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By J. B. Newkirk, A. H. Geisler

INTRODUCTION CERTAIN of the permanent magnet alloys provide ideal systems for the study of the kinetics of the precipitation reaction and the correlation of structure with properties. One such system, Cu-Ni-Fe, was found by Bradley1,2 to exhibit a coherent transition state in the precipitation process analogous to that reported for Al-Cu alloys somewhat earlier.3 The attractiveness of some permanent magnet alloys for study lies in the fact that vertical sections of the ternary phase diagram in certain regions of composition (Fig I) have as their prototype the binary Ni-Au diagram. Alloys of this type decompose into products that have the same crystal lattice type but only slightly different lattice parameters. The advantages that such alloy systems offer for study over the usual in which an intermetallic compound is formed are many: I. Since the precipitate has the same crystal structure as the matrix, complex atomic movements are not required to form the new lattice. 2. Similarly, complex orientation relationships are not involved for both the matrix and the precipitate would be expected to have the same orientation. 3. Small disregistry of the decomposition products at equilibrium (in contrast with Cu-Ag alloys) is conducive to extensive coherent growth in the transient state and thus the transition lattice can be detected by the usual X ray diffraction methods. 4. Finally, the relative quantities of precipitate and depleted matrix can be varied from o to 100 pct* thus permitting wide freedom for the study of the effect of composition on coherent growth and properties. In the Cu-Ni-Fe alloys of appropriate composition, the face-centered cubic precipitate and also the depleted matrix when first formed are coherent with the parent matrix.1,2 The two have the same [ao] parameter as the original matrix but they are both tetragonal; the precipitate has an axial ratio c/a < I while that of the depleted matrix is c/a > I. When coherency is lost they assume the normal face-centered cubic structure with the depleted matrix having a lattice parameter greater than the original matrix and that of the precipitate less. Such a mechanism would also be expected for Cu-Ni-Co alloys because of the similarity in constitution but this had not been demonstrated. The present investigation was conducted on a Cu-Ni-Co alloy. The constitution diagram and magnetic properties of these alloys have been fairly well established 4,5 however, no previous determinations of mechanism of precipitation and no correlation of structure with properties had been made. Thus, an alloy of this system was chosen for a comprehensive investiga-

Jan 1, 1948

By H. S. Rawdon

One of the most vital problems in the manufacture of steel at present is the occurrence of the defects that have been popularly termed "snow flakes," "flakes," or "scabs." Particularly is this the problem of many manufacturers who, during the past 2 yr., have undertaken large-scale production for the first time. A study of the microstructure of such defective material throws considerable light upon the nature of these defects and is essential before measurcs may be taken for the elimination of the defects. Flakes do not appear to be found in the plain carbon steels; they have been found. however, in abundance in some of the simple alloy steels that are being used in such vast quantities; vie., nickel steel of the approximate composition, 0.40 carbon and 3.5 per cent. nickel, and in the chrome-nickel type. The present article summarizes the characteristic features of defective steel of the flaky type as they have been found by laboratory study of numerous specimens, and it aims to show the conditions within the metal that are favorable to the occurrence of this type of defect without entering into the details of mill practice (size of ingot, design of molds, rate of cooling, distribution of cooling stresses, etc.), all of which conditions appear to play a role in the production of these defects. MacrostrUctURe To one familar with flaky steel, the appearance of "snow-flakes" is unmistakable and is not to be confused with other types of defects. Figs. 1 to 6 show the appearance of fractures of steel showing this type of defect; the white silvery area, which always has the appearance of being of a very coarsely crystalline structure, in the specimen stands out in bold contrast to the darker background and readily justifies the use of the term "snow-flakes." Fig. 1 shows the appearance of the faces of the two halves of a nickel-steel forging that has been split to show the interior flakes. Fig. 2 is a nickel-steel bar (carbon 0.40 per cent.,

Jan 1, 1920

By C. W. Vaupell

THE Huitzuco mines lie in north central Guerrero, Mexico; production has been about 90,000 flasks of quicksilver since 1873. Near-surface ores fill extinct mud geysers and the deep deposits are chambered veins, stock-works in brecciated blocks, and replacements in limestone. The epigenetic minerals livingstonite, stibnite and sulphur occur in limestone, gypsum and dolomite through a developed vertical range of 260 meters. The deepest workings expose an increased amount of stibnite, which probably indicates that the lower limit of mercury mineralization is being approached. A resur-gence of heat and water formed geysers over an extended area after the period of mercury mineralization. Mud geysers, which are situated, in the outcrops, contain the secondary mercury minerals, cinnabar and barcenite in the gravel and mud filling the vents. A 150-ton flotation plant is in operation concentrating stope fills that assay 3.0 kg. of mercury per ton. In one open stope, which is more than one hectare in area and 60 m. high, 150,000 tons are available.

