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By R. M. Rose, D. P. Ferriss, J. Wulff

Single crystals of tantalum, tungsten, and the binary alloys thereof were grown by electron-beam zone melting and tested in tension between 77° and 373°K. The ductile-to-brittle transition temperature increased sharply with solute concentration, for both tungsten-rich and tantalum-rich alloys; apparently, the maximum transition temperature exists near the 50 pet concentration. Twinning was observed to be a consequence of cleavage-crack propagation. Cleavage occurred on(100)planes, and extensive tearing and "river markings" were present. The onset of brittleness could not be associated with any change in deformation mode, the yield point phenomenon, or the large rise in yield stress with decreasing temperature. Cleavage was observed to initiate at either the specimen surface, or subgrain boundaries. The observation was made that the grain boundaries of Polycrystalline materials are probably even better as nucleation sites for fracture, and are responsible for brittleness at high temperatures and lower solute concentrations than those of the corresponding single crystals. TUNGSTEN and tantalum, the two high-melting neighbors in the third transition period of the periodic table, present striking contrasts. Although both are bee, tungsten has far higher elastic moduli, and the highest ductile-to-brittle transition (DBT) of all the pure metals.' Tantalum, however, is ductile at liquid helium temperatures. Large strain aging and yield point phenomena are observed in tantalum,2,3 but only to a lesser extent in tungsten.4 Tungsten work-hardens at a high rate,5 whereas this effect is negligible in tantalum.' Since the mutual solid solubility of these two metals is complete,7 and no ordering has yet been reported in the binary system, the possibility of depressing tungsten's DBT by tantalum additions was considered. Also, tungsten additions to tantalum could produce hard, high-melting alloys which might be ductile at room temperature. Such alloys offered excellent bases for complex alloy development, particularly with regard to the effect of rhenium on Group VI metals.8"10 In addition, there was the opportunity to examine flow and fracture modes in the vicinity of the DBT, with particular emphasis on the correlation between brittleness and fundamental deformation mechanisms. Myers11 has reported that recrystallized alloys with up to 10 pet W in tantalum are ductile at room temperature, but alloys with 20 pct W could not be swaged at temperatures as high as 500°C. The whole spectrum of Ta-W alloys has been surveyed by Braun, Sedlatschek, and Kiefferl2 using sintered powder compacts. In addition to some physical properties they reported a maximum hardness at about 50 at. pet W, dropping to much lower hardness levels for the pure components. They were able to cold work tantalum-base alloys with as much as 30 pet W and to warm work tungsten-base alloys with up to 20 pet Ta by procedures similar to those used for pure tungsten. EXPERIMENTAL In order to study deformation modes and to keep the impurity concentrations at a minimum, electron-beam zone melting was used to prepare single crystals of high purity. The electron-beam zone melting apparatus is similar to that described by Calverley, Davis, and ever" and incorporates a grid control rectifier to maintain control of emission current. Pure metals were refined by making three zone passes at 4 mm per min up the rod. Alloys were prepared by melting together wire of one constituent on a previously melted rod of the major constituent. Subsequently, two zone passes were made in opposite directions to level the composition after the manner suggested by pfann.14 Purification of the starting materials was accomplished by evaporation of the several impurities, and the degree to which this was accomplished is indicated in the chemical analyses of Table I. The uniformity of composition along a zone levelled rod was within the i 1 pet accuracy of the fluorescent X-ray technique used to determine composition. Crystallographic orientation of the

Jan 1, 1962

By L. S. Darken, H. A. Wriedt

An investigation has been made of nitrogen absorption by the lattice defects in a low-carbon steel afte~ Plastic deformation. Specimens in which defects were distributed by various combinations of cold rolling and vacuum heat treatment were equilibrated with controlled ammonia + hydrogen mixtures at 300° to 450°C to study the relation between the solubility and the thermodynamic activity of nitrogen. The results are interpreted in terms of nitrogen being absorbed upon two different types of defect sites, called A sites and B sites. The concentrations of these sites are calculated for specimens with various histories of straining and annealing; and the thermodynamic relations descrihing the equilibrium distribution of nitrogen among the A, B, and ordinary interstitial sites in ferrite are evaluated as follows: THE generalization that the solute atoms in a solid solution interact with imperfections in the solvent lattice is now universally recognized and the subject of an extensive literature. All types of imperfections—point, line, or surface—exhibit these interactions, but the relative importance of each type depends upon its concentration, the strength of its interaction with the particular solute atom, and whether the interaction is attractive or repulsive. The strength and sign of the interaction vary with the vectorial displacement of the solute atom from the imperfection in the crystal. The concentration of lattice defects increases during plastic deformation and the effect of the imperfections upon the solute atoms is usually perceived only after cold work or irradiation. Two experimental methods have previously been used to observe the effects of interaction between nitrogen atoms and lattice imperfections in a iron. Internal friction, which was first used for this purpose by Dijkstra,1 has been applied more often than the electrical-resistivity method of Cottrell and Churchman.2 The method of the present investigation has not been used before.* Uniform specimens of steel with a metastable defect structure are produced by cold rolling and subsequent heat treatment below the recrystallization temperature. Variations in the defect structure are obtained by varying the amount of strain and the heat-treatment conditions. The specimens are then saturated with nitrogen at moderately elevated temperatures in ammonia + hydrogen mixtures having various thermodynamic activities of nitrogen below saturation with Fe4N. From the nitrogen contents of analyzed samples, the metastable equilibria of interactions between the defects and nitrogen can be established and the concentration of sites for nitrogen atoms in the lattice defects calculated. A steel was used in the present experiments instead of purified iron or iron alloys because the amount of nitrogen absorbed at defects is larger in the steel over a much wider range of experimental conditions and could therefore be measured more accurately. The effect of alloy composition is discussed in Part II of this paper; it is sufficient to say here that impurities and phase heterogeneity in ferritic alloys favor the generation and/or retention of larger defect concentrations during plastic deformation and annealing at 300° to 500°C. MATERIALS AND EXPERIMENTAL PROCEDURE The experimental specimens were prepared from stock of a low-carbon steel, which will be called "X steel" here, with the composition: C, 0.12 pct; Mn, 0.43 pct; P, 0.010 pct; S, 0.034 pct; Si, 0.007 pct; As, 0.086 pct; Cu, 0.022 pct; Ni, 0.009 pct; Cr, 0.003 pct. The stock was all from a single ingot made by the basic open-hearth process, which was hot-rolled to strip 0.080 in. thick.. This hot-rolled strip, given the code designation "XH", was the starting material for preparing a series of cold-rolled sheets. The latter are designated "XC27",

