Search Documents

By D. H. Gurinsky, D. G. Schweitzer

The empirical equilibrium constantsd the heat of reaction for the reduction have been determined from 300° to 500°C. The mechanisms of the oxidation of uranium and magnesium from dilute bismuth solutions have been investigated. The kinetics of some of the reactions were affected by air adsorbed on the uranium oxides. THE Liquid Metal Fuel Reactor studied at Brook-haven National Laboratory uses a solution of uranium in bismuth as the fuel. Corrosion and stability problems require that the fuel solution contain corrosion inhibitors and deoxidants. Of the additives tested, magnesium has been found to be the best deoxidant and zirconium the best corrosion inhibitor in bismuth. Some experiments1 indicate that magnesium may play a secondary role in increasing the effectiveness of zirconium in inhibiting corrosion. The work reported here was intended to determine the relative concentrations of Mg and U required to prevent oxidation of the uranium fuel in the event of an air leak. In addition, an attempt was made to identify some of the mechanisms of the oxidation and reduction reactions occurring in the liquid bismuth solutions. EXPERIMENTAL Apparatus and Procedure—The equipment shown in Fig. 1 was designed so that the reaction kinetics could be studied as functions of temperature, melt composition, pressure, and flow rate. At the start of a run, the 10-liter bell jar (F) is removed by opening the bottom Dresser fitting (L), and the bismuth and additives are placed in a pyrex crystallizing dish (I). The bell jar is replaced, the system is evacuated to 10-5 to 10-6 mm Hg and then the heater (J) is turned on. When the selected temperature is reached, the oxidizing gas is admitted to the system to the desired pressure as read on the manometer (D). Gas is introduced through the slide tube (Q) which has a pyrex frit (R) sealed to its bottom. Stirring is accomplished by immersing the end of the tube in the melt. To maintain a constant pressure under flow the input and evacuation rates must be equalized. To obtain this condition stopcock (C) is closed and flowmeters (B) are matched. The reaction is "stopped" by closing the inlet flowmeter and quickly evacuating the system. To obtain a liquid metal sample, the system is evacuated with the sampler positioned near the surface of the liquid. The sampler, Fig. 2, is then immersed until its thermocouple reading matches thermocouple (G) Fig. 1. The system is then pressurized with helium which forces the solution through the frit. Twenty to 30 min elapsed between the time the system was evacuated and sampled. During evacuation and pressurization of the system, the temperature variations did not exceed ± 5°C. While bubbling occurred the temperature remained constant to within 1/2 oC. The volume of the equipment was determined by adding a known volume of air at atmospheric pressure to the evacuated system and noting the resulting pressure.

Jan 1, 1962

By A. T. Miesch

The purpose of this paper is to explore relations between the distribution and composition of uranium deposits on the Colorado Plateau and mineralogic, chemical, and lithologic aspects of their host rocks. The paper also appraises the host-rock sandstones as possible sources of elements in the uranium deposits. Other possible sources of elements are not discussed. Uranium deposits on the Colorado Plateau consist largely of sandstone and small amounts of mud-stone impregnated with uranium and vanadium miner- als and a suite of minor accessory minerals containing copper, lead, zinc, silver, iron, cobalt, nickel, yttrium, molybdenum, selenium, and arsenic, in addition to other elements locally. The deposits consist of clusters of closely spaced ore bodies which commonly aggregate several thousand tons, but range in size from less than one ton to several million tons. With only rare exception, the deposits show no close relation to fractures. The ore bodies are generally tabular in layers nearly parallel to the bedding in the host rocks, or they cross bedding at large angles to form roll structures. Absence of fracture control necessitates that the ore and associated elements were transported to the deposits by way of interstitial pore spaces in the sandstones. This points to the general process of lateral secretion as a possible mechanism of ore formation, and suggests the host-rock sandstones as a possible source of the metals. Roll structures in the ore

Jan 1, 1962

By R. P. O’Shea

AS part of a program to investigate phase relationships in ternary systems containing semiconducting elements and compounds, an X-ray survey of alloys in the system Pb-Te-Bi was carried out which revealed that the pair PbTe-Bi probably formed a quasibinary system. This portion of the ternary was examined fully by thermal analysis, X-ray, and microscopic procedures. More than twenty-five alloys were made by melting together the proper combinations of the elements in quartz tubes at a temperature of 1000o C. The compositions which were high in PbTe content were prepared in evacuated, sealed, quartz tubes, allowed to freeze in vacuum, and then transferred to Crucibles for thermal analysis. The bismuth-rich alloys were made directly in the crucibles under a protective gas cover. The starting elements were obtained from the American Smelting and Refining Co. and had a purity greater than 99.99 pct. Cooling curves were made with about 50 g of alloy in graphite crucibles which were placed in a covered quartz container in which a protective atmosphere of helium or nitrogen was maintained. The thermocouple protection tube was made of mul-lite and served as a stirring rod when connected to a reciprocating stirring motor. Temperatures were