Jan 1, 1937

By Harry Morgan

ONE of the direct results of the increasing number of oil wells drilled to greater depths has been the development of new types of bits. These bits should resist the abrasive action of drilling and give the greatest footage before bit changes become necessary on account of dulled cutting edges. The loss of drilling time caused by changing bits becomes more important as the well becomes deeper, because the whole drill pipe must be unscrewed to make; each change. Under ordinary conditions the change takes: 2 1/2 hr. for round trip at 4000 ft., 3 hr. for round trip at 5000 ft., 4 hr. for round trip at 6000 ft., 5 hr. for round trip at 7000 ft. In other words, the time to change a stand of drill pipe (90 ft.) varies from 1 2/3 min. at 4000 ft. to 23 min. at 8000 ft. In general, the formation in the deeper zones is harder and dulls bits more quickly than the formations nearer the surface, therefore even a small increase of hole drilled per bit will decrease costs and increase speed of drilling.

Jan 1, 1929

By T. D. Tiemann

The extraction of iron oxide from several types of siliceous iron ore by digestion in sulfuric acid solutions was investigated in the temperature range from 80 to 258°F at concentrations from 10-60% H2SO4. Degree and rate of extraction were found to be critical with respect to both temperature and acid concentration, requiring temperatures in excess of 250° F and acid concentrations of 50% to effect 80-90% extraction of iron oxide in 60 min. Rate of extraction is directly related to surface area and apparently controlled by the rate of chemical reaction. The activation energy was found to be approximately 25,000 cal per g mol. Extraction characteristics of the several ores were found to be similar. The Department of Minerals and Metals Engineering at the University of Wisconsin conducts a continuing research program to develop processes for the utilization of low-grade iron ore deposits such as the nonmagnetic taconites of the Wisconsin Gogebic range. Methods under study include high-intensity magnetic and high-tension electrical concentration, flotation, direct reduction and chemical extraction. Concentration of a number of low-grade siliceous iron ores by the extraction of silica in sodium hydroxide solutions has been reported by the writer and others in the literature.1,2,3,4 Residual concentrates containing as much as 65% iron have been obtained from taconites containing less than 30%. Currently an alternative approach is under study, namely the dissolution of iron oxides from siliceous gangue by extraction in acid, with subsequent recovery of the iron from solution. Such a process for extracting iron oxide from the low-grade oclitic deposits of Alberta with hydrochloric acid was investigated and described by Gravenor, Govett and Rigg.5 The current investigation, which is entirely devoted to extraction with sulfuric acid, is the subject of this paper. In part, the objective of this research was to determine the possibility of leaching iron ores in situ with sulfuric acid. The investigation of a recovery method is left to later research. The ores investigated contained hematite (Fe2O3) as the principal iron-bearing mineral and minor amounts of goethite (Fe2O3 .H2O), magnetite (Fe3O4), and iron-bearing silicates. The gangue was essentially quartz occurring as single crystals and microcrystalline aggregates. Detailed description of the ores may be found in the literature.1,2,4,6 A comparison of the specific ores used in this investigation is shown in the partial analyses of Table I. EXPERIMENTAL METHODS All extractions were made at atmospheric pressure using beakers with a mechanical stirrer for those tests run below the boiling point, and Erlenmeyer flasks for those at the boiling point. A thermostatically controlled hot plate was used for heating, and this maintained the mean temperature within the solution to within ±3°F during extraction. The sample of ore for extraction was weighed to + 0.02 g. For tests below the boiling point, the sample was added to the beaker containing the sulfuric acid solution at the desired temperature. For the boiling-point tests, the sample was added to the Erlenmeyer flask followed by distilled water and the

Jan 1, 1968

By Luke L. Y. Chang, Bert Phillips

ThE tendency toward further oxidation of the intermediate oxides and the high volatilization rates of the higher oxides have prevented direct attainment of equilibrium data for the system tungsten-oxygen. As a result, St. Pierre et al.1 have proposed a phase diagram (to 800°C) based on thermody-namic data to 1200°C for the known tungsten oxides (WO2z, W18O49, W20O58, and WO3) and a report on a tungsten suboxide W3O.2 Recent modification of a technique previously described3 5 now permits adequate preservation of compositions of mixtures of metallic tungsten and metal oxides (e.g., of tungsten, cobalt, calcium, samarium, titanium) in order that condensed phase relations may be established to 1700 This method has been applied to study the high-temperature stability of tungsten oxides. In the method used, the desired compositions were sealed in nonreactive containers such that only a small gas volume remained. Each sample then established its own equilibrium atmosphere at temperature. This method has advantages in the study of systems of the W-0 type where knowledge of the condensed phases is desirable but for which composition and pressure of the gas phase are not readily attainable because of oxide volatility. Mixtures of 99.99 pct tungsten metal powder and purified tungsten anhydride (WO3) or in some cases W18O49* were equilibrated in pellet form in sealed