Jan 1, 1965

By R. M. Goldhoff, J. W. Spretnak

IN connection with establishing the mechanism by which boron enhances the hardenability of heat treatable steels, this research work has been undertaken. Spretnak and Speiser1,2 indicated the need for studying high temperature effects in boron steels and, chief among these, the possible nonhomogeneous distribution of boron in iron grains. The occurrence of this effect may be of significance in explaining the mechanism of enhancement of hardenability by boron as well as in explaining some of the observed characteristics of boron steel behavior. Primarily, then, this work was undertaken a) to establish whether or not boron is adsorbed in ? solid solutions, b) to determine the nature of any such adsorption effects, i.e., whether it is positive or negative as well as its temperature coefficient, and c) to establish the magnitude of any such effect. While past literature on this specific subject is rather sparse, a number of authors have postulated that the observed temporary loss of hardenability as well as the occurrence of the characteristic boron constituent in these steels is due to the nonuniform distribution of boron in austenite.3-0 Experimental Techniques Attempts to obtain direct evidence of grain boundary effects in boron steels have been unsuccessful, both by using the technique of Chalmers' in which small concentrations of solute made radioactive by irradiation are detected by autoradiographic means, and by means of studying cleavage fractures with the electron microscope.8 The present study attempts the design of experiments to measure the effect of boron on properties which might be subject to variation because of grain boundary effects. A study of the theoretical aspects of grain growth indicates that such studies may be pertinent. Another valid type of experiment involves the measurement in polycrystalline materials of properties whose values depend on the bulk of the grain, being negligibly influenced by grain boundaries. One such property is the lattice parameter measured by X-ray diffraction. The value of the lattice parameter reflects the average conditions which obtain over a relatively large number of atoms in a fixed crystalline lattice, and is therefore mainly dependent on bulk grain material. Measurement of lattice parameter variation over the austenite range of temperature in iron with and without boron should give evidence of concentration variations in the bulk grain material if adsorption effects are significant. Finally, use is made of the Grange and Garvey3 metallographic test for boron in which a characteristic boron constituent can be developed in austenite grain boundaries. The very occurrence of this phenomenon suggests grain boundary enrichment of boron and a study of the occurrence of this constituent and its varation with austenitizing temperature should help to detect grain boundary effects. Materials One lb ingots of pure iron, an Fe-B alloy, an Fe-C alloy, and an Fe-C-B alloy were prepared. The melting technique included an initial melting of electrolytic iron under vacuum followed by remelting under hydrogen and, finally, by melting under argon with the addition of alloying elements. Each ingot was surface machined between meltings. A quantitative spectrographic analysis was obtained on the pure ingot and, in addition, oxygen, nitrogen, and carbon were determined by the vacuum fusion method. The results of these analyses are given in Table I. Semiquantitative spectrographic analyses were performed on the alloy ingots, while quantitative determinations of the alloy additions were obtained. These analyses are shown in Table 11. The cast ingots were subjected to the following sequence of fabrication treatments: forging to 5/8 in. bars, swaging to 0.300 in. rounds, drawing to 0.025 and 0.010 in. wire. Portions of each ingot were retained in the swaged condition for experimental use. For certain portions of the work typical commercial steels were used. These materials were supplied by the Republic Steel Corp., Canton, Ohio, and correspond to AISI 8640 and AISI 86B40 compositions.

