of the reduction of crack propagation energy by gas adsorption.l In both environments the fine-grained layer produced a small decrease in minimum creep rate and, except for the shortest test in air, a substantial increase in rupture life. The elongation values at rupture, as they are measured here, do not demonstrate an appreciable effect of the grain structure but do show much smaller ductilities in air than in vacuum. Greater elongations maybe associated with the finegrained layer, however, especially in vacuum, in creep curves such as those in Fig. 1. Duplicate tests were not run to determine the re-producibility of the data. It is felt, however, that, in view of the consistent behavior, the prolongation of rupture life may be attributed to the effect of the fine-grained surface. In the data not reported be-

Jan 1, 1962

By L. F. Mondolfo

An investigation of the relationship between properties of the elements and type of binary diagram formed was conducted. It was found that, for each type of equilibrium diagram, the factors for the size, valence, electronegativity, period, melting point, entropies of fusion, and sublimation calculated for each pair of elements cover a range of values. However, these factors show sufficient relationship to the equilibrium diagram so that the correlation of several of them can be used to predict the type of diagram formed, or at least limit the choice to only a few types. ThE goal of the metallurgist concerned with alloy development has always been to find a method that predicts the properties that can be obtained when a certain metal is added to another one. In most cases a qualitative predictiton of properties can be made if the equilibrium diagram is known. However, this means that for new metals the alloy development has to start with the experimental determination of the equilibrium diagrams. Because this determination is at least as complicated and time-consuming as the determination of the properties themselves, most alloy development has taken place by trial and error, and the study of the equilibrium diagrams has followed rather than preceded the creation of new alloys. Alloy structures and properties depend on the interaction between electrons and a complete knowledge of these interactions would permit prediction of structure and properties of alloys. Unfortunately direct measurement of these interactions is extremely difficult and somewhat doubtful and only properties that depend on them can be measured easily and with certainty. Study of the relationship between properties of the elements and equilibrium diagrams is not new. Besides the well known Hume-Rothery rule of the necessity of an atomic diameter fit within 15 pct for extensive miscibility in the solid, and the wide knowledge of the effect of such factors as size, electronegativity, electron-atom ratio on solid state features,"&apos; work relating to liquid state and liquid-solid reactions can be found in the literature. Of particular interest is the work by Axon,3 who investigated the effect of size and melting point on a selected number of eutectic and monotectic dia-

Jan 1, 1962

By R. E. Steiner, A. F. Weinberg, R. J. Van Thyne

Uranium solubility in molten bismuth was determined in the temperature range 350" to 600°C, varying from 0.09 wt pct to near 2 wl pct, respectively. Zirconium and magnesium, simulated fission products, and sodium were found to increase or decrease uranium solubility in bismuth in the temperature range 370° to 420°C, depending upon the addition or temperature. Data were obtained by both chemical analysis of samples obtained by filtration from saturated melts and by measurement of the variation of electrical resistance with temperature. IN a study for the United States Atomic Energy Commission, a Liquid Metal Fuel Reactor Experiment (LMFRE) was proposed in which a solution of uranium dissolved in molten bismuth served as both the fuel solution and the primary coolant. It was proven necessary to add other elements to this solution for certain desirable properties: 1) zirconium acts to prevent reaction of the fuel solution with the graphite core (which would result in the formation of uranium carbide) and also to inhibit mass transfer of iron and chromium from the walls of the reactor tubing to cold spots resulting in blockage; and 2) magnesium acts as a deoxidant and prevents loss of uranium. In addition to these intentional additives, other elements entering the solution are: 1) fission products which are a by-productof reactor operation, 2) sodium (the secondary coolant) through possible small leaks in the heat exchange system, and 3) iron and chromium from the container walls. Each of these elements may affect the solubility of uranium in the fuel solution. Since the concept of this reactor is based upon a liquid solution, the relatively low solubility of uranium in bismuth will dictate the minimum temperature at which the reactor heat exchanger can be operated. The solubility of uranium in liquid bismuth and the effect of some additives on this solubility have pre- viously been investigated1-&apos; (more recent results6" became avaliable after initiation of this investigation). However, some discrepancies between the various results have been noted, and also the cumulative effect of the several additions or impurities was not known. This investigation was commenced to obtain definitive results. MATERIALS Analyses of the materials used are presented in Table I. Although ostensibly of extreme purity (99.999 wt pct), the bismuth was found to contain a significant amount of impurities, probably oxides. Except for determination of the binary system, Bi-U, prior to use all bismuth was hydrogen-refined and