Jan 1, 1962

By C. B. Smith, A. G. Guy

The power and convenience of tensor analysis are employed in deriving the equations that describe three-dimensional diffusion in an n-component system plus vacancies. A "Kirkendall coordinate system, '' defined in principle by Kirkendall markers, is used in defining the intrinsic diffusion coefficients that are of primary interest. The defining equations are then transformed to local cartesian coordinates and to fixed cartesian coordinates, the latter being convenient for experimental measurements. Finally, it is shown how the intrinsic diffusion coefficients can be calculated from the experimentally determined quantities. It is generally recognized that any treatment of the essential diffusion phenomena in metallic systems—the jumping of atoms from one lattice position to another—must be based on movement of the atoms past Kirkendall interfaces.' A logical extension of this idea is the proposal that, fundamentally, diffusion must be described mathematically in terms of "Kirkendall coordinates." The basic equations thus obtained may then be transformed into other coordinate systems, when such transformation leads to simplification of either the experimental or mathematical treatment of diffusion data. Tensor analysis is clearly the appropriate mathematical tool for this purpose, since it provides methods both for determining general equations that are valid for all coordinate systems and for conveniently transforming the equations from one coordinate system to another system related to the first in some known fashion. For the present purpose three coordinate systems are used, and it is convenient to begin with a description of the relations among these three systems. FICK LAW FOR KIRKENDALL COORDINATES The reference coordinate system, and the one that is useful for most experimental measurements, is a cartesian coordinate system, xi (i = 1, 2, 3), fixed with respect to some point in the specimen, such as an end of the alloy bar undergoing diffusion. A second set of coordinates, the Kirkendall coordinate system, is one that in principle can be described by the location of inert markers (Kirkendall interfaces). A convenient mathematical relation between Kirkendall coordinates, x'i, and the reference cartesian coordinates, ii, is obtained by specifying that the Kirkendall coordinate system coincide with the cartesian system at time, t = 0. After diffusion has occurred for some time, t = t, the Kirkendall coordinate system will differ from the reference system in the manner shown schematically for the one-dimensional case in Fig. 1. The third coordinate system is Darken's1 local cartesian-coordinate system, xi, which is identical with ii in orientation and units, but which moves with the point under consideration in the Kirkendall coordinate system. Even though most diffusion problems are essentially one-dimensional, there is an advantage in first carrying out the analysis of the three-dimensional problem to gain a clearer insight into the assumptions that are made in the usual one-dimen-

Jan 1, 1962

By R. G. McQueen, E. G. Zukas

THE production of isotropic fine-grained ingot iron would be most useful since physical measurements associated with the elastic properties of iron are influenced by the size and orientation of the individual grains. This can be accomplished at present for small samples by established metallurgical procedures, but for large samples (in excess of 2 in. diam by 1 in. thick) it is virtually impossible to produce reasonably small uniform grains with random orientation. Such pieces can, however, be produced by impulsive loading followed by a suitable recrystallization treatment. The shock loading system employed is diagrammed in Fig. l. Here the 3/8-in. iron plate is accelerated by the plane-wave initiated high explosive charge through a 1 5/8-in. air space. Collision of this plate and the specimen of interest generates a shock wave in excess of 300 kbars which passes through the specimen. For this type of work it is not necessary to use machined parts: for example, the ingot iron pieces are saw cut from the billet so that they can be inserted in short sections of iron pipe. The recovered specimens are less distorted, however, if the air gap between the iron sample and pipe is filled with Woods metal. The dimensional changes resulting from this type of loading technique are minor, usually less than a 10 pct reduction in thickness. Compressive yield

Jan 1, 1962

By Gerd L. Klinkenborg

Ever see a curvaceous conveyor belt? Reports from Europe indicate appreciable interest in a relatively new system that has revamped some of the concepts of what single-belt conveyors can and cannot do. Invented about ten years ago by two German engineers, the so-called "Serpentix" single-belt conveyor, patented by the firm of Albert Stuebbe, is now operating at more than 100 foreign installations. The system boasts of three unique capabilities-climbing, turning and side discharge of load-which give it, the advantages of a multiple-unit system. The new conveyor needs only one drive station (which may be combined with tensioning), and except for the immediate area of the drive, is capable of conveying loads over a non-linear route. Transfer points are eliminated, and discharge points, which may be located anywhere along the route, may be operated automatically or manually, by direct or remote control.