Jan 1, 1958

By J. N. Ong, J. P. Ratledge, J. H. Boyce

SINCE German operators opened the Tsumeb mine in the early 1900's, continuous operation has been interrupted only by enforced shutdowns during two world wars and the depression of the 1930's. Original metallurgical practice was blast furnace smelting. This was applicable only to low zinc ore, leaving large tonnages of high zinc ore to be stockpiled on the surface. A gravity concentrator using tables, buddles, and jigs operated for several years, but differential flotation of the ore did not get beyond the experimental stage. When the property was put up for sale by the South African Custodian of Enemy Property there was an estimated 434,000 tons of ore on surface dumps. The dump material, assaying 4.48 pct Cu, 15.8 pct Pb, and 10.9 pct Zn, had become highly oxidized during a stay of many years on the surface. But these dump ores had to be used in evaluating possible metallurgy because the shaft became flooded after the 1940 shutdown and underground ore was unavailable. Many companies examined Tsumeb but quickly lost enthusiasm because of the formidable metallurgical problems presented by the dump ore. However, on the basis of extensive test work, the present company decided that differential flotation would be successful and purchased the property after competitive bidding. Geology and Mineral Association is Complex The Tsumeb mine lies near the northern boundary of South West Africa at an altitude of 4200 ft. The village of Tsumeb is 335 air miles northeast of Wal-vis Bay, territorial port of entry. The orebody is a hydrothermal replacement deposit associated with an irregular intrusion of aplite cutting folded pre-Cambrian dolomite beds. In plan the deposit is a lens of 250x600 ft maximum dimensions. In section the orebody dips 55" south from the surface to 2000 ft, below which there is a reversal in dip to 75" north. Mineralization is localized in the aplite and in the adjoining brecciated dolomite. In the upper levels the ore is largely confined to a single lens, but below the 1890 level massive sulphide ore forms north and south lenses that partially enclose a pipelike body of medium to low grade disseminated ore, part of which is of too poor a grade to mine. Drilling below the 24th, or bottom level, has disclosed that a high percentage of the mineralization from the 3000 to 3300-ft horizons is comprised of copper and lead oxides. The deep oxidation may be local, since it appears due to circulating waters in a major fault cutting the orebody. Tsumeb ranks as one of the highest grade base metal deposits in the world. It is geologically and mineralogically famous for 41 copper, lead, zinc, vanadium, and germanium ore minerals, but its complex mineral assemblage is not attractive to metallurgists. In addition, there is a gradual change in oxidation intensity from the upper levels to the lowest level now operating, which is the 24th. This is well illustrated by the copper minerals. In the upper levels malachite and azurite are predominant, in the intermediate levels chalcocite, and in the lower levels tennantite. Throughout the mine there are sufficient heavy metal soluble salts to activate zinc, and large amounts of depressants are required even for so-called clean sulphide ores. When the same sulphide ore is exposed to prolonged oxidation aboveground, as was the case with the dump ores, reagent requirements become fantastic. Plant Construction First staff members arrived at Tsumeb in March 1947, and by May essential services had been restored and mine unwatering began. In 2 1/2 months company employees built a temporary jig and sorting plant for treating existing dumps to provide a saleable product during high metal prices. Meanwhile, concentrator design and construction was contracted to a South African firm, with subcon-

Jan 1, 1956

By H. F. Webster, C. G. Dunn

Rolling md annealing procedures are described for developing the (110) preferred orientation in tantalum for use as a thermionic-emission materinl where electrodes of a uniform high work function are needed. The development of a (110) [001] annealing texture is also reported. A preferential growth process due to low (110) gas-metal surface energy is considered in explanation of the observed growth of (110) grains. ThE growth of (110)-oriented grains in thin strips of rolled zone-refined tantalum, previously discussed briefly,' is reported together with more recent information on the formation of a (110)[001.] annealing texture, i.e., one where the [001] direction of each grain lies close to the rolling direction. The development of tantalum sheet with a (110) preferred orientation (position of [001 ] directions unspecified) is of importance as a thermionic-emission material in thermionic-energy converters. Since therm ionic-emission properties of cesium-coated crystals vary over a wide range depending on (hkl) a2-7 a single (hkl) preferred orientation is more useful than either several preferred orientations or none. Furthermore, the (110) preferred orientation yields the highest thermionic-emission density for a cesium coverage of less than a monolayer.5-7 A consideration of the stability of the grain structure needed at high operating temperatures suggests that the preferred orientation itself should be produced by annealing processes. Information on annealing textures in tantalum, however, is rather limited. Pugh and Hibbard 8 obtained (111)[112] and (lll)[112] components in a 1400°C recrystallization texture in 95 pct cold-rolled foil; these components were enhanced on annealing at 2500°C. Muller9 rolled 99.97 Ta to 90 pct reduction in thickness in the final stage and noted only a slight sharpening of the rolling texture, with some intensification of the (111)[112] component upon annealing at 1200°C. The experimental procedure followed in the present work stemmed from the idea of using possible differences in (hkl) surface energies to provide a small driving force for growth of grains having the lowest (hkl) surface energy.l0* This would mean using high-purity tantalum processed into thin sheet form and annealed at high temperatures either in a noncontaminating atmosphere or in one producing additional sample purification. EXPERIMENTAL Zone-Refined Tantalum. National Research Corp. tantalum in the form of 1/8-in.-diam rod and of 99.98 purity (53 ppm 0, 15 ppm N, and 8 ppm C) was zone-melted four times. The traversing speed was 4 mm per min. Such treatment increased the resistance ratio, R293k/R20K , where R293K is the resistance of the specimen at 20°C and R20K the re-resistance at liquid-hydrogen temperature, from a value of 25 for the initial rod to 175 for the zone-refined rod (the increase in the resistance ratio provides a measure of purification11,12). Part of a zone-refined rod was rolled unidirec-tionally to a strip 0.003 in. thick and 0.28 in. wide. Samples were given anneals in the range 1300" to 2100°C using ac conduction heating in an oil-free vacuum system. Recrystallization to small grains appeared to be complete at 1300°C. Large grains were formed at higher temperatures, but these were not entirely strain-free, some grains showing asterism in Laue X-ray patterns and some displaying a range in orientation. Part of the difficulty was caused by thermal expansion of the tantalum strip as it was held between fixed supports. However, in a different arrangement with the tantalum freely suspended in a tantalum can, high-frequency induction heating in vacuo at about l0-6 Torr produced