Jan 1, 1964

By Harry M. Mikami

Refractories are heat-resistant, generally nonmetallic materials used as the linings of furnaces or high temperature vessels in the steel, iron, nonferrous metals, glass, cement, lime, ceramic, chemical, petroleum, paper, and power and heat generation industries. Refractories must have structural strength at high temperatures but also, in many applications, must simultaneously resist chemical-physical corrosion-erosion from stags, metals, granular solids, or gases. Among the major uses are the pyrometallurgical processes for producing iron, steel, copper, aluminum, nickel, lead, zinc, etc. Rotary cement kilns, glass tanks, refineries, utility boilers, chemical and ceramic (including refractories) plants, and a myriad of other smaller scale users employ refractories in the high temperature parts of their operations. Thermal, chemical, and structural conditions under which refractories are used differ widely so there is a great variety of refractories to fill the various needs. Two major classifications are the "basic" and "acid" types. Basic refractories include magnesia and chromite, singly and in combinations, dolomite, and forsterite (olivine). The acid category includes aluminosilicates, alumina, and silica. There are a number of other specialized types such as carbon, graphite, silicon carbide, zircon, and zirconia that have important applications but are used in much smaller amounts than the major categories. Physically, refractories can be divided into bricks and shaped products on the one hand and unshaped or monolithic products (also termed specialties) on the other. There are many further subclassifications and divisions, a discussion of which is beyond the scope of this chapter; see Refs. 2 and 9. Raw materials for the principal basic refractories are magnesia and chrome ore. Magnesia, generally termed magnesite or periclase, is obtained mainly from seawater or saline brines extraction, but substantial amounts are produced from mined magnesite (MgCO3). Dolomite (CaCO3•MgCO3), another important basic refractory, is obtained entirely from mined sources. Acid refractory raw materials are: fire clays, flint clays, kaolin, and other natural clay minerals; aluminosilicate minerals such as kyanite, andalusite, sillimanite, pyrophyllite, bauxitic clays; calcined refractory grade bauxite, alumina from the Bayer process for the alumina group; and quartzitic rocks for silica refractories. The total value of all refractories shipped in the United States in 1974 was $989 million, a record to that date. Of this amount, about 73% represents bricks and shaped products and 27% is in nonshaped or monolithic products which comprise mortars, cements, castables, plastics, and ramming and gunning mixes. Fig. 15.4E.1 shows the rising value of all U.S. refractory shipments in the period 1948-1974. Values of brick and shapes paralleled

Jan 1, 1976

By Eugene H. Dawson

MICA is a mineral that once was a familiar sight as fireproof windows in stove and furnace doors and as lamp chimneys and shades. Since 1878, the beginning of the electrical age, the use of mica for such purposes has gradually declined and its use in electrical equipment and appliances has developed to such an extent that the known sources of supply are scarcely equal to the demand. With the increasing capacity of electric generating units, the size of mica sheets found in nature was inadequate. However, in 1894, a process was developed whereby thin films or splittings cemented with shellac or other binders could be pressed into large sheets. 18 The introduction of radio in the early 1920s created such a heavy demand for the smaller sizes of mica that on March 22, 1938, mica was included among 23 commodities on the list of strategic materials approved by the United States Army and Navy Munitions Board. To be included in this list, the material must be one whereof the domestic supply is not sufficient to meet the demand. COMPOSITION Mica is a complex mineral composed principally of the silicates of potassium, aluminum, and magnesium. Less prevalent species contain, as essential components, lithium, vanadium, and chromium. Iron usually is present either as an essential component or as an impurity. The mica group comprises some nine different species, five of which, muscovite, phlogopite, vermiculite, lepidolite, and biotite, are widely used in industry. Lepidolite and zinnwaldite (lithium micas) and roscoelite (vanadium mica) are sources of lithium and vanadium. Muscovite, "white mica," is potassium mica. Theoretical formulas H2KAl3(SiO4)3. There are two varieties, distinguished as to color, known in industry as ruby and green. In crystals or "books," the colors each range through varying shades of red and green. However, when split into thin films, all micas, except biotite and phlogopite, are colorless and transparent. Muscovite frequently is stained red or black by thin films of iron oxide between the laminae. The staining usually is derived from magnetite, which sometimes is found as unaltered crystals.

Jan 1, 1949

By F. C. Kelley, L. L. Wyman

In order to clarify and amplify the existing data concerning the action of the cementing material in cemented tungsten carbide alloys, the authors have initiated this investigation of the entire range of cobalt-tungsten carbide alloys. Inasmuch as the ultimate objective is relative to what actually goes on during the sintering of cemented tungsten carbide materials, this work was necessarily restricted to heat treatments similar to those used in actual production of these materials. In the course of numerous experiments, the authors have noted several conditions that indicated that there was a solubility to be considered. Among these factors are the following: 1. Many of the alloys showed a much larger amount of binding constituent to be present than could possibly be accounted for by the cobalt content. 2. In many areas, grains of the carbide constituent are much larger than the particles of carbide originally added. In addition, these grains are of very regular contour. 2a. In samples of cemented tungsten carbide which had been fused in the atomic hydrogen torch in the presence of excess binder constituent, immense grains are formed, and their shapes are very regular. This is also true when the cemented tungsten carbide of 13 per cent. Co content is fused alone in the atomic hydrogen torch. Contrary to general expectation, chemical analysis of this material, after fusion in the atomic hydrogen torch, checks the analysis of unfused material. 3. In making the cemented tungsten carbide materials by the process of exerting the pressure at the time of heating a certain portion of the &apos; contents squeezed out of the mold. Chemical analysis has shown that this material contains approximately 12 to 20 per cent. of tungsten. The microstructure shows a cored dendritic structure interlaced with eutectic network, and some graphite, as shown in Fig. 1. 4. Thermal analysis of these materials has consistently indicated an arrest point close to 1350" C.