Jan 1, 1962

By Paul A. Farrar, Felix Ermains, Harold Margolin

The systems Ti-Crand Ti-Vhave been reinvesti-gated in the region up to 40 wt pct alloying addition using both conventional and rapid quenching techniques. The Ti-Cr eutectoid temperature was determined to be at 667° & 10° C and 14.5 wt pct Cr. The solubility of the Cr in a Ti was found to be less than 1 pctat 700"C. The P transus of the Ti-V system was found to be depressed to 510°C at 40 wt pct V and the solubility of V in a Ti was found to be less than 2 wt pct at 700°C. Investigation by a. d. McQuillan1-3and m. k. McQuillan4 on the systems Ti-Co, Ti-Cr, Ti-Cu, Ti-Fe, Ti-Mn, Ti-Ni, and Ti-V has cast doubt as to the position of the ß/a + ß boundaries in many of these systems. Their investigations were carried out using hydrogen pressure and/or rapid quenching experiments, as opposed to the conventional quartz capsule techniques employed by most other investigator.'" By these methods, the ß/a + ß boundary was found to be lower than that obtained by conventional techniques in all except the Ti-Fe system. In the latter, the ß/a + ß boundary was essentially the same as the boundary obtained by conventional technique.7' On the basis of rapid quenching results in the Ti-Cr system, M. K. McQuillan4 placed the eutectoid temperature below 550°C whereas other investigations using conventional techniques had placed the eutectoid variously as between 650' and 700°C,5 between 675' and 700°C,6 between 650" and 675°C,7 at 670°C,8 and above 625"C.la9l3 In order to check these results, a reinvestigation of four of the systems was undertaken using both conventional and rapid-quenching techniques. The Ti-Fe and Ti-Mn systems will be dealt with in anoth er paper, with only the Ti-Cr and Ti-V systems being discussed here. EXPERIMENTAL TECHNIQUES Alloys employed for the delineation of the systems under investigation were prepared from iodide titanium sheet capsules containing the alloying materials,

Jan 1, 1962

By N. A. Tiner

A study was made of the effects of temperature, type of loading, and electric polarization on the fracturing behavior of copper and zinc coated with mercury. Copper showed an em-brittlement only in cyclic loading, whereas zinc showed an em-brittlenzent in both static and cyclic loading. The embrittle-ment of zinc in static loading was prevented by sub-zero cooling to a temperatzcre of about -70°F. The emhrittlement of both metals was sliglztly reduced by cathodic polarization of mercury. The basic processes involved in fracturing were discussed in the light of these observations. When a solid metal is in contact with certain liquid metals possessing high wetting characteristics, a weakening effect is produced, and the solid metal fractures in brittle manner at a relatively low stress. This lowering of the fracture stress generally is considered different from the stress cracking caused by a corrosive liquid environment and is attributed to the lowering of the solid-liquid interface tension at the grain boundaries.1-4 The purpose of this paper is to describe a number of observations on the special features of fracturing of copper and zinc coated with a liquid mercury film, and to analyze the basic processes involved in fracturing in the light of these observations. EXPERIMENTAL OBSERVATIONS I) Effect of Type of Loading—The evidence appears to indicate that in static loading, metals usually fracture by the initiation of microcracks in the interior preferentially at the grain boundaries or at the intersection of slip bands.' In cyclic loading, cracks develop on the surface within the active slip zones, and gradually propagate with increasing num- ber of cycles.6'7 Because of this difference in the manner of initiation of cracks, a series of bare and mercury coated copper and zinc specimens was subjected to static and cyclic loading, and their fracturing behavior was examined. The specimens were machined to 0.25 in. in diam and 1 in. in length from a high-purity commercial bar stock, and annealed at an appropriate temperature. Mercury was applied to the surface of the specimens by rubbing with cotton wool soaked in a saturated solution of HgCl2 or by etching with a dilute solution of HC1 and rubbing with purified mercury and by washing in water. The static tension load-extension curves were obtained by means of a Riele Screw Power Universal Testing Machine. The room-temperature load-extension curves for copper and zinc are shown in Fig. 1. The deformation behavior of copper, as judged from the general configuration of the load-extension curve, was not affected by mercury coating. The maximum load to fracture and the elongation at the maximum load were practically the same for both specimens. The mercury coated copper, however, showed somewhat less localized necking and had smaller reduction of area than the uncoated metal. The behavior of mercury coated zinc was radically different from the behavior of uncoated metal. The load-extension curves were the same at the

Jan 1, 1962

By Jr. W. L . Phillips

The deformation and fracture characteristics of lithium-fluoride single crystals stressed in compression at room temperature have been studied. In as-cleaved specimens the stress-strain curves were variable; two types of {110} fractures were observed in the vicinity of kink bands. The stress-strain curves of annealed crystals were reproducible; {100} cracks formed which propagated along the (100) and (110) planes. The deformation and fracture characteristics were affected by quenching and X-ray irradiation. STUDY of the mechanical behavior of nonmetallic materials has received considerable impetus in recent years because of the need to overcome the problem of brittleness before the refractory properties of nonmetallics can be fully exploited. Ionic crystals provide a convenient and simplified starting point from which to study the deformation and fracture processes in nonmetallic materials. Early investigations of the mechanical behavior of non-metals were restricted largely to determinations of the crystallographic indices of the cleavage and fracture planes and the glide and twinning elements. Until recently, only occasional systematic studies of the deformation characteristics of non-metals have been made; and investigations of the forces necessary to initiate plastic deformation and the factors which affect the flow characteristics have been restricted largely to studies of sodium chloride'-7 , magnesium oxides-l3 and lithium fluoride. 14-22 Fracture studies on alkali halide and metal oxide single crystals have been limited despite the fact that these materials have a number of advantages for fracture studies. Because they are transparent, the cracks which form can be viewed in three dimensions instead of in two dimensions as in metals. Also, they exhibit stress birefringence under polarized illumination, which enables the internal stress pattern and, therefore, the distribution of dislocations to be examined in the vicinity of the fracture. Early workers1-4 have shown that ionic crystals with a cubic structure fracture in tension along the (100) plane normal to the applied stress. These fractures were brittle at room temperature and propagated very rapidly across the cross section of the crystal. More recently, Stokes, Johnston, and Lil0 have studied crack formation in compressed magnesium-oxide single crystals. They found that the cracks, which were observed after about 3 pct strain, formed in the region of a kink band and lay on conjugate (110) slip planes instead of the usual(100) cleavage plane. Two different types of cracks were noted: stroh23 and secondary. The Stroh cracks did not exist merely on the surface but extended through the specimen in the form of tiny slits. A secondary