Jan 1, 1962

By G. K. Manning, E. R. Stein, E. E. Underwood

Columbium, carbon. and nickel additions were made to iron-base alloys with 20 pct CY. The effects on microstructure, precipitation-hardening characteristics, and High-temperature properties were investigated by means of metallographic, hot-hardness, and magnetic measurements. An austenitic alloy consistilzg of Fe-20Cr-14Ni-0.8C-2.5Cb had higher hot-lzaciness at 1700°F than the other alloys investigated. Its favorable standing is attributed to an enhanced interaction of Cb and Cr4C particles dispersed within a stable austenitic matrix. FOR the past 20 years, cobalt- and nickel-base alloys have been used for the more stringent high-temperature applications because of their excellent creep resistance. Although their performance is quite satisfactory, other base materials must be considered for large tonnage, low-cost applications such as for the automotive gas turbine. Iron-base alloys are also used extensively, but at somewhat lower temperatures, primarily because of the instability of particles or because precipitation occurs at relatively low temperatures. Since unusual stability has been reported for Fe-Cb and Cb-C compounds.1-3 it was hoped that effective amounts of these compounds could be taken into solution at temperatures just below the melting range, then precipitated upon reheating. Actually, strengthening was found to occur by both precipitation hardening in some alloys and by phase transformations in others. Among the alloys investigated, that with the best high-temperature properties owes its strengthening to a combination of carbide particle interaction and a relatively stable austenitic matrix. EXPERIMENTAL PROCEDURES Small preliminary melts of about 100 g were made in a vertical Glotube furnace, using alundum crucibles and an argon atmosphere. Alloys weighing 35 lb were melted in a basic-lined induction furnace, also under argon. The compositions of the alloys are given in Table I. The nickel-free alloys were usually ferritic, while those containing nickel were generally austenitic. Depending upon the particular heat treatments, or the combination of alloying elements, two-phase alloys of ferrite and austenite could be obtained. In the following text, however, the nickel-free or nickel-bearing alloys are referred to simply as either ferritic or austenitic alloys respectively. The small ingots were swaged at 2000°F, in steps, to rods of approximately 3/16-in. diam. The large ingots were forged at 2100°F to 1-in. sq bars. No difficulties were encountered in swaging or forging any of the alloys to as much as 90 pct reduction in area. For heat treating at temperatures above 2000°F, specimens were sealed in quartz tubes under a partial pressure of helium. No special precautions were found to be necessary at lower temperatures. Intermetallic compounds in the preliminary alloys were identified by means of X-ray diffraction measurements. Correlation of these results with micro-structural characteristics (such as color, shape, size, and location) of the compounds aided in their identification. Magnetic susceptibilities were also obtained at room temperature with a Magne Gage instrument after the various heat treatments. To

Jan 1, 1962

By H. I. Aaronson

Isothermally formed plates of proeutectoid a, lengthen at approximately the rates predicted by the Zener-Hillert equation, indicating that their lengthening kinetics are controlled by the volume diffusion of chromium in the ß matrix. Solution annealing treatments in the vicinity of the transus introduce a second mode of transformation, in which the lengthening rate is at least 1.8 x 104 faster than predicted by this equation. Little or no volume diffusion appears to accompany the latter transformation. The Presence of oxygen is evidently a Prerequisite for the occurrence of this reaction. X HE effects of thermal history prior to the initiation of transformations which proceed by nucleation and diffusional growth are currently evoking considerable interest. The rate of nucleation (but not the rates of growth) of pearlitel and of bainite,2 and the over-all rates of aging reactions in Al-cu3 and Al-si4 alloys have been shown to be appreciably dependent upon thermal history in the solid-solution region"&apos; or in the two-phase region prior to the onset of pre~ipitation.3,4 In none of these reactions, however, was the transformation mechanism changed by variations in the temperature-time path used to reach the reaction temperature. Preliminary experiments reported by M. K. McQuillan5,8 and a systematic investigation by Farrar and Margolin7 have disclosed that the transformation behavior of hypoeutectoid Ti-Cr alloys is considerably more sensitive to thermal history. Qualitative evidence strongly suggests that not only the rate of nucleation but also the rate of growth and even the mechanism of the ß — a reaction can undergo remarkable changes when a solution annealing treatment in the vicinity of the ß/a +ß, or transus temperature, is interposed between a high-temperature solution anneal (conventionallq at 1000°C) and the isothermal reaction treatment. The present investigation was undertaken in an attempt to ascertain the nature and origin of these effects. Study of the changes in the kinetics and morphology of the ß - a, reaction produced by varialtions in thermal history was the primary means employed for this purpose. EXPERIMENTAL PROCEDURE The compositions of the alloys used in this in~esti~ation are given in Table I. These alloys were homogenized for 5 days at 1050° C in evacuated (2 x 10 -5 mm of Hg), zirconium-gettered fused quartz capsules. The capsules themselves were enclosed in a porcelain chamber evacuated with a mechanical pump during the homogenization anneals. Upon completion of homogenization, the alloys were cooled to room temperature and then reheated to 550°C for 3 1/2 days in order to transform the alloys to a finely divided mixture of a and TiCr2, and thus provide an approximately constant initial mi-crostructure. Individual specimens were sealed in evacuated and internally gettered Vycor capsules and heat treated as previously described.8,9 EXPERIMENTAL RESULTS Ti-10.64 Pet Cr. This investigation was largely performed on the 0.64 pet Cr alloy. The "base"