Jan 1, 1931

E. A. Peretti (University of Notre Dame, Notre Dame, Ind.)—Mr. Deitz and Professor Halpern are to be congratulated on a fine piece of work which adds to our knowledge of precious metal—cyanide-solution reactions. I should like to offer the following comments: The authors state, "the rate plots were always linear, indicating a zero order reaction rate." This appears to conflict with the data of Fig. 6 which clearly show the rate to vary with the NaCN concentration. It seems to me that the rate curves are linear because of the experimental setup. The volume of solution is so large that over a three-hour period the change in NaCN concentration is very small. A rough calculation for the experiments of Table I where the initial NaCN strength was 0.0096 mol per liter show a change of NaCN concentration of about 0.0009 mol per liter at the end of three hours. In short, over the period of time that the experiment was in progress, the NaCN strength was practically constant; hence the rate of dissolution remained practically constant. Eq. 10, as written, specifies that 1 mol of H202 and 2 mol of hydroxyl ion are formed when 2 mol of silver react. Is this true? The effect of H,O2 on the rate was made in solutions having an oxygen pressure of 4.8 atm. Were any tests made in solutions containing hydrogen peroxide, but no oxygen? G. M. Willis (University of Melbourne, Melbourne, Australia)—The authors have shown that, under their experimental conditions of high O2 concentrations, the rate of solution of silver in aqueous cyanide solutions is controlled by diffusion of O2 or CN- to the metal surface. With diffusion control, it is generally not possible to obtain further information about the mechanism of a process.

Jan 1, 1955

By C. A. Hartnagel, D. H. Newland

Most of the petroleum produced in New York State is obtained by flooding; that is, water drive. No important oil fields have been developed during the past 30 years, nor does there seem much hope that the productive oil areas will be substantially enlarged in the future. There is some prospect that additional supplies may be obtained by deeper drilling, but deep tests for gas to the Oriskany sandstone in some of the oil-producing areas have been without results so far as any discoveries of oil are concerned. Although the flooding method had been made legal in 1919, and some floods had been in operation previous to 1921, that year marks the beginning of a rapid increase in oil production by the new method. The flush production of oil in New York was in 1882, shortly after the discovery of the Richburg pool in Allegany County. The oil production in that year amounted to 6,685,000 bbl. The 1937 production of 5,478,000 bbl. was the largest since the flush production of 55 years ago. The effectiveness of water-flooding for increasing oil production from the old New York fields is shown in Table 1. Table 1.—Production of Oil in New York since 1921 Year Barrels Year Barrela 1921 988,000 1929 3,377,000 1922 1,000,000 1930 3,647,000 1923 1,250,000 1931 3,363,000 1924 1,440,000 1932 3,508,000 1925 1,695,000 1933 3,181,000 1926 2,242,000 1934 3,804,000 1927 2,603,000 1935 4,236,000 1928 3,377,000 1936 4,633,000 1937 5,478,000 The area of the New York oil fields is about 60,000 acres. It has been estimated that not over one-fourth of the area is being flooded. Very little of flooded territory has ceased to produce. Some leases flooded by the early, less scientific methods are being again subjected to the water