Jan 1, 1962

By Thomas E. Howard

Scientific research in mining has a comparatively short history. So long as it was possible to maintain adequate mineral supplies by long-established methods, there was little need for the scientific approach. That the end of this comfortable situation is at hand is evinced by the variety and rapidly growing amount of mining research in progress all over the world. The pattern of development of mining research in other countries shows that it started only after a problem became critical. Therefore, the work generally has been short range and usually concentrated on a specific problem. An example is the preoccupation in western Europe with the problem of strata control.

Jan 1, 1962

By J. A. Morgan, R. E. Lund, D. E. Warnes

The design, operation, and performance of an integrated pilot plant for recovering zinc and copper from a complex sulfide ore are described. Metallurqical processing comprised selective sulfate roasting in a fluid bed, leaching in a weak sulfuric acid solution, recovering copper by cementation with scrap iron, air oxidation to remove soluble iron, more-or-less conventional Purification for removal of impurities deleterious to zinc electrolysis, recovering zinc by electrolyzing solutions, and recycling spent electrolyte to the sulfating roaster. The effects of several feed preparation and roasting variables on the sulfation response of zinc, copper, and iron are set forth, together with the electrolyzing characteristics of the zinc solutions. SEVERAL years ago, St. Joseph Lead Co. undertook a research program to develop procedures for winning values from a complex ore. The deposit was a massive sulfide ore body containing upwards of 65 pct pyrite. Gangue, composed principally of quartz, calcite, dolomite, and alumina, comprised only 10 to 20 pct of the mineralized zones. Zinc, lead, and copper values were variable, but averaged about 6.7 pct Zn, 2.6 pct Pb, and 0.4 pct Cu. Early in the exploratory test work, it was established that the intimate physical association of the minerals in the ore made beneficiation by conventional flotation procedures difficult. Accordingly, in addition to a comprehensive program to investigate physical methods of ore beneficiation, a research program was established to develop a direct metallurgical method for processing the ore. After surveying a number of potential methods for recovery of both metal and sulfur values, effort was concentrated on the development of a sulfate roasting process. It is the pilot-plant development of the sulfate roasting-solution purification—electrolyzing procedures which forms the subject of the present paper. PREPILOT PLANT INVESTIGATIONS From a thermodynamic viewpoint, it is feasible to sulfate selectively a host of metals, including Zn, Cu, Pb, Cd, Ni, and Co, in an iron sulfide ore without sulfating iron. Of course, a number of conditions such as roasting temperature and gas composition must be controlled. In addition, as first disclosed by Hybinette,' an alkali metal salt is frequently beneficial in promoting the sulfation reactions. The application of fluid bed roasting to the sulfate roasting of nonferrous metals was pioneered by Stephens of Battelle Memorial Institute.' Subsequently, Falconbridge Nickel Mines, Ltd. developed an unique process for selectively sulfating and recovering nickel, copper, and cobalt from their nickeliferous pyrrhotite, which recently has been described in an excellent paper by Thornhill.3 One of the unique features of the Falconbridge process is that the feed is introduced into the fluidized roasting furnace in a manner such that the feed slurry is broken up into droplets and the droplets lose their moisture before contacting the surface of the fluidized bed. The dried droplets do not tend to cake or fuse, but rather remain as discrete agglomerates of concentrate particles and roast without significant degradation. St. Joseph, aware that Battelle Memorial Institute had participated in the development of the Falconbridge process, obtained permission from Falcon-