Jan 1, 1962

By E. P. Abrahamson

The effect of transition element binary solid solution additions upon the recrystallization temperature of titanium has been investigated. All additions, except columbium and tungsten, raised the recrystallization temperature. A correlation is obtained between the logarithm of the absolute rate of change of recrystallization temperature with atomic percent solute and the number of uuter d shell electrons attributed to the free atom of the solute element in its ground state. The work of Abrahamson, et aL.1-6 on dilute binary solid solution alloys indicated a correlation between the free atom ground state electron configuration of the solute and both the brittle-ductile transition and recrystallization temperature. It is shown in these studies that the number of outer s and d electrons in the solute are of prime importance in determining the absolute rate of change of recrystallization or transition temperature with composition. Furthermore, the limit of initial linearity (in the curve of recrystallization temperature vs at. pct solute) has been shown to be a function of the number of d shell electrons in the solute for dilute iron- and vanadium-base alloys. To date no complete systematic recrystallization study of dilute binary titanium base alloys has been made. This study together with that of zirconium base alloys 6 will provide the data for the comparison of the effect of the same solutes upon two solvents with the same number of outer d shell electrons.

Jan 1, 1962

By W. C. Smith, P. J. Hickey

After a short historical background of the process evolution, this article descvibes present-day plant facilities and operating techniques utilized for high-purity bismuth production. The plant is one of the world&apos;s largest, with an annual output of some one million pounds of refined bismutlz. PREVIOUS papers1 written by staff members of Cerro de Pasco Corp. have referred briefly to the production of refined bismuth. Since the Corporation is one of the world&apos;s foremost producers of high-purity bismuth, a detailed description of the process for extracting the metal may be of general interest. Following a short historical background of the development of the actual process, this presentation will trace the progress of bismuth from its entry into the primary smelting circuits to its concentration in electrolytic lead cell slimes. Our facilities for the treatment of anode muds will be described and the extractive methods given in some detail, with particular emphasis on the techniques which result in the production of refined metal. HISTORICAL BACKGROUND Shortly after Cerro de Pasco began smelting operations at Oroya, Peru in 1922, it became apparent that the dust carried by copper converter gas contained appreciable amounts of bismuth. Although dust collection efficiency was poor prior to building of the 550-ft stack and installation of the central cottrells in 1938, a large stock of dust was accumulated during the intervening years, having the following approximate composition: Oz. per ton Ag - 11.0 Pct Sn — 0.5 Pct Pb - 49.0 Pct Zn - 6.5 Pct Bi - 2.0 Pct Insol. - 1.5 Pct Cu - 0.7 Pct Fe - 2.3 Pct Sb - 3.0 Pct S - 10.0 Pct As - 7.5 In the mid-1920&apos;s, experimental crucible melts of this dust with carbon indicated that most of the bismuth and silver, and some of the lead, could be reduced to a fairly clean bullion. Other products were a small amount of leady copper matte and a slag high in zinc, arsenic, antimony, and lead; this slag contained some tin but only small quantities of silver, bismuth, and copper. After the laboratory results had been confirmed by operation of a small reverberatory, a dust reduction furnace was constructed. The ±10 pct Bi-Pb bullion produced from this operation was stocked until 1930, when an Oroya-designed converter type furnace3 was installed for the elimination of arsenic, antimony, and some lead from the bullion. This process concentrated the bismuth from 10 to about 60 pct. By means of the bismuth process developed4 by W. C. Smith at East Chicago (1909-1914) and the discovery of a method5 for separation of lead from bismuth with chlorine gas in 1929, it became possible to begin production of refined bismuth. Unfortunately, bismuth deleaded with chlorine always contained residual chlorides, and the removal of the chlorides by caustic soda left a lead content of 0.02 to 0.04 pct. This final problem was solved6 by substitution of air-blowing for the caustic treatment, which effectively removed all excess chlorine and gave bismuth which was practically lead-free. In 1934, a pilot electrolytic lead refinery began operations at Oroya. Lead smelting was resumed in 1935 and two years later a 100-ton-per-day lead refinery was put into service. In conjunction with the latter, the present-day Anode Residue Plant was constructed. Until 1940, the plant treated both lead anode slimes and dust reduction bullion. The dust reduction furnace was shut down in that year, and all cottrell dusts (with the exception of the product from the arsenic cottrell) were mixed with pyrite and treated in a Wedge roaster to eliminate all possible arsenic. Calcine from this operation joined the sinter plant feed; hence the bismuth from the copper and lead circuits was collected in the lead bullion and subsequently in lead anode slimes from the electrolytic lead refinery. The latter source has been the only bismuth-bearing material of any consequence entering the Anode Residue Plant from late 1940 to the present. A copper refinery began operating in 1948, and the cell mud from this plant is mixed with lead slimes and processed through the same circuit, though only a small quantity of bismuth is present in electrolytic copper cell residues. BISMUTH INTAKE Present-day routes which are followed by the new bismuth feed from its entry into the primary smelting circuits to its arrival at the Anode Residue Plant are traced schematically in Fig. 1. As illus-