Jan 1, 1938

By K. A. Jackson, J. D. Hunt

A general theory for the growth of lamellar and rod eutectics is presented. These modes of growth depend on the interplay between the diffusion required for phase separation and the formation of interphase boundaries. The present analysis of these factors provides a justification for earlier approximate theovies. The conditions for stability of rod and Lanlellar structures are consitleved in terms of the mechanisms by which the structure can change. The mechanisms considered include both small adjustments to the lnnzellar spacing due to the motion of lamellar faults, and catastrophic changes due to instabilities. It is concluded that stable growth occurs at or near the minimum interface undevcooling for a gizierz growth rate. The conseqrlences of the existence of a diffusion boundary layer at the interface are discussed. The experimental results for the variation of growth rate, undercooling, and Lanzellar spacing are cornpared with the theory. We believe that the theory presented in this paper provides an adequate basis for understanding the complex phenomena of lanzellar and rod eutectic growth. The growth of lamellar eutectics has been the subject of several theoretical and many experimental studies. The foundations for the theoretical work were laid by zenerl and Brandt2 in their analyses of the growth of pearlite. Zener estimated the effect cf diffusion, and took into account the surface energy of the lamellar structure. He found that the lamellar structure could grow in a range of growth rates at a given undercooling provided the lamellar spacing was appropriate for the growth rate. Since pearlite grows with only one growth rate and one lamellar spacing at a given undercooling, there is clearly an ambiguity in the theory. Zener removed this ambiguity by postulating that the growth rate was the maximum possible at the given undercooling. He predicted then that the product of the growth velocity v and the square of the lamellar spacing A should be constant, i.e., A2v = const. Brandt2 started out by assuming that the interface between the lamellae and austenite was sinusoidal. Because of this, the ambiguity encountered by Zener did not arise. Brandt was able to obtain an approximate solution to the diffusion equation, but, since he did not take into account the surface energy, his considerations are incomplete. Tiller3 applied some of these ideas to the growth of eutectics, and proposed a minimum undercooling condition to replace the maximum velocity condition used by Zener. These conditions are formally identical. Hillert4 extended the work of Zener. He found a solution to the diffusion equation assuming the interface to be plane. Taking surface energy into account, and applying Zener&apos;s maximum condition, he was able to calculate an approximate shape of the interface. Jackson et al.5 used an iterative method employing an electric analog to the diffusion problem to refine the calculation of interface shape. It was found that the interface shape calculated from a plane-interface solution to the diffusion equation was negligibly different from the exact solution. The method provided an analog only for eutectics for which the volumes of the two phases are equal, growing from a melt of exactly eu-tectic composition. There has also been considerable experimental work on eutectics, Several experimenters8-10 found that A2v is constant as predicted by Zener.1 Hunt and chilton10 demonstrated that ?T/v1/2 is also a constant for the Pb-Sn system as predicted. Lemkey et al.11have recently found A2v to be constant for a rod eutectic. In the present paper, we present the steady-state solution for the diffusion equation for a lamellar eutectic growing with a plane interface, for the general case, that is, with no restriction on the relative volumes of the two phases, and with the melt on or off eutectic composition. A similar solution is also found for a rod-type eutectic. Expressions are obtained for the average composition at the interface and the average curvature of the interface. These equations for the average composition and curvature are similar in form to those derived by Zener1 and Tiller,3 and provide a justification for some of the approximations made by these authors. The mechanisms by which the spacing in a lamellar structure can change are considered. The important mechanism for small changes in lamellar spacing involves a lamellar fault. Examination of the stability of lamellar faults leads to the conclusion that the growth occurs at or near the extremum.* The insta- bilities which can develop in a rodlike structure are also discussed, resulting in the conclusion that this structure also grows at or near the extremum. Comparison of the conditions for rod and lamellar growth permits a prediction of the surface-energy anisotropy required to produce rods or lamellae for various volume-fraction ratios. The diffusion equation predicts the existence of a diffusion boundary layer at the eutectic interface unless the eutectic has 0.5 volume fraction of each phase and is growing into a liquid of eutectic composition. This boundary layer is such as to make the composition in the liquid at the interface approximately equal to the eutectic composition. This boundary layer permits changes in composition during the zone refining of eutectics. Photographs of the eutectic interface of a growing transparent organic eutectic system have been made. Both the components of this eutectic are transparent organic compounds that freeze as metals do.12 The in-

Jan 1, 1967

By R. Maddin, A. Lawley

Single crystal Mo-Re alloys (99.99+ purity), grown by electron bombardment floating zone heating, were deformed in tension at temperatures from -196° to +200°C. At -196oC, Mo-6 pet Re and Mo-20 pct Re alloys deform by slip on systems of the type (101) [1ll]. Above-78oC, the operative slip system is of the type (112) [111], (101) [1ll], or (211) [1ll], depending upon orientation. Mo-39 pct Re alloys deform by twinning and slip at all test temperatures with a (112) [111] type twinning system. Critical resolved shear stress for slip and twinning is calculated as a function of composition and temperature, and the mechanical properties compared with those of less Pure polycrystalline alloys. HEXAGONAL close-packed rhenium, c/a = 1.615, is highly soluble in molybdenum. The bee molybdenum-rich solid solution extends to approximately 42 at. pet Re* at 2500°C,&apos; Fig. 1. Recent work on polycrystalline alloys has shown conclusively that the addition of rhenium to molybdenum improves both the fabricability and the low-temperature ductility.2"5 Similar behavior is observed for W-Re and Cr-Re alloys.5 Initially, Geach and Hughes2 found that the Mo-30 pct Re alloy could be cold rolled to approximately 90 pct reduction before the onset of cracking. The remarkable effect of the rhenium was later confirmed by Jaffee et al. 3-5 with an optimum condition of maximum strength combined with maximum ductility at the Mo-35 pet composition. At higher rhenium contents, the ductility was severely impaired due apparently to the presence of brittle tetragonal s phase, Fig. 1. In the Mo-35 pet Re alloy, at least 110 ppm (parts per million) oxygen could be tolerated before cold workability was reduced. By comparison, the corresponding tolerance figure in unalloyed molybdenum is ~ 10 ppm. The effect of rhenium was considered in terms of: 1) a reduction in oxygen solubility in the lattice; 2) a redistribution of intergranular oxide from grain boundary films to isolated spheres; and 3) the promotion of twinning as a further mode of plastic deformation. Paradoxically, twinning is often associated with brittle fracture in iron and the silicon irons.6&apos;7 Work to date has been restricted to are-melted and powder metallurgy polycrystalline material of ~ 99.9 pet purity. The present investigation was initiated for the purpose of determining the mode and crystallography of plastic deformation of a series of bee Mo-Re alloy single crystals over a wide temperature range from -196o to +200°C. Using high-purity zone-melted material (~ 99.99 + pet purity), the specific role of rhenium in the molybdenum lattice may be understood more fully since effects due to grain boundaries and oxide redistribution will be absent. At the same time, the study provides a comparison of single and polycrystalline deformation behavior. EXPERIMENTAL TECHNIQUES A) Preparation and Purity of Single Crystals. Alloys in the form of either are-cast and swaged or sintered and ground bar, 0.120 in. diam, were obtained from the Chase Brass and Copper Co. Alloy single crystals ~ 8-in. long were grown from the