Jan 1, 1962

By John W. Cahn, John E. Hilliard

Single crystals of copper and silicon-iron were cold rolled in orientations chosen to produce individually the major components of the poly crystalline deformation texture. The orientation dependence of the recrystallization kinetics was studied relative to the primary recrystallization textures of these specimens. It is not possible to rationalize the poly crystalline re crystallized textures on this basis. The results suggest an important role of the interaction of adjacent crystals during the deformation of aggregates. BRICK and Williamson1 first noted evidence that the recrystallization temperature was different for straight-rolled and cross-rolled copper given comparable reductions. Michalak and Hibbard2 investigated quantitatively the effect of rolling procedure on the kinetics of recrystallization of cold-rolled copper and found that material cold-rolled the same amount by straight-pass, cross-pass, and compression-pass techniques developed different deformation and recrystallization textures, different 1-hr recrystallization temperatures, and different recrystallization kinetics. However, the temperature dependence of the rate of recrystallization was essentially the same for all techniques. Similar results were obtained on iron. Dunn and Koh3 in studying the recrystallization textures of cold-rolled silicon-iron single crystals reported large differences in the annealing temperatures and times required to recrystallize specimens of different orientations cold-rolled the same amount. Liu4 and Liu and Hibbard5 utilized the concept of different recrystallization temperatures for different orientations of cold-rolled crystals to rationalize the difference in recrystallization textures found in various face-centered-cubic metals. Their explanation predicted a significant difference in the recrystallization kinetics of deformed (110) [112] crystals as compared to (358) [352] crystals, and, in fact, Liu4 reported evidence that this difference existed at least qualitatively. Verbraak6 who rolled and recrystallized a series of copper single crystals found that the double (112) [111] rolled orientation is related to recrystallized cube texture formation. The effect of rolling intensity on the relative amount of cube component suggests an important role of recrystallization kinetics. Walter and Hibbard7 while trying to relate the behavior of rolled and recrystallized single crystals of silicon-iron to the behavior of polycrystal-line silicon-iron again noted that differences in recrystallization kinetics were necessary to rationalize their results. The purpose of the present investigation was to obtain quantitative kinetic data on the recrystallization of single crystals of both copper and silicon-iron rolled to initial isolated individual orientations corresponding to those found in the polycrystalline deformation textures. These data might indicate the importance of the deformation orientation, i.e. the range of available nuclei, the deformed matrix orientation into which these nuclei grow, and the orientation dependence of their growth rate during primary recrystallization on this texture. I. COPPER Experimental Procedure—A single crystal of 99.98 pet purity copper, grown by the Bridgman technique, was purchased in the form of a bar 1 1/2

Jan 1, 1962

By Dale A. Vaughan, Oliver M. Stewart, Charles M. Schwartz

Solid-solubility limits at 1500°, l000q and 500°C for carbon, nitrogen, and oxygen in high-purity tantalum were determined by X-ray lattice-parameter methods. For carbon, the solubility was found to be 0.17 at. pct at 1500°C, and less than 0.07 at. pct at 1000°C. A nitrogen solubility of 3.70 at. pct at 1500° C decreases linearly with temperature to 2.75 at. pct at 1000°C, and 1.8 at. pct at 500°C. In the case of oxygen, the solubility was found to be 3.65 at. pct at 1500°C, 2.95 at. pct at 1000°C, and 2.5 at. pct at 500°C. The phases Ta2C, the low-temperature modification of Ta205, and Ta,N of unknown composition but which has a superlattice structure based upon the original bcc tantalum lattice have been identified as the initial precipitates in the respective systems. Metallographic methods were employed to verify the X-ray analyses. The etching behavior of Ta is discussed in terms of lattice i?rzperfections and precipitate phases. The excellent fabricability, high melting point, and nuclear properties of tantalum are responsible for interest in this refractory metal. Data on the solid solubility of the interstitial elements (oxygen, nitrogen, and carbon) in tantalum and on the precipitate phases are somewhat limited. The significant contributions are discussed below. Because the purity of electron-beam melted tantalum (only recently available) is considerably higher than that used in previous studies, the present investigation was initiated. Gebhardt et all-3 have investigated the tantalum-oxygen and tantalum-nitrogen systems with particular reference to the changes in physical properties and to the rates of reaction between these gases and the metal. The solubility of oxygen in tantalum was reported2 to be 3.7 at. pet at 1500°, 2.3 at. pet at 100O°C, and 1.4 at. pct at 750°C. Schonberg4 reported that several oxide phases (Ta40, Ta,O, TaO and Ta,05) exist while X-ray studies by Gebhardtl showed only two oxides, Ta,05 and an unidentified phase which was associated with a platelet-type precipitate. La-gergren and Magneli,' however, questioned the existence of compounds other than the two allotropic modifications of Ta,05 for the tantalum-oxygen system. In the case of nitrogen, the solubility was estab- lished by Gebhardt3 to be of the order of 7 at. pct at 1800°c. The solubility was reported to decrease rapidly with temperature, and, although no limits were established, a precipitate phase was observed by Gebhardt except when the high-nitrogen specimens were cooled very rapidly from the reaction temperature of 1800c. He reported the initial precipitate phase to be a tetragonal distortion of the bcc tantalum lattice while Schonberg6 reported the phase lowest in nitrogen Jo be a cubic super-lattice with a cell size of 10.11 A. Two other nitride phases, Ta,N and TaN, were reported; these appear to be isomor-phous with the carbides of tantalum. The tantalum-carbon system was investigated by Ellinger7 and by Lesser and Braurer. Two compounds, Ta,C and TaC, were reported to exist, each with a range of composition. The solubility of carbon in tantalum was found to be practically nil at all temperatures. Thus, of the interstitial elements which are present in small amounts in high-purity tantalum, carbon might be expected to form precipitates. The present investigation was initiated to obtain additional data on the solid-solubility limits of these interstitials at 1500°, 1000°, and 500' with particular emphasis on the distribution and the identification of the precipitate phases. EXPERIMENTAL WORK AND RESULTS In the present investigations of the solid solubility and of the precipitate phases in the systems tantalum-nitrogen, -oxygen, and -carbon, high-purity tantalum was reacted with high-purity gases, homogenized at 1800°c, and annealed at and quenched from 1500°, 1000,