Jan 1, 1962

By G. A. Mancini, V. Bharucha, J. W. Spretnak, G. W. Powell

The characteristics of the motion of the a interface during the "down" transformation was studied in zone-refined iron and dilute binary alloys containing nickel and molybdenum by means of the thermionic emission microscope and high speed photography. The frontal movements were found in all cases to be definitely discontinuous with time and an appreciable number of incremental jumps were found to proceed in the reverse direction (a to b). Molybdenum was found to be particularly effective in increasing the frequency of the increments of transformation from the stable to the metastable phase. A knowledge of the mechanism by which alloying elements affect the hardenability of a steel is desirable from both the practical and scientific viewpoints. It is well established that microstructures consisting of tempered martensite and lower bainite exhibit the best performance in terms of toughness and resistance to crack propagation. The presence of some upper transformation products, namely ferrite and pearlite, is in general undesirable. Various researches have indicated that the ferrite matrix grain structure is a very important difference between the upper and lower transformation products, namely equi-axed vs acicular. Any comprehensive theory of the decomposition of austenite should explain the dependency of the morphology of the matrix on undercooling. The contribution of various alloying elements to hardenability has been determined experimentally and catalogued in considerable detail. A rationalization of the basic mechanism or mechanisms by which individual elements affect the kinetics of the decomposition of austenite to products other than the phase "martensite" has not been evolved as yet. Interest in this problem was stimulated by the effects of minute quantities of boron in hardenable steels. This paper deals with one aspect of this problem, namely the characteristics of the ?-a transformation in high-purity iron and in two carbon-free iron binary alloys. A detailed historical account of the scientific developments in the study of the decomposition of austenite would be a prodigious undertaking and will not be attempted here. There are several excellent reviews in the literature on the formation of pearlite, martensitic reactions, and kinetics of solid-state reactions. The thinking on reaction mechanisms has been influenced to a large degree by the "classical" Tammann nucleation and growth model, in which an embryo springs into being by a fluctuation, and grows to a critical size through atom by atom deposition. Such a process is expected, accordingly, to be diffusion controlled. Considerable research attempting to relate the contribution of alloying elements to hardenability on the basis of their effect on the diffusivity of carbon in iron has not been productive from a mechanistic viewpoint. The formation of pearlite and ferrite has been treated in terms of nucleation and growth processes in which presumably the lattice transformation also occurs by a diffusion process. The other prominently considered mechanism is the "martensitic" or cooperative shearing mechanism. It seems generally, but not entirely, agreed that the phase "martensite" forms by this mechanism, and that it is involved to some extent in