Jan 1, 1964

By G. K. Manning, W. E. Few

T has been known for some time that both'inter-granular carbide and intergranular oxide phases cause brittleness in molybdenum. Parke and Ham' indicated that 0.0025 pct 0 present in molybdenum after solidification from the melt was sufficient to induce intergranular brittleness during forging. However, material containing 0.06 pct C could still be forged. However, adding this amount of carbon to insure deoxidation causes the formation of carbides on freezing. These carbides are precipitated at grain boundaries, and Rengstorff and Fischer' have shown they have an unfavorable effect on the room-temperature ductility of molybdenum. Take? in 1928 proposed that the solubility of carbon was a constant value of 0.30 pct from room temperature up to 1800°C. In 1935, Sykes, Van Horn, and Tucker' obtained X-ray data suggesting that the solid solubility of carbon in molybdenum was between 0.07 and 0.09 pct at temperatures from 1500" to 2100°C. The a-solubility line for carbon was included in the Mo-C diagram given in the Metals Handbook as a tentative line based on the data of Sykes, Van Horn, and Tucker. In order to determine the partial phase diagrams for these systems, it was necessary to construct a high-temperature furnace suitable for heat treating molybdenum at temperatures up to 4000°F. A molybdenum resistance furnace was built for this purpose in which samples could be heat treated in a purified atmosphere and quenched from any desired temperature.' Experimental Work Solubility of Carbon: Arc-cast molybdenum supplied by the Climax Molybdenum Co. and 18-gage molybdenum wire samples produced by powder metallurgy at the Fansteel Metallurgical Co. were used in determining the a-solubility line for the MO-C system. The cast molybdenum contained 0.032 pct C initially. Two lots of 18-gage wire were used, one containing 0.011 pct C and the other 0.005 pct C initially. All material contained a carbide phase as received. Fig. 1 illustrates the carbides found in the untreated material. Heat treatment in a purified hydrogen atmosphere was found to reduce the carbon content in the as-cast molybdenum. Purified argonT also decarburized molybdenum samples at temperatures above 3500°F; however, the carbon content remained constant during heat treatment in purified argon at lower tem- peratures. The argon was purified by passing it over titanium at 750 °C and then through a magnesium perchlorate drying tower. The hydrogen was purified by passing it through a commercial hydrogen deoxidizer, followed by a drying tower. Specimens having different initial carbon contents were heat treated in argon at 3500°F for periods ranging from 5 min to 5 hr and were analyzed for carbon. Samples of the same final carbon content had the same microstructures regardless of time at temperature. Furthermore, a gradient between center and surface in the amount of undissolved carbide particles present was never observed. It was concluded that at these low carbon levels, and at the high temperatures involved, diffusion proceeds so rapidly that the specimen is always substantially homogeneous in carbon content, in spite of the gradual loss in carbon. Based on the above findings, the following procedure was used to determine the carbon-solubility limit at 3000°, 3500°, and 4000°F. At each of these temperatures, a number of samples were heat treated, as shown in Table I, and rapidly cooled to room temperature. Since the samples lost carbon in proportion to the length of time heated, a series of samples were obtained of varying carbon contents. By use of a rapid cooling rate, the phases present at the high temperature were retained at room temperature. All samples were examined microscopically. Those found to contain either no excess carbide phase or only a very small amount were then analyzed for carbon. The samples actually analyzed for carbon

Jan 1, 1953

By F. W. Jessen, James N. Howell

INTRODUCTION The determination of cloud points has to date been limited to rather transparent oils, visual observation of the formation of a solid phase being the criterion for the standard ASTM D 97-47 method. The need for a quiclc and simple method for determining cloud points under dynamic conditions for opaque crude oils became necessary in a study of fundamental aspects of paraffin deposition from crude oils. PREVIOUS WORK The determination of cloud points in opaque oils by viscosity temperature curves is fairly new, Young' described a method employing the capillary tube principle. No information exists relative to the determination of cloud points of crude or refined oils under dynamic conditions. Shock' noticed that deposition of paraffin from crude oils took place at temperatures at or below the temperature at which a sharp inflection point occurred in the viscosity-temperature curve. This observation indicates a possible correlation between this temperature and the cloud point of the crude oil. Reistle and Vietti1 have reported that when crude oils containing small amounts of asphaltic materials were heated to temperatures sufficiently high to solubilize these materials and immediately cooled the pour point of the crude oil was lowered as much as 70°F. Sachanen\ asribes this effect to the action of colloidal asphaltenes in preventing the formation of the crystalline structure necessary to maintain the oil in a rigid state. At high temperatures, asphaltenes are peptized, and the paraffin crystals formed at these temperatures adsorb the colloidal asphaltenes on their surface thereby hindering further growth of the crystals. Reistle" found, however, that such heating and cooling of crude oils had no effect upon the cloud points. This latter work dealt with a crude oil of fixed composition, and the question immediately arises as to the effect of varying the concentration of asphaltic materials on the cloud point. APPARATUS AND PROCEDURE All viscosity measurements were made with a Bendix Ultra-Viscoson. The Bendix Ultra-Viscoson, which consists of a vibrating probe and an electronic computer. measures viscosity by exciting a thin alloy steel blade on the end of a probe by short electrical pulses in damped oscillation at 28 kilocycles. The blade vibrates longitudinally with an amplilude of less than 55 micron or 20 millionths of an inch. Energy to protlucc this excitation is generated in he computer and transferred to the probe through the connecting cable. The oscillating blade is magnetostric-tive, i.e., it is capable of transforming electrical energy to mechanical energy in the ultrasonic range. Ultrasonic waves are produced in the material surrounding the blade by the oscillating motion of the blade causing layers of the material to slip back and forth over one another at a known frequency. The electronic computer calculates the energy required to produce the sliding motion which is in turn proportional to the viscosity of the material. Actual values of viscosity times density (centi-poise X grams/cc) are indicated on the computer and a continuous D-C signal is provided which is fed into a type 153 Electronic Recorder (manufactured by Brown Instruments Div. of Minneapolis-Honeywell Regulator Co.) The liquid sample container was fabricated from a Lucite cylinder and jacketed by a Luicite water bath. Early experiments using glass and steel sample containers were not satisfactory. since the Ultra-Viscoson was apparently affected by the alterzltion of the magnetic fields surrounding the probe by stresses set LIP in the glass and steel as it cooled. The procedure for determining viscosity-temperature curves was relatively simple. The temperature ot the sample was raised sufficiently high to solubilize all paraffin and asphalts present. After heating, the oil sample was immediately transferred