Jan 1, 1962

By D. J. Dunn, J. L. Huiatt, T. E. Norman

Corrosion studies in laboratory ball mills and grinding environment simulations produce corrision rates and total metal removal rates much lower than those recorded in operating production ball mills. The corrosion component of ball metal loss in many mills probably represents less than 10% of the total loss, judging from AMAX experience and recent US Bureau of Mines (USBM) tests. Such small absolute losses are consistent with ball metal loss measured in production ball mill marked ball wear tests to determine effects of corrosion and abrasion resisting properties of alloys in operating mills. These indicate that metal hardness and microstructure determine relative metal loss rates of a given situation. The combination of ore characteristics and grinding process dynamics determine metal loss severity. Alloying for corrosion resistance and modification of the milling corrosion environment yield relatively small metal loss reductions. Alloying and heat treatment to produce high hardness and microstructures of high carbon martensite and, for cast irons M7C3 carbides, produces the lowest metal losses in typical wet grinding applications.

Jan 1, 1986

ENROLLMENT of both undergraduate and graduate mineral engineering students rose approximately 11.8 pct over last year to a total of 12,830. Leading again in the enrollment climb was ceramic engineering which increased by about 21 pct. Approximated increases in enrollment of the other mineral engineering categories, in order, were: metallurgical 17.7 pct; petroleum 13.3 pct; geological and geophysical 3.3 pct: and mining proper, the lowest with 2.9 pct. Total ECPD school enrollment climbed to 242,405 -just below the 1947 peak, but 14.4 pct higher than 1955. Engineering enrollments have shown a general increase since 1951, and freshmen enrollments have climbed steadily since 1950.

Jan 5, 1957

By J. T. McGrath, G. B. Craig

Tensile tests on aluminum single crystals, grown from the melt, revealed that the yield stress of these crystals was raised as the amount of striation substructure was increased. The number of striation-type boundaries was varied by changing the rate of growth of the crystals. The results are interpreted in terns of a blockage of dislocation movement by striation boundaries. IMPERFECTIONS are known to have a large effect on the mechanical properties of metals. Teghtsoonian and Chalmers 1 studied a block or striation-type substructure in tin and found that the formation of the striations depended upon rate of crystal growth and orientation. They found that the angular misorienta-tion between neighboring striations varied between 15 min and 5 deg. Atwater and chalmers2 investigated striations in tin and lead, and found that purity was another factor which influenced their formation. There was a limiting purity above which the striations were straight and regular. There is little information in the literature concerning how substructures in melt-grown crystals affect strength. washburn3 introduced small-angle boundaries into zinc by a shear process and found a subsequent increase in yield stress which he attributed to the presence of these boundaries. Lauriente and pond4 found the critical resolved shear stress in aluminium crystals grown from the melt, to increase with etch pit density. The etch pits were used as an indication of growth imperfections. In Hibbard&apos;s5 work on lineage structure in copper crystals grown from the melt, he tested one crystal containing interlineage boundaries, and found a 50 pct increase in the critical resolved shear stress. Fleischer and Chalmers6, in a recent paper, mention briefly that, in the production of aluminium crystals from the melt when the growth rate was raised from 1.2 to 18 cm per hr, the yield stress increased 50 pct. They felt that the increase in yield stress with rate of growth might be attributed to a higher concentration of impurities in the gage length and also might be affected by the increased number of small-angle boundaries (striations). The present investigation was undertaken to determine the effect of the striation substructure on the strength of aluminum single crystals. EXPERIMENTAL PROCEDURE Aluminum single crystals of 99.9992 purity were grown from the melt using a technique described by Chalmers.7 The growth rate was varied from 0.6 to 20 mm per min, thus producing crystals with varying numbers of striation boundaries. To avoid prior deformation, the crystals were chemically cut to the desired length with a saturated solution of cupric chloride. They were then annealed at 580°C for 24 hr and allowed to cool slowly in the furnace. Finally, the specimens were electropolished using an electrolyte of 5 parts ethyl alcohol and 1 part perchloric acid. Each specimen was approximately 5 in. in length and 0.125 sq in. in cross section. The average orientations of the 5 series of crystals studied are shown on the stereographic projection of Fig. 1. The crystals were strained approximately 2 pct in a soft tensile machine. The strain sensitivity was 3.6 x 10-4 cm over a 5-cm gage length.