Jan 1, 1962

By C. M. Wayman, J. F. Breedis

The crystallography of the martensitic transformation in the Fe-30 Ni alloy was reinvestigated. The scatter in the habit Plane as determined from measurements on the mid-rib plane was smaller than reported previously, and the orientation relationship was determined from a martensite plate having known direction cosines. From agreement with crystallographic theory and from observations of the morphnlogy of the martensite plates, it is suggested that the mid-rib plane represents the starting region of the transformation. THE crystallography of the martensitic transformation in the iron-nickel system has been the subject of many investigations.&apos;-7 However, for iron alloys containing approximately 30 wt pct Ni, a wide scatter in the reported habit planes exists. In only one instance has a Laue determination of the orientation relationship been made, but the habit plane of the martensite plate studied was not determined experimentally. Because the most successful thermodynamic and kinetic analyses8 of the martensite transformation have been based on Fe-30 Ni alloys, it was considered desirable to reinvestigate the crystallographic features of the transformation in this alloy. Lieberman9 suggested that the most significant information for use in a theoretical treatment involves the determination of all the crystallographic observables from a single plate of the product phase. This was first done in essence by Greninger and Troiano10 for Fe-22 wt pct Ni-0.8 wt pct C, and is the method followed in this investigation. Some theoretical approaches11-13 in describing the martensitic transformation consider the overall transformation distortion to be comprised of a Bain distortion, or lattice deformation (PI, which produces the structure change, and a lattice invariant deformation (G), such as twinning, which together leave the interface or habit plane un-distorted. The incorporation of a rigid body rotation (R) results in a transformation distortion (E) such that the interface plane is left both undistorted and unrotated. In matrix notation, E = RPG where the lattice invariant deformation has "taken place" in the austenite. Bowles and Mackenzie14-16 in formulating a theoretical approach proposed an adjustable scaler quantity, denoted as 6, which represents a uniform dilation in the interface plane. This dilation acts to adjust the lattice spacings of the parent and product structures at the plane of contact. Using the dilation parameter as a variable, these authors were able to account for a continuous variation of habit planes in steels along a curve in the stereogram between {225}A and {259}A. she invariant line strain14 of the transformation is 6 RP, and the corresponding transformation distortion is E/6.) With the dilation parameter known, the invariant line is computed as the triple coincidence of the habit plane, the shear plane of the lattice invariant deformation, and the initial Bain cone.14 The contraction axis for the Bain distortion can be taken9&apos;17 as [010]A, and the correct permutation of the habit plane indices used. Kelly and Nutting 18 have established the shear plane (of twinning) in the tetragonal martensite of Fe-22 Ni-0.8C to be {112)M by means of transmission electron microscopy. The reasonable shear system is then {112}M which is equivalent to {011}A <01l>A. The as-

Jan 1, 1962

By John R. Gould

A mathematical treatment of multiple-pass floating-zone refining of semiconductors, including the evaporation of solutes from the melt at reduced pressure, is presented. Vapor pressures and evaporation rate constants for phosphorus, arsenic, and antimony in germanium have been determined from floating-zone experiments conducted at 10 mm Hg. Rate sensi-tivity of arsenic in germanium has been examined over the range of 1 to 10 in. per hr growth rate. The equilibrium value of the segregation coefficient of arsenic in germanium, as determined by an extrapolation of these data, was found to be 0.09. PFANN has treated the segregation of nonvolatile solutes in the zone-melting process, Bradshaw and Mlavsky2 considered the evaporation of solutes in a vacuum during the growth of crystals by pulling from the melt, and van den Boomgaard3 has shown that it is possible to bring a volatile impurity element homogeneously into an ingot by means of zone-melting under a constant pressure of that element. This paper is concerned with the volatilization of solutes during zone - melting in a vacuum. The mathematical analysis by Lord4 of multiple-pass zone melting is extended to include evaporation of solutes. A method is presented in which evaluations of vapor pressures, evaporation rate constants, and distribution coefficients may be derived from the variation of solute concentration in the floating-zone refining of germanium at 105 mm Hg. EXPERIMENTAL Ingots of zone refined germanium, approximately 1/4 in. in diam and 10 to 12 in. in length, were subjected to several floating-zone passes at 105 mm Hg in order to provide intrinsic material for these studies. These ingots were then seeded in a [Ill] direction and solid-doped to a constant impurity concentration of approximately 1015 atoms per cmS in a forming gas ambient (10 pct H - 90 pct A) at 1/2 atm gage. The resulting crystals were subjected to repeated floating-zone passes at 105 mm Hg and a concentration profile along the length made after termination of each pass. Concentrations were determined from four-point probe resistivity measurements, and proper precautions were taken to prevent contamination during handling. A constant zone length, crystal cross section, and growth rate were maintained during zoning. A stationary coil and moving crystal system were employed for floating-zone growth with neither the section of crystal above nor below the melt rotated.