Jan 1, 1957

By P. K. Koh, G. C. Dunn

Si-Fe single crystals in a number of selected orientations were cold rolled 70 pct and analyzed to obtain quantitative (110) pole figures. Stable end orientations were ddetermined, and the effect of orientation on deformation behavior was investigated. WHEN single crystals are cold rolled sufficiently, they rotate into end orientations that are stable or unchanged in position with additional deformation. The end orientations of heavily cold-rolled iron crystals, positioned in holes in copper to limit lateral flow and to simulate polycrystalline conditions during deformation, were determined by Barrett and Levenson.' They found that the sum of the end orientations, a pole figure for all the crystals studied, reproduced the essential features of the cold-rolled texture of polycrystalline iron. In. an investigation of Fe-Si alloys, Barrett, Ansel, and Mehl' observed little effect of silicon content on the textures of heavily cold-rolled samples. Since alloys with less than 4 pct Si are known to have the same slip systems as iron," it seems logical to expect that they would also have the same end orientations as those for iron. Whereas Barrett and Levenson in their study of single crystals were interested in the problem of the origin of the cold-rolled texture of polycrystalline iron, the present authors are more interested in the final cold-rolled textures of single crystals of Si-Fe from the point of view of their relationship to subsequent recrystallization phenomena which will be reported in another paper. Nevertheless, such points as the tendency of an end orientation not to rotate (stability), the tendency of a pole concentration to spread out, and the tendency of the crystal to widen during cold rolling become interesting separately when the initial orientations are selected already in end orientations. Also the initial orientations having a [I101 axis parallel with the transverse direction, which include the two end orientations (111) [Ti21 and (001) [110], comprise a series that needs further clarification regarding the way such crystals rotate during deformation. Finally the present use of quantitative pole figure methods* represents an advance over the X-ray photographic method employed by Barrett and Levenson in their work on end orientations. The present investigation provides information on the cold-rolling behavior of two groups of Si-Fe crystals: 1-—crystals initially oriented in recognized end orientations for iron crystals with a [I101 direction parallel with the rolling direction, and 2— crystals initially oriented with a [I101 direction 90" to the rolling direction and in the rolling plane. For the second group, there is a 90" range between the (001) [110] orientation and the (110) [001] orientation. Since the 35" portion of this range from (110) [OOl] to (111) Di2] was included in a previous investigation," only the remaining 55" portion from (111) fii2] to (001) [I101 needs further consideration. Also, since both (111) [xi21 and (001) [I101 are end orientations for iron crystals,' there might be a critical orientation* or orientation range be- • W. W. Martin and C. G. Dunno noted that (112) [Till was such a critical orientation. tween them such that early in the deformation an orientation within this critical range splits into two orientations. Upon further deformation, these two orientations rotate to produce a final texture consisting of (001) [1101 and (111) [?i2] components. The end orientations obtained are discussed in connection with the work of Barrett and Levenson, while the observed tendency for lateral flow of crystals in these orientations is treated in terms of the theory of Hibbard and Yen.' Lateral flow according to the theory increases with deviation of the plane containing the rolling direction and the slip direction from a position perpendicular to the plane of rolling. Experimental Procedure Single crystals in sheet form with preselected orientations were prepared by methods that have been described elsewhere." Three lots designated A, B,

Jan 1, 1956

By Larry Kaufman

A useful method for estimating the entropy of NaCl type compounds has been developed by combining the Debye theory of specific heat with the Lindemann formula. This method pemnits calculation of the entropy from a knowledge of the atomic weight, atomic volume, and melting point of the compound. Comparison of the calculated and observed entropies of 35 NaCl type compounds over a wide temperature range yields good agreement thus establishing the usefulness of the method. Application of the method to other crystal types is also discussed. KUBASCHEWSKI~ has suggested a useful method of estimating the enthalpy of formation of inter-metallic compounds from a knowledge of the crystal structure, lattice parameter, and heats of sublimation of the component elements. This method is quite valuable in predicting the tendency for compound formation in a given system and is of particular value in considering systems for which no experimental data are available. In order to supplement the enthalpy calculation afforded by Kubschewski's method, it would be of value to be able to estimate the entropy of compounds so that the entropy and free energy of formation could be evaluated. Although a considerable body of such data determined by calorimetric and equilibration techniques exists at present, the difficulty of making such measurements (particularly at high temperatures) and the ever increasing number of new compounds which are of interest make the desirability of such a computational method clear. This paper deals with a method for calculating the entropy of a compound from a knowledge of the atomic weight, atomic volume, and melting point. Since these data are generally easier to determine and therefore more readily available than thermo-dynamic data, they should provide an additional tool in estimating the stability and reactivity of compounds at high temperatures. I) THE ENTROPY OF PURE METALS As a first approximation, the specific heat of a pure metal can be represented by a sum of terms where C,($/tI is the vibrational specific heat calculated on the basis of the Debye theory, lo4 TC, (0/T) is an approximation to the Cp - C, correction. T is the electronic specific heat, and Cp (p) is the magnetic specific heat. Although the Debye theory does not provide a complete description of the vibrational specific heat, i.e., the Debye temperature 0 is not a constant, it does provide a good approximation when used properly. Blackman6'7 has written several reviews on this subject discussing the different values of 0 determined by various methods (specific heat, X-rays, elastic constants, electrical resistivity, and so forth), as well as the observed temperature dependence of 0 with T. In the present case the 0 in Eq. [I] naturally refers to the specific heat 0. The variation of Debye 0 (as determined from specific heat measurements) with temperature is observed to exhibit its most radical behavior at very low temperatures. At higher temperatures the 8 values are observed to become more nearly constant. Blackman6'7 has presented the variation of 0 with temperature for several metals. His tabulation is reproduced in Table I. Reference to Table I shows that above a certain temperature level, 0 remains fairly constant. The value of 0 which is most useful in computing the specific heat, and hence the entropy, is the value of 0 in the range 0/6 « T « 0. In 1910, Lindemann' suggested a relation for estimating Debye 0 values. According to this formula, where V is the atomic volume, T is the melting point in 'K, M is the atomic weight, and CL is a constant. Mott and Jones9 present this formula and state that there is at present no satisfactory theoretical explanation, but that it does have an empirical basis. By using the valuesof 0 in Table I along with known1' values of M, T, and the molar volume VM, where the Lindemann constant can be evaluated. This