Jan 1, 1962

By S. R. Maloof, W. R. Mitchell, J. A. Mullendore

Preliminary experimental evidence is presented to show that the metallic impurities aluminum, iron, and silicon, and beryllium oxide as found in commercially pure hot-pressed beryllium powder can be reduced to lower Concentrations by Zone -Purification techniques. The reduction in the concentration of aluminum to extremely low levels (10 PPm) is noteworthy, since earlier work demonstrated that aluminum is a major factor contributing to the hot-tearing of beryllium during fusion welding. On the basis of present findings, a method is suggested for producing beryllium metal of improved weldability. EXPERIMENTAL research now being conducted on the purification of beryllium indicates that several of the metallic impurities and beryllium oxide can be reduced to lower concentrations by employing standard horizontal zone-refining techniques. For the preliminary work, commercially-pure hot-pressed beryllium having a purity of 97.84 pct was used. The chemical composition is given in Table I. The hot-pressed beryllium was machined into bars 5/8 by 5/8 by 4 to 6 in. in length. Beryllium-oxide boats which had been conditioned by prior heating in a vacuum of 10"5 mm of Hg at 1100°C for 3 hr were used to hold the beryllium while it was zone melted. The boat with its charge, along with a smaller beryllium-oxide boat containing scrap beryllium to be used for gettering purposes, was loaded into a quartz tube and evacuated to 10-6 mm of Hg. Alter alternately evacuating and flushing three times with purified argon, the furnace tube was backfilled to a pressure of 1/6 atm of A and sealed off by means of a vacuum-tight stopcock. It was then removed from the pumping equipment and mounted on the traveling carriage of the zone-refining apparatus. Heating was accomplished with a 10 kw 450 kc induc- tion heating unit using an induction coil consisting of two turns of 3/16-in. diam copper tubing. Before starting to zone melt, the atmosphere in the furnace tube was gettered by heating the scrap beryllium in the smaller boat to above its melting point and holding at temperature for several minutes. The carriage was then shifted so as to locate one end of the beryllium ingot in the large boat within the induction coil. A molten zone approximately 3/4 to 1 in. was established by loading directly into the ingot. The molten zone was moved very slowly along the length of the ingot. Before each pass was made the procedure for evacuating, flushing, and backfilling, and so forth was repeatedI' Speeds of 1 1/2 and 3 in- per hr were used with up to twelve zone passes. The appearance of a typical zone-refined ingot is shown in Fig. 1. After zone refining, the grains in the ingot appear to be elongated in the direction of zone travel, whilst before, they are essentially equi-axed. A microexamination revealed the presence of a network in the beryllium grains as seen in Fig. 2. Laue spots in back reflection pictures taken of the sample were not sharp, indicating the presence of subgrains in the structure. As can be seen, however, many of the network boundaries cross beryllium grain boundaries. It has been shown by Martin and Moore1 that beryllium solidifies as a bcc structure which then transforms to the hexagonal structure at about 1250oC.It is believed that the observed network is merely the outline of the bcc structure which formed from the melt and are not subgrain boundaries. In order to eliminate surface contaminants, approximately 1/16 of an inch of material was removed from the outer skin of each ingot after zone refining.

Jan 1, 1962

By C. G. Dunn, J. L. Walter

COULOMB' and Coulomb and Lacombe2,3 have recently discussed secondary recrystallization in soft iron (99.5 pct Fe). They found that the appearance of this phenomenon was dependent on both the presence of impurities and the thickness of sheet specimens. They concluded that impurities such as carbon, sulfur, and oxygen in the soft iron stabilized the matrix structure and allowed growth of a few grains of specific orientations. They also found that secondary recrystallization ceased when the final thickness was small and attributed this complete inhibition of growth in thin sheet to the restraining action of thermal grooves. When purer iron (99.99 pct Fe) was used, normal grain growth but not secondary recrystallization was obtained. On the other hand it is known that the necessary stabilization of the matrix structure for secondary recrystallization in high-purity silicon iron probably does not depend on impurities but more likely results from the specimen thickness effect of Beck et al.,4 according to evidence and ideas advanced by Walter and Dunn,5,6 and Detert.7 Furthermore, Mullins8 has indicated that if a gas-metal surface energy difference exists across a grain boundary equal to or greater than about 3 pct of the grain boundary energy, then such a grain boundary should not become stuck. Similarly, Walter and Dunn have estimated that any increase in restraining force due to increased thermal grooving with decrease in