Jan 1, 1962

By J. W. Spretnak, G. W. Cunningham

Grain growth across the bond region in Pressure bonded copper was found to be mainly dependent upon the presence or absence of microvoids, but it was also found that prior history, bonding pressure, bonding time, and bonding temperature are important variables. An increase in pressure, time, or temperature tends to promote grain growth in the interfacial region. Polygonization is observed after pressure bonding except for specimens previously annealed at temperatures on the order of 1800°F or higher. The dislocation density in bonded specimens was found to be greater in the bond region. THE bonding of metals by the application of gas pressure at elevated temperatures is a relatively new process, having been developed over the past 10 years. The technique, as described by Paprocki, Hodge, and Boyer,l is unique in that assemblies of many parts and complex shapes can be bonded with a negligible amount of deformation. The process thus differs metallurgically from pressure welding, cold welding, and recrystallization welding in that deformation occurs only in a microscopic region whereas, in general, the welding requires severe deformation and may extend the contact surface by a factor of 3 to 10 during the welding. From a practical standpoint, pressure welding is not amenable for bonding large surfaces. During the time in which Paprocki and coworkers were deve1oping the process, West2 established aproc-ess,for bonding aluminum to uranium, and Barnes and Maze? developed a gas-pressure-bonding technique for nickel and copper. Recently, Fugardi and Zambro4 have used equipment similar to that developed by Paprocki and coworkers to establish parameters for bonding stainless steel, aluminum, and zirconium. Most of the investigations on pressure bonding have been empirical in nature and, although methods have been developed for bonding such metals as molybdenum, columbium, titanium, zirconium, and stainless steel, the information concerning the mechanism of bonding is limited. Several workers5"7 have studied the pressure bonding of dissimilar metals in order to gain information on diffusion and formation of inter-metallic phases under application of pressure. Clapson and Robbins8 have shown by a series of annealing studies that voids in the interfacial boundary of roll-bonded copper can prevent movement of the boundary until the voids are spaced far enough apart to prevent pinning. They also indicated that recrystallization and grain growth can eliminate the voids. In this paper it is shown that voids are the major detriment to grain growth across pressure-bonded interfaces, but it is also shown that prior history, bonding pressure, bonding time, and bonding temperature are

Jan 1, 1962

By Nicholas J. Grant, Rolf Nordheim, Bill C. Gissen

The system Cb-Re was examined in detail utilizing pure metals, careful melting techniques, and heat treatments. Metallographic and X-my methods were utilized for phase identification. In addition to soli-dus determinations, the composition limits and mode of formation of the intermetallic compounds 0 and X were determined. The binary constitution diagram Cb-Re has been the subject of a number of investigations.&apos;-7 Two intermetallic phases have been described and tentative diagrams have been proposed. It was the aim of this investigation to obtain a complete and more accurate diagram through the use of purer alloys and improved techniques. The diagram worked out by Knapton7 was published after our experiments were concluded. EXPERIMENTAL METHODS The starting materials were Re powder of 99.95 pct purity, supplied by the Chase Brass and Copper Co., and Cb rondelles of 99.6 pct purity, supplied by the Electro Metallurgical Co. Typical analyses are given in Table I. The alloys were prepared from compacted Re powder and Cb rondelles; for critical compositions master alloys were used. The melts varied from 5 to 50 g and were melted nonconsumably in an Heraeus arc furnace, under ti-tanium-gettered laboratory grade argon. It was necessary to invert the buttons and remelt, followed by crushing and further remeltings, the number of which depended on the nature of the fracture of the alloy. The weight of each alloy was carefully checked after each melting operation. It was found that significant weight losses occurred only when loose Re powder was used. These losses amounted to a maximum of 3 wt pct in such instances, but did not occur after the charge was once molten, regardless of the composition. Typical loss of weight after 4 remelts, including crushing, amounted to 0.2 wt pct. Oxygen pickup during successive melting cycles did not appear to be significant, since the weight gain values never exceeded 0.01 wt pct. Control of the composition of the alloys was not too difficult; however, the problem of homogenization was a far greater one. Optimum alloying conditions were finally achieved by a combination of master alloy production and repeated crushing and remelting cycles. The compositions of the alloys utilized to determine the constitution diagram are listed in Table 11. The weight balance method was used ultimately as the sole analytical method, since repeated checks indicated that it was accurate to 0.2 pct, if the weight losses were small. The results were double-checked by a metallographic study of the homogeneity of the samples, since this was presumed to be the more serious factor. Heat treatments at 1200°C or lower were accomplished by sealing the specimens in Vycor tubes, heating in a Globar furnace, followed by air cooling. This was considered to be an adequate quench because of the very low temperatures involved. For temperatures of 1200" to 1900°, alloys were homogenized and heat treated in a tungsten-filament resistance vacuum furnace. From 1900" to 2750" a tantalum-tube resistance furnace was utilized, operating under a vacuum of 105 mm Hg. The temperature measurements up to 1200" were made by means of platinum-platinum 10 pct Rh thermocouples, with an accuracy of 5°C. For temperature measurements greater than 1200°C, optical pyrometers were used. They were calibrated against a standardized instru-