Jan 1, 1962

By M. S. Hunter, D. L. Robinson

An extremely fine subgrain structure found in aluminum and aluminum alloys is shown and a method for revealing this structure is described. The appearance and some of the characteristics of this structure are described and the possible significance of subgrain structure in terms of chemical, electrochemical, and metallurgical processes is considered. GRAINS and grain boundaries, which constitute the principal manifestations of the crystalline aggregates known as metals, play such an important part in determining the characteristics and properties of metals and alloys that their nature and behavior have long been of much concern to the met-allographer. Many investigators have speculated on the possible existence of a finer structure within the usual grain structure and, through X-ray diffraction and metallographic techniques, have revealed evidence that such finer structures exist. Among these structures are the mosaic blocks and domains described by Burgers1 and others in their contributions on crystalline structure and the dislocation theory, the small units associated with polygoniza-tion described by Cahn,2 and the intragranular blocks revealed more recently by Lacombe and Beaujard.3 his paper describes some novel methods for clearly revealing a very fine granular substructure within the usual grains of pure aluminum and aluminum alloys. It also compares the characteristics and behavior of this subgrain structure with those of the ordinary grain structure and gives some examples of the manner in which this substructure may influence the characteristics of aluminum alloys. Metallographic investigations of aluminum and its alloys have dealt extensively with the functions and behavior of grains and grain boundaries and have evolved a definite concept of the relation between grain structure, orientation and physical, mechanical, chemical, and electrochemical behavior. During the examination of etched samples, a roughening or mottling of the body of certain grains has occasionally been observed. Such roughening obviously represented differential attack by the etching solution, but its true significance was not at first realized. It is now known that this roughening probably rep- resented a subgrain structure, although the particular etching treatments used were not capable of revealing this subgrain structure clearly. Also, in practically all cases, the subgrains were apparently far too small to be resolved by the light microscope. Recently, a method has been developed for revealing clearly the subgrain structure of most aluminum alloys. This method is somewhat unique in that it eliminates much of the usual tedious mechanical polishing and the attendant danger of a surface layer of flowed metal and at the same time is simple, rapid, and effective. It involves the use of the Alcoa R5 Bright Dip, a patented chemical polishing treatment licensed by Aluminum Co. of America. This treatment produces a bright, highly polished surface at least the equal of any mechanical polish and also etches the subgrain boundaries as well as the ordinary grain boundaries to reveal both the grain and subgrain structure simultaneously. Metallographic specimens to be examined are taken through the customary grinding and polishing operations used for aluminum alloys.' The usual care required in the final polishing operation to prevent a flowed surface layer and to obtain a high polish is not necessary, however, because any flowed layer is eliminated and a high polish is produced by the final immersion in the Alcoa R5 Bright Dip. Depending on alloy type, this dip takes from a few seconds to about 3 min, after which the sample is rinsed well, blown dry, and is ready for examination. The substructure can be revealed by some of the usual metallographic methods such as electropolish-ing or mechanical polishing and etching but no method has been found which is the equal of the new chemical polishing treatment. Mechanical polishing followed by the usual metallographic etching is not entirely satisfactory for revealing this substructure, probably because of the flowed surface layer resulting from the mechanical polish. If the usual etching methods are prolonged sufficiently to remove this layer, the specimen surface becomes quite rough and the substructure is not defined clearly.

Jan 1, 1954

By W. L. Crentz, E. E. Donath, D. Doherty

IN 1948, the United States used nearly six million barrels of petroleum products every day. Although substitution of synthetic fuels for the natural petroleum product is not here yet, large quantities of special-purpose coal will be required in ever-increasing volume as the domestic production of oil from other sources fails to meet demand and the production of synthetic fuels begins. Petroleum economists do not agree as to when the shortages of domestic oil will appear; but the increasing per capita consumption of oil, coupled with a constantly growing population drawing on a potential domestic oil supply estimated to be 85 billion barrels, sooner or later will result in demand exceeding domestic supply. When this situation comes about, the excess demand will be either eliminated by curtailment of consumption or the demand met by increasing importation of foreign oil or by the production of synthetic fuels. The first recourse would definitely retard the heretofore unbroken rise in American living standards, while dependence upon a foreign oil supply during a war or other emergency would be dangerous. On the other hand, the enormous coal reserves in the United States, plus sizable deposits of oil shale, indicate adequate means of augmenting a diminishing domestic oil supply. Some idea of the impact of an expanding synthetic liquid fuels program on the coal-mining industry may be gathered when it is considered that to supply just half of our present-day petroleum needs synthetically from coal would increase the coal output by about 500 million tons annually, using an 11,900 Btu bituminous coal as the plant feed. If either a subbituminous coal or lignite were used, the quantity required would be materially increased. Synthetic Fuel Processes: The principal synthetic fuel processes using coal as a raw material are the Bergius, or coal-hydrogenation process, and the Fischer-Tropsch, or gas-synthesis process. These two processes not only produce different end products, but the preparation of the coal used in each presents its own individual problem to the coal-preparation engineer. The hydrogenation process brings together a mixture of dry, finely powdered coal, catalyst, and heavy oil to form a paste. Addition of hydrogen under rather high pressure and temperature conditions brings about transformation of the coal to a liquid product, from which a high-grade gasoline and other motor fuels may be obtained. The Fischer-Tropsch process requires the production of synthesis gas, a mixture of carbon monoxide and hydrogen. At the Bureau of Mines Louisiana, Mo., demonstration plant, this gas is being made by reacting dried pulverized coal with carefully controlled volumes of oxygen and superheated steam. After purification and in the presence of the proper catalyst and suitable conditions of pressure and temperature, the hydrogen and carbon monoxide components of the synthesis gas react to form motor fuel. The two processes are not competitive but rather com-