Jan 1, 1962

By O. Herstad, J. M. Toguri, K. Grjotheim

DURING the last three years, investigations on the aluminum reduction of magnesium-bearing compounds have been initiated at the Institute of Inorganic Chemistry, The Technical University of Norway. The results of these investigations are reported in this paper. Very little information exists in the literature on the reaction between magnesium compounds and metallic aluminum. The available information itself is conflicting, and, to clarify the existing discrepancy, the reactions between aluminum and magnesium oxide (MgO), caJcined dolomite (CaO . MgO) and olivine (Mg2SiO.) were studied. The logical approach for the study of these reactions between condensed states with the formation of a gaseous phase is, ( 1) the measurement of the equilibrium vapour pressure of the gas, in this case magnesium, associated with the respective reactions and, (2) the identification of the end products of the reaction in order to establish the re-action scheme.

Jan 1, 1962

By Ralph C. Flow

In Cleveland County, North Carolina, one and one-half miles south of Kings Mountain, Foote Mineral Company operates an open pit for the production of spodumene, feldspar, mica, and commercial stone. Spodumene concentrate is sent to Footers Sunbright, Virginia plant and to other customers. Exton, Pennsylvania and New Johnsonville, Tennessee plants produce lithium compounds sold to the oil industry for multipurpose lithium-base greases, to the metal industry as welding flux, to the air conditioning market, and to the glass industry. Ceramic grade spodumene, feldspar, and mica concentrates go to other processing companies from the Kings Mountain plant. Waste amphibolite is delivered to a neighboring quarry operation.

Jan 1, 1962

By C. Altstetter

THE work herein reported is restricted to the carbides which occur in quenched and tempered AISI 43XX steels with carbon contents up to 0.40 pct and silicon additions of up to 3 pct. In view of the instability and extremely small size of the carbides formed at low tempering temperatures, the technique for successfully preparing specimens for X-ray diffraction will be outlined. The alloys listed in Table I were obtained through the courtesy of the United States Steel Corp. in the form of 1/2-in. rounds forged from 100 lb. induction furnace heats (except for 4337 which was a commercial heat). The stock was normalized and then swaged and drawn to 15 mil wire with anneals at 1200F between passes. The wire was austenitized for 45 min in evacuated vycor capsules and quenched into iced brine with simultaneous smashing of the capsule. Tempering was done in air with a water quench after tempering. The carbides were extracted in a simple cell using a solution of 1M KC1 and 0.5 pct citric acid with an initial current density of 0.1 amp per sq cm. One end of a short length of wire was immersed in the solution, and the current at constant voltage was noted as a function of time. After about an hour the current dropped sharply because of the decrease in specimen cross-section. At this point it was found that the dissolution could be stopped and that the very fine wire which then resulted was just large enough to permit handling of the extracted precipitate still clinging to it, yet so small that it diffracted and absorbed only a negligible amount of the X-radiation. This rod of residue with a convenient handle of undissolved wire was rinsed in distilled water. alcohol, and acetone. Then it was dipped in a thin solution of cellulose-acetate cement and dried in vacuum. The resulting specimen was straight, uniform in density, easily handled, but most important, was completely sealed and never exposed to air. Furthermore, the residue had never been subjected to strong acids or rough handling such as in the extraction-replica technique or in the complete extraction to a powdered residue. It was found that improperly coated specimens were pyrophoric, turning to oxide with a dull red glow as they were exposed to air and yielding patterns of Fe2O3 and Fe3O4. The steels containing 3 pct Si were especially difficult to prepare for this reason. The specimens were put in a 57 mm Straumanis camera with double pinholes or slits and irradiated with filtered-chromium radiation. Readable patterns were obtained in less than an hour. A preliminary finding of some note was that for both tempered and as-quenched specimens of steels 4337 and 4337 (1.5 Si). M23C6 patterns were found along with the patterns of other constituents of the residues. This result was somewhat surprising in that previous investigators had reported that this carbide did not appear in a 0.38 pct C, 0.48 pct Mo steel1 or in chromium steels of less than about 10 pct Cr.2 Although the total amount of carbide-forming alloying elements is less than 2 pct, due to their mutual interaction and the action of the plastic deformation in promoting equilibrium, this carbide was able to form even in the steel containing 1.5 pct Si. M23C6 was not detected in the 4337 (3.0 Si) steel and the lower-carbon steels were not investigated in this condition. It is very likely then that the steels studied herein underwent a fourth stage of tempering during the anneals at 1200°F. This result has significance in that even a small amount of undissolved M23C6 in a low-carbon, low-alloy steel would exert a large effect on its hardenability. Its presence would also influence the mechanical properties by decreasing the carbon content of the matrix. Annealing in vacuum for 1 to 4 hr in the austenite field removed all traces of MZ3C+ The results on carbide precipitation during tempering, summarized in Table I, are in agreement with those of Klingler et al.3 for the higher carbon steels. For the AISI 4337 steels it is noteworthy that in the steels with added silicon the E carbide persists to longer times and higher temperatures and that silicon delays the formation of cementite. The results for the lowzr-carbon steels parallel those of the higher-carbon grade. The appearance of E carbide in the AISI 4315 is significant. There is considerable disagreem-nt in the literature as to whether this carbide forms in the tempering of steels containing less than about 0.2 pct C. Following the detection of E carbide in a 0.18 pct C plain-carbon steel,4 its occurrence in a steel containing chromium and molybdenum should be expected. The fact that the low-carbon steels have the same carbide-precipitation sequence as the high-carbon steels has bearing on the larger problem of the exact tempering reactions in all steels. Following the suggestion of Roberts et al.,' the first stage has been generally assumed to result in a metastable equilibrium of c carbide and martensite of about 0.25 pct C. From this it was concluded that a steel having less than 0.25 pct C should then be under-saturated with respect to c carbide and should not precipitate this carbide upon tempering. In view of the experimental findings of c carbide in steels hav-