Jan 1, 1960

By R. F. Mehl, C. S. Barrett, A. H. Geisler

THE studies of the mechanism of precipitation and of the resulting property changes in aluminum-silver alloys1-3 have presented some new concepts of the aging reaction-concepts that may be fundamental in establishing a complete quantitative theory of age-hardening. With both aluminum-copper and aluminum-silver alloys, thin platelike aggregates form parallel to the Widmanstätten planes of precipitation.1,4 These platelets grow in lateral dimensions and in thickness with aging time until they are thick enough to produce an X-ray diffraction line pattern. Their structure is that of a transition lattice which is coherent with the matrix, since the atomic spacings in the matrix and the precipitate are the same on each side of their common interface.2,4 The equilibrium precipitate forms later from and at the expense of the transition lattice. Since age-hardening occurs during the formation and growth of the transition lattice, the major contributor to the hardening no doubt is the stress condition in the matrix resulting from the matrix holding the precipitate in the coherent condition. The development of these stresses also appears to be responsible for an increase in the electrical resistance superimposed on the normal decrease resulting from a change in the concentration of the matrix during aging.3 The two consecutive reactions constituting the aging process are accompanied by characteristic microstructural alterations. The initial precipitation process results in the formation of a Widmanstätten figure, while the later transformation of the transition lattice to the equilibrium lattice is accompanied by a coalescence, in the case of aluminum-copper alloys,5 and by the appearance of light areas at the grain boundaries with aluminum-silver alloys showing a structural rearrangement of matrix and precipitate.3 This latter reaction is similar microscopically to the so-called "discontinuous precipitation." Possibly discontinuous precipitation is a process that often if not always follows true precipitation of a coherent lattice and during which the transformation of the coherent transition lattice to the equilibrium lattice takes place accompanied by matrix recrystallization.3 EXPERIMENTAL PROCEDURE The alloys were made using 99.97 per cent Al or distilled magnesium, with