Jan 1, 1951

By E. E. Donath, W. L. Crentz, D. Doherty

IN 1948, the United States used nearly six million barrels of petroleum products every day. Although substitution of synthetic fuels for the natural petroleum product is not here yet, large quantities of special-purpose coal will be required in ever-increasing volume as the domestic production of oil from other sources fails to meet demand and the production of synthetic fuels begins. Petroleum economists do not agree as to when the shortages of domestic oil will appear; but the increasing per capita consumption of oil, coupled with a constantly growing population drawing on a potential domestic oil supply estimated to be 85 billion barrels, sooner or later will result in demand exceeding domestic supply. When this situation comes about, the excess demand will be either eliminated by curtailment of consumption or the demand met by increasing importation of foreign oil or by the production of synthetic fuels. The first recourse would definitely retard the heretofore unbroken rise in American living standards, while dependence upon a foreign oil supply during a war or other emergency would be dangerous. On the other hand, the enormous coal reserves in the United States, plus sizable deposits of oil shale, indicate adequate means of augmenting a diminishing domestic oil supply. Some idea of the impact of an expanding synthetic liquid fuels program on the coal-mining industry may be gathered when it is considered that to supply just half of our present-day petroleum needs synthetically from coal would increase the coal output by about 500 million tons annually, using an 11,900 Btu bituminous coal as the plant feed. If either a subbituminous coal or lignite were used, the quantity required would be materially increased. Synthetic Fuel Processes: The principal synthetic fuel processes using coal as a raw material are the Bergius, or coal-hydrogenation process, and the Fischer-Tropsch, or gas-synthesis process. These two processes not only produce different end products, but the preparation of the coal used in each presents its own individual problem to the coal-preparation engineer. The hydrogenation process brings together a mixture of dry, finely powdered coal, catalyst, and heavy oil to form a paste. Addition of hydrogen under rather high pressure and temperature conditions brings about transformation of the coal to a liquid product, from which a high-grade gasoline and other motor fuels may be obtained. The Fischer-Tropsch process requires the production of synthesis gas, a mixture of carbon monoxide and hydrogen. At the Bureau of Mines Louisiana, Mo., demonstration plant, this gas is being made by reacting dried pulverized coal with carefully controlled volumes of oxygen and superheated steam. After purification and in the presence of the proper catalyst and suitable conditions of pressure and temperature, the hydrogen and carbon monoxide components of the synthesis gas react to form motor fuel. The two processes are not competitive but rather com-

Jan 1, 1951

BECAUSE of the impetus given to placer mining since the price of gold was advanced to $35, several types of small dredges have made their appearance, especially in the Lincoln and Oroville areas of California. Some of these are known as "doodle bugs," and have been given considerable publicity, though many believe their performance has been overrated and that complete costs of construction and operation, if known would not put them in so favorable a light. Fig. 1 is a doodle bug owned by E. M. Clark and operated near Lincoln, Calif. It is understood that it was abandoned because of inability to handle deep ground. A similar machine that has been operated-profitably by Comstock Placers is shown in Fig. 2.

Jan 1, 1938

By J. Gross

G. H. Clevenger, Chairman of the Milling Methods Committee of the Institute, made the following introductory remarks: "Several years ago, a number of us felt that the time was ripe for a fundamental investigation of crushing and grinding. At the outset, it appeared that the first thing we needed was a yardstick whereby grinding efficiency could be measured. "The U. S. Bureau of Mines has been most generous in cooperating with the Milling Methods Committee in getting this work well under way. John Gross, who served the committee for a year as secretary, was placed in charge of the investigation and has been ably assisted by S. R. Zimmerley. "Messrs. Gross and Zimmerley will now present the Progress Report covering their work to date." PROGRESS REPORT J. Gross, Salt Lake City, Utah. -This has not been a simple problem, and when I tell you that we can give you a verbal report of what we have done during three years in five or ten minutes you will realize that we have necessarily done a great deal of work that does not appear in the final results. We have been in a virtually new field. Therefore, we have had to feel our way at each step so as to be fairly sure we were correct. The first thing that was realized in this problem was that unless we had some method of measuring what happened when we crushed an ore, we might as well quit and not go further. We realized that if we tried to measure the results of crushing or grinding by the ordinary sizing test we would not get anywhere. We could sieve down to say 200 mesh fairly accurately; we could even go one sieve size further with a little less accuracy, and then we were absolutely lost, unless we went into microscopic measurement. Even this latter method would not have been satisfactory. The question was: what were we going to measure? If we were going to measure size, we might measure one particular dimension of a particle and be off 200 per cent. or more. If we tried to measure surface, we would have something tangible; the surface of a particle, no matter how irregular, is something definite, far more definite than any linear dimension would be. Moreover, if we could measure surface, we would immediately have a method of checking the Rittinger law as to whether it was or was not correct. So the first thing that we sought was a method whereby we could measure surface on crushed particles or, we will say, on particles; it would not make any difference whether crushed or not. It then became a question of what kind of particles we were going to use in obtaining a method for surface measurement. We realized that it would be rather a com-

Jan 1, 1928

R. V. NorHis, Wilkes-Barre, Pa. (communication to the Secretary*) : The electric-haulage plant of the Short Mountain Colliery of the Lykens Valley Coal Co., mentioned by Messrs. Stoek and Harris as the earliest underground electric plant in the United States (and, I believe, the second in the world), was started July 23, 1887. The plant, designed by W. M. Schlessinger, consists of two motor-cars, each weighing about 5 tons and equipped with a 32-h.p. Union Electric Go. motor. The original general construction of the motor-cars is shown by Mr. Stoek; but they were rebuilt, the same year, with some important improvements in design; and, except for strengthening the frames and replacing the original pig-iron weights by a casting, they have not been greatly changed since that time. The generating-plant consists of two Union Electric Co. dynamos of 65-h.p. each, driven by an old 18- by 48-in. plain slide-valve engine; the ordinary voltage is 450 and the amperage varies from 40 to 200; the average indicated h.p. of the engine is about 75, with a steam-consumption of about 75 lb. per i.h.p. per hour; and as the cost of steam at this colliery is 8.11 cents per 1,000 lb.,the steam-cost per day is about $4.56.