Jan 1, 1962

By K. J. Gill, P. Chiotti

Thermal, metallographic, and vapor pressure data were obtained to establish the phase diagram for the thorium-zinc system. Four compounds corresponding to the stoichiometric formulas Th2Zn, ThZn2, ThZn4, and Th2Zn17 were observed. The melting points of these compounds under constrained vapor conditions were found to be 1055°, 1105°, 1095°, and 1015°C respectively. Four eutectics exist in this system with the following eutectic temperatures and thorium contents in wt pct: 1040°C, 89 Th; 945°C, 79 Th; 1045°C, 55 Th; and 995°C, 35 Th. The standard free energy, enthalpy, and entropy of formation for the compounds were determined from zinc vapor pressure data. ALTHOUGH the thorium-zinc system has been of technical importance in the commercial production of thorium and more recently of interest to some proposed pyrometallurgical separations processes for reactor fuels or blanket materials no detailed investigation of this system has been made in the past. Some previous work has been reviewed by Hanssen.1 The existence of four compounds, Th2Zn17, ThZn4, ThZn2, and Th2Zn has been established and their crystal structures have been studied by X-ray diffraction techniques.2-4 Smirnov et al.,5 determined the solubility of thorium in zinc and investigated the two-phase region between Th2Zn17 and zinc. They calculated some of the thermodynamic properties for these alloys from emf measurements on the cells Th/ThCl4(fused)/Cl2, C and Th2Zn17(s)+ Zn (l)/ThCl4(fused)/Cl2, C. The possibility of reaction between the anode materials and fused thorium tetrachloride to produce a lower valent thorium salt would have to be resolved in order to evaluate the results obtained. The purpose of the present investigation is to establish the phase diagram for the thorium-zinc system and to determine the standard free energy, enthalpy, and entropy of formation for the compounds formed. MATERIALS AND EXPERIMENTAL PROCEDURES The metals employed in the preparation of alloys were Bunker Hill slab zinc, 99.99 pct pure and Ames Lalboratory thorium. The major impurities in the thorium in parts per million were oxygen—1250, carbon—350, iron—100, nitrogen-75, and silicon—70. The metals in the form of several small massive pieces, total weight about 30 g, were cleaned with acid, washed with water and acetone, and dried just prior to their use for alloy preparation. Tantalum containers were found to be suitable for all the alloys studied and were used throughout this investigation. The metals were sealed inside of small 1-in.-diam tantalum crucibles by welding on preformed tantalum covers. A small thermocouple well made from 1/8-in.-diam tantalum tubing was welded in the bottom of each crucible. These crucibles were enclosed in

Jan 1, 1962

By D. N. Williams

THE present study was undertaken with two specific objectives: measurement of the thermal-expansion coefficient of ß titanium and examination of the effect of solid-solution alloying on the thermal expansion coefficient. Four titanium alloy niaterials were available in the form of annealed 5/8-in. diam rod. Three of these, Ti-8V, Ti-20V, and Ti-6A1-4V, were prepared in the laboratory from 140 Bhn sponge. The