Jan 1, 1943

By B. W. Roberts, V. A. Phillips

A copper alloy containing- 25.5 at, pct Zn and 19.0 at. pct Ni, which was previously found to show an anoma1old.s hardening effect on quenching- from 600 "C and aging- at 400oc, has now been examined by neutron diffraction. No evidence of long-range order was found. The aged sample showed diffuse scattering- consistent with clustering. The anomalous hardening effect is now attributed to lattice strains caused by clustering rather than (long-range) order hardening. SOLID-solution Cu-Ni-Zn alloys (the commercial &apos;nickel silvers") have been reported to show anomalies in: change of resistivity on cold working,1-6 temperature coefficient of resistance,2-12 resistivity at low temperatures,13,14 parameter (vs temperature),2"4 calorimetric data,2,4 specific heat,15,16 dilation,2-4 and elastic modulus.17 The structure responsible for the anomalies is produced by annealing typically near 400°C and is rather loosely referred to as the (&apos;K-Zustands" (K state), a term coined by Thomas1&apos; who apparently meant simply that the arrangement of atoms on the sites deviated from that expected statistically. Thomas proposed that the K state occurred in a variety of (solid-solution) alloys such as Cu-Ni-Zn, Ni-Cr, Ni-A1, Ni-Cu, Fe-A1, and Fe-Si and is recognized because its formation is strongly temperature-dependent and results in an increase in electrical resistance which can then be decreased by cold working. Later workers on (&apos;nickel silver" have interpreted the K state variously as short-range order, long-range order. or a combination. The present work was prompted by the discovery by Phillips and Jones19 of a substantial hardening effect when an 18 pct "nickel silver" alloy which is fairly close to the Cu2NiZn composition, was reheated in the range 150" to 450 C after previously quenching from 600°C or, alternatively. was slow-cooled from 600°C or above. The phenomenon was attributed to (long-range) order hardening. Due to the similarity in the atomic scattering factors of copper. nickel, and zinc atoms, the &apos;&apos;nickel silvers" are unfavorable for X-ray diffraction studies aimed at detecting ordering. Nevertheless Bialas et a1.,20 using a powder sample containing 47.96 wt pct Cu, 24.03 wt pct Ni, and 27.98 wt pct Zn, slow-cooled from 400" to 200°C taking 500 hr, observed weak super lattice lines. Further unpublished work" using an anomalous dispersion X-ray technique indicates that zinc atoms are regularly ordered at the corner points of the lattice cell, while the nickel and copper atoms are statistically distributed on the remaining sites. Köster 17 also observed X-ray superlattice lines, for example, in an alloy containing 43.5 wt pct Cu, 28.6 wt pct Ni, and 27.9 wt pct Zn superimposed on the basic fcc cell with a = 3.62 kX. He proposed a Cu3Au-type superlattice with the Ll2 structure in which the A sites were statistically occupied by copper and nickel atoms and the B sites by zinc. He adds that substitution must be possible so that zinc atoms partly occupy A sites. Below about 35 pct Cu, Koster had some evidence for a CuAu-type superlattice with the Llo tetragonal fcc structure with a = 3.82 kX, c/a = 0.88 which could be preserved by quenching. This is suggested17722 to correspond to CuNiZn. While the present work was in progress Hirabaya-shi et a1.23 made an independent comprehensive neutron-diffraction study of a single crystal containing 50.05 at. pct Cu, 26.57 at. pct Ni, 0.25 at. pct Mn, 0.13 at. pct Fe, balance zinc. The presence of manganese and iron is surprising since the crystal was supposedly grown from high-purity metals. The homogenized crystal showed evidence of long-range ordering after an anneal of 5 months at about 300°C. Three possible crystal models were proposed. A curious feature of their results23 is that they could not find any neutron-diffraction evidence of ordering in a powdered polycrystalline near-stoichiometric Cu2NiZn alloy. There appears to be some essential difference between a near-stoichiometric Cu2NiZn alloy and one somewhat further off stoichiometry as used by the present authors. Thus Sato14 was able to reproduce the low-temperature resistivity anomaly reported by one of the authors13 on the present alloy if he used a similar composition, but found the normal behavior of the residual resistivity in a near-stoichiometric alloy. satol2 found that the resistivity of a cold-drawn slightly off-stoichiometric alloy increased to a maximum on isothermally annealing at 300°C and then decreased ("over-aged"). Since he could not explain this on the basis of ordering phenomenon, he proposed that zinc atoms were segregating to stacking faults (Suzuki effect) and found etching bands on the surface by replication which were attributed to the widening of faults. Sato suggested14 that the hardening effect observed by Phillips and Jones19 is partly due to the Suzuki effect. EXPERIMENTAL The starting material was 1/4-in.-diam hard-drawn rod of a commercial 18 pct "nickel silver" alloy identical with that used in a previous study by Phillips

Jan 1, 1967

Capable of processing 3500 tpd of uranium ore, the United Nuclear-Homestake Partners&apos; mill in Grants, N. M., differs considerably from the nearby mills of Anaconda and Kerr-McGee in at least two major aspects: it leaches uranium ore with an alkaline solution of Na2C03 and NaHC03 instead of sulfuric acid; and it recovers yellowcake directly by precipitation from the pregnant alkaline leach solution, without any need of ion exchange or solvent extraction circuits. A first look at the flowsheet shows that this mill has two separate grinding and leaching circuits. Reason for the double circuitry: the mill treats, on a toll basis, uranium ores for Anaconda as well as for the partnership, and it must also treat ores coming from mines separately owned by Homestake Mining Corp. and from mines owned by United Nuclear Corp.

Jan 8, 1974

By L. L. Wyman

IN order to clarify and amplify the existing data concerning the action of the cementing material in cemented tungsten carbide alloys, the authors have initiated this investigation of the entire range of cobalt-tungsten carbide alloys. Inasmuch as the ultimate objective is relative to what actually goes on during the sintering of cemented tungsten carbide materials, this work was necessarily restricted to heat treatments similar to those used in actual production of these materials. In the course of numerous experiments, the authors have noted several conditions that indicated that there was a solubility to be considered. Among these factors are the following: 1. Many of the alloys showed a much larger amount of binding constituent to be present than could possibly be accounted for by the cobalt content. 2. In many areas, grains of the carbide constituent are much larger than the particles of carbide originally added. In addition, these grains are of very regular contour. 2a. In samples of cemented tungsten carbide which had been fused in the atomic hydrogen torch in the presence of excess hinder constituent, immense grains are formed, and their shapes are very regular. This is also true when the cemented tungsten carbide of 13 per cent. Co content is fused alone in the atomic hydrogen torch. Contrary to general expectation, chemical analysis of this material, after fusion in the atomic hydrogen torch, checks the analysis of unfused material. 3. In making the cemented tungsten carbide materials by the process of exerting the pressure at the time of heating a certain portion of the contents squeezed out of the mold. Chemical analysis has shown that this material contains approximately 12 to 20 per cent. of tungsten. The microstructure shows a cored dendritic structure interlaced with eutectic network, and some graphite, as shown in Fig. 1. 4. Thermal analysis of these materials has consistently indicated an arrest point close to 1350° C.

Jan 1, 1930