Jan 1, 1962

Differentiation of a basaltic (?) magma occurred in an active volcanic area during the late Miocene and Pliocene, and a change in the general mode of extrusion from fissure flow for the basalt to explosion for the andesite reflects an accompanying increasing magmatic viscosity. A caldera formed after the flow phase was completed and was filled with coarse agglomerate, much of which has a fused appearance. After an erosion interval its shape was modified and it became gradually deeper as repeated explosions from growing andesitic volcanoes caused large quantities of pyroclastic material to be deposited. At the close of this phase the floor abruptly collapsed when a, large block of the underlying crust was engulfed. The incompetent pyroclastics filling the caldera steepened in dip and the ensuing fractures were filled by the rising magma as dykes and sills and a chonolith formed below the caldera at a shallow depth. The ensuing activity reveals a further stage in differentiation and biotite is an important new ferromagnesian to be observed in the new rocks.Fracturing of the surrounding basalts was most intense in the rocks forming the periphery of the caldera where steeply and flatly dipping faults resulted from increasing horizontal pressure directed towards the caldera.Further differentiation resulted in the increased crystallization of orthoclase felspar, as evidenced by the numerous intrusives of trachy andesitic composition. Magmatic freezing caused mineralizers to accumulate at the top of the chonolith. These eventually escaped and auriferous pyrites, tellurides, quartz, and calcite were deposited in the surrounding rocks.The flatly dipping fractures are the most important and can be expected at various depths in a zone about 4,000 ft wide surrounding the caldera. Latest movement along these was controlled by magmatic consolidation rather than the shape of the caldera. Some flat faults were able to remain open during mineralization and acted as a feeder for the shallower fractures, thus limiting the depths to which the steeper dipping fractures were mineralized with the possible exception of one particular Nw.-striking lode (the Crown-Crescent).INTRODUCTIONThe gold deposits of the Tavua district were discovered in 1932 and from 1935 to June, 1961, 1,985,041 fine ounces of gold were produced from 4,202,504 tons of ore. Of the original three producers, only the Emperor remains active in the...

Jan 1, 1962

By H. Margolin, E. Ence

In order to understand the effect of zirconium on properties of Ti-Cu-A1 alloys, Ti-Zr alloys were examined for the presence of ordering or compounds at the following compositions in weight percent: 24.1 pct Zr (lZr:GTi), 32.2 pct Zr (lZr:4Ti), 38.8 pct Zr (lZr:3Ti), 49.0 pct Zr(1Zr:ZTi). Alloys were prepared as 15-g buttons by non- consumable arc melting under argon atmosphere from Bureau of Mines titanium (Bhn 63) and Reactor Grade zirconium (Bhn 150). Weight losses during melting did not exceed 1 pct of the initial button weight. Prior to heat treatment, buttons were hot-rolled at 600" to 700°C to rods of about 6 mm diam. Contamination after hot-rolling was found to extend to a depth of less than 0.5 mm. Specimens for heat treatment were wrapped in molybdenum sheet, annealed in argon-filled quartz capsules, and quenched by breaking the capsules under iced brine. Annealing times were as follows: 700°C — 7 days; 600°C— 14 days; 575°C-1 and 2 months; 525°C-2 months; 500°C-2 months. Prior to heat treatment, all Ti-Zr alloys were vacuum annealed at 900°C to remove hydrogen. The reanneal of 575°C specimens for an additional month produced no observable microstructure changes. The results obtained by microstructure and X-ray diffraction are shown in Fig. 1, together with data of Hayes et al.' No other phases than a or P were found. Small amounts of retained P were detected by X-ray in the 49 pct Zr alloy. The data of the present investigation suggests that ß and a transus boundaries are at considerably lower temperatures than those of Hayes et al. The work of Hayes et al. is based on sponge titanium and Bureau of Mines zirconium, both of which contained 0.15 pct 0. Since melting was performed in

Jan 1, 1962