Jan 1, 1962

By R. Steinitz, J. L. Orehotsky

An analysis was made of the influence of floating molten zone traversal on the purification of tungsten rods and the effect of this purification on the brittle -to-ductile transition temperature. The major impurities detectable in the original rods, i.e., molybdenum and oxygen, were reduced by zone refining from 30 to 3 Ppm. Changes in the trace amounts of other impurities could not be quantitatively determined since they were below the limit of detection. Tensile tests on 3-mil wires, drawn from these rods and recrystallized to 17,000 grains per sq mm, showed a transition temperature of 60°C for the zone Purified and 175°C for the original material. 1 HE brittle-to-ductile transition temperature is manifest mainly in the bee metals, iron,&apos; molybdenum, chromium,3 tungsten,4 and niobium. Since many of these metals cannot be fabricated at room temperature in a commercially pure annealed poly-crystalline state, a considerable amount of work has been done on evaluating the influence of purification on the transition temperature in order to determine indirectly whether the fabricability of these metals can be improved by removing impurities. Smith and Rutherford8 showed that the transition temperature of iron is lowered significantly by zone purification. Working with chromium, Edwards, Nish, and wain7 found also that purification appreciably lowered the transition temperature. A similar evaluation has so far not been reported for tungsten, probably because of the difficulties in obtaining tungsten in a purified polycrystalline state. carlson8 and, more recently, schadler9 have purified tungsten rods by floating zone traversal, but after zone traversal, their rods were single crystals. To obtain high-purity polycrystalline tungsten, a technique has to be round for transforming the zone-purified single crystal material into a suitable polycrystalline structure. The purpose of this investigation was to obtain zone-purified tungsten in a suitable polycrystalline state and then to evaluate the effect of zone purification on the transition temperature.

Jan 1, 1962

By G. S. Upadhyaya, A. D. McQuillan

HERE would appear to be a simple relationship between the group number in the periodic table of the early transition metals and the maximum amount of hydrogen which they can absorb.&apos; Thus group IIIA metals (Sc, Y, and La) yield a trihydride in which the metal atoms are on a fcc lattice and the hydrogen atoms occupy both tetrahedral and octahedral interstices. Group IVA metals (Ti, Zr, Hf) form dihy-drides in which the metal atoms are on either a fct or cubic lattice, but in which only the tetrahedral interstices are occupied by hydrogen atoms. In group VA (V, Nb, Ta) the hydrogen-saturated metal attains a composition slightly below that of a monohydride under normal conditions. Finally the metals of group VIA (Cr, Mo, W) do not dissolve appreciable quantities of hydrogen. The manner in which hydrogen solubility disappears on alloying a group VA metal with one from group VIA has previously been investigated.2 It is necessary, in order to obtain a general picture of the reactions of alloys of the early transition metals with hydrogen, to examine a system containing metals from groups IVA and VA in which there must be a change from a fcc to a bee hydride phase. The system chosen for investigation was the pseudobinary system between titanium hydride and niobium hydride. Metallic alloys were prepared by melting iodide-prepared titanium with zone-refined niobium in an argon-atmosphere are-furnace. To ensure homogeneity each alloy was cold-swaged and then heated at 1250°C in a high-vacuum furnace until metallo-graphic examination confirmed its complete homogeneity. Small weighed specimens of the alloys were charged with hydrogen using gaseous hydrogen generated by heating titanium hydride. The apparatus has been described elsewhere.3 Throughout the charging process the hydrogen pressure was kept at about 1 atm while the specimen, initially at 800 °C, was slowly cooled to 150°C over a period of days. The total amount of hydrogen absorbed by each specimen and the room-temperature crystal structure of the hydride powders were determined. The X-ray investigation indicates that the fee hydride phase arises from alloys extending in composition from titanium to 67 at. pct Nb. After a two-phase field lying between 67 and 74 at. pct Nb in which the fee and bee hydrides coexist, all alloys richer in niobium yield a distorted bee hydride. Data derived from parameter measurements are presented in Fig. 1. The atomic volume per metal atom has been plotted against the composition of the initial metallic alloy in order to facilitate comparison of the effects of hydrogen addition in the two phases of different crystal structure. The amount of hydrogen absorbed by each alloy at saturation in terms of the hydrogen to metal ratio and alloy composition is given in Fig. 2. Over the whole range of the fee hydride phase the hydrogen content remains constant, while in the distorted body-centred hydride phase, the hydrogen content increases with increasing titanium content reaching a hydrogen/metal ratio of 1.4 at the boundary of the two-phase region. It seems likely, therefore, that the maximum hydrogen content of the fee hydrides is limited to a hydrogen/metal ratio of 2 because hydrogen atoms

Jan 1, 1962