Jan 1, 1904

By S. Terry, W. Callender, R. J. Cornelius

When a dry ball-mill grinding circuit was in- stalled at the pellet plant of Hamersley Iron Pty. Ltd., it was something of a pioneering venture, since this was one of the first instances where such a circuit had been applied to iron ore on a major scale. The Hamersley pellet plant is located in Dampier on the coast of Western Australia. The feed for it consists of -8mm fines produced as a screened product at the Mt. Tom Price mine 186 miles inland from Dampier. It was these fines that encouraged the choice of a dry grinding facility for the plant. At the outset, tests had shown that the fines could not be filtered satisfactorily with a wet grinding system. At the pelletizing plant, the fines are stockpiled, reclaimed, dry ground in ball mills, formed into pellets on balling discs, hardened on an indurating line, and stockpiled for shipment overseas. These operations are shown in Fig. 1.

Jan 7, 1969

By TRUMAN S. FULLER

THE GREAT INTEREST in decomposition and trans- formation, so evident in the study of alloys during the last two years, was reflected in the many papers on this subject, presented at the first session of the Institute of Metals, Tuesday morning. Dr. F. A. Thomson, of Montana State School of Mines, presented the first paper by C. Wilson, H. F. Silliman, and E. C. Little, "Rate of Precipitation of Nickel Silicide and Cobalt Silicide in the Hardenable Copper-nickel-silicon and Copper- cobalt-silicon Alloys." Dr. R. F. Mehl, in discussing this paper, stated that the title was somewhat deceptive, as it indicated that the rate of precipitation is determined; the method used is a measurement of electrical conductivity and hardness, neither of which is suitable for a quantitative measurement of rates of reaction or precipitation in the solid state. Hardness is also uncertain because it depends so much upon particle size. Of the various methods proposed for the study of rate of reaction and precipitation the evaluation of volume of reaction produced from the area of photomicrograph is the best.

Jan 1, 1933

By Franklin G. Pardee

IN 1920 the Minnesota Tax Commission estimated a reserve of 1,341,674,538 long tons of iron ore in Minnesota, the Michigan State Tax Commission report showed 199,092,855 long tons in reserve in that state, and the Wisconsin Geological Survey set the Wisconsin reserves at 21,500,000 long tons. The total reserve that year for the Lake Superior District amounted to 1,562,267,393 long tons. Ten years later the reserves of iron ore in these same districts were Minnesota 1,235,227,510, Michigan 168,349,823, and Wisconsin 23,000,000, or a total of 1,426,577,333 long tons. The decrease in ore reserves in this ten-year period was 135,690,060 long tons, but the shipments were 520,746,975 long tons. In other words, the ten-year depletion in reserves was only 8.68 per cent. If similar conditions carry into the future this calculation would indicate a life for the ore reserves of the Lake Superior region of over 100 years.

Jan 1, 1933

By J. F. K. Brown

ANTHRACITE?S satisfactory showing in 1942 was accomplished in the face of adverse conditions, such as the loss of man power to the active services and to other industries, and the difficulty and delay in obtaining the necessary materials and equipment required in mining operations. Although the in- creased output was stimulated by the war, and thus does not impress one as contributing to continuing improvement in the industry, nevertheless the year witnessed several efforts ant1 consideration of others that have the appearance of permanent progress.

Jan 1, 1943

By AIME AIME

As already announced, the XCIIId meeting of the Institute will be held at Toronto, beginning July 23, 1907. Hotel Headquarters will be at the King Edward Hotel, in which also the sessions will be held. The Queens, Rossin, Wallen, Iroquois and Palmer are good hotels not far from the King Edward. Members must secure their hotel-accommodations beforehand, by direct correspondence with the hotel they select. For those who neglect this precaution, the Local Committee will doubtless do what it can, but is unable to promise anything. Correspondence concerning this meeting (including notices of intention to attend it) should be addressed hereafter exclusively to Mr. W. G. Miller, Provincial Geologist, Bureau of Mines, Toronto, who is the representative of the Local Committee. The excursion to Cobalt, Lake Tenagami, Sudbury, etc., arranged by that Committee, involves the use of a special Pullman train for meals and lodging. After waiting a reasonable time to hear from members, the Local Committee has made its contract for Pullman cars. According to its latest report, there was still room for additional excursionists. Under this head, application made immediately to Mr. Miller may not be too late. Sessions for the presentation of papers, etc., will be held at the King Edward Hotel on Tuesday afternoon, July 23, and Wednesday morning and afternoon, July 24. The following papers have been accepted: 1. Sonic Reflections on Secrecy in the Arts, by James Douglas, New York, N. Y. .2. The Wilfley Table, by R. H. Richards, Boston, Mass. 3. The Tar-Sands of the Athabaska District, by' Robert Bell, Ottawa, Can. 4. The Occurrence of Nickel in Virginia, by Thomas L. Watson, Blacksburg, Va. 5. Coal-Briquetting in the United States, by E. W. Parker, Washington, D. C.

Jul 1, 1907