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By T. L. Fritzlen

Extrusion of aluminum alloys in this country is performed mainly by direct extrusion, therefore this paper is confined only to factors affecting the rate of extrusion by this method. Many factors affect the rate of extrusion of aluminum alloys. It is the purpose of this paper to present a discussion on the factors that are subject to technical control. Most of them are closely related, so that a clear-cut distinction between them is rather difficult. However, an attempt will be made to evaluate the effect of each factor separately, as far as possible. The most important factors only will be considered, and these will be discussed in detail under three general headings: (I) characteristics of the equipment, (2) size and structure of the ingot, and (3) temperature of ingot, cylinder, and other parts. It is a well established fact1 that the pressure and the speed of extrusion are related and are exponential functions of one another. Therefore, whenever a certain condition tends, for instance, to increase the pressure required for extrusion, it will reduce the extrusion speed if the pressure is maintained constant. For this reason, in this paper the effect of various conditions is expressed either in regard to their effect on the pressure required or the extrusion speed. Another established fact is the relation- ship between the temperature of the material being extruded and the pressure required to extrude. According to Schi-shokin,= this relationship is of the exponential type, and as the temperature is increased the pressure required is decreased. It would seem from the preceding that the greatest rates of extrusion can be obtained by the use of higher temperatures. However, as is well known, other factors intervene to limit the rate of extrusion of aluminum alloys when increasing the temperature. These factors will be discussed in detail later. Characteristics of the Equipment The capacity of the press determines * the maximum unitary pressure that can be applied for any given cylinder diameter. Pressures used for extrusion of aluminum alloys range from approximately 50,000 lb. per sq. in. to 150,000 lb. per sq. in., dependent upon the alloy and the size of the shape extruded. Higher pressures could be used to advantage, but existing steels limit pressures employed in the production of extrusions. Numerous mechanical characteristics of the extrusion press affect extrusion rate. The most important characteristics of the press itself are: (I) sensitivity of the main pressure valve and accuracy of pressure gauges, (2) accuracy of equipment to heat the cylinder uniformly and to control cylinder temperature, and (3) accuracy of means of measuring the speed of extrusion. The variables subject to control during the extrusion operation are pressure, temperature, and speed, and it is evident that the preceding characteristics

Jan 1, 1946

By Henry Carlisle

W. W. Mein: One of the most amusing things in Nevada City – I was born and was going to school there - was that my mother made overcoats for us, and because they were different from other boys’ overcoats, we’d hide them under a bridge and pick them up on the way home. I left Nevada City with my parents when I was about eleven years old, and moved to Oakland. This was caused by the closing down of the hydraulic mines and my father being send to the El Cayo mine in Venezuela, which was then one of the richest gold mines in the world. Hamilton Smith operated the hydraulic mines in California, and when they were closed down by the Sawyer decision, he was persuaded by the Rothschilds to go to London. There, together, they formed the London Exploration Co.

Jan 1, 1964

By B. G. Reisdorf

This paper describes the microstructural changes that occur when quenched ultrahigh-strength steels containing OA pet C and various amounts of nickel, silicon, and cobalt are tempered. The changes that occur in hardness, yield strength, and martensite diffraction-peak widths when these steels are tempered are related to the precipitation of the carbide phases. An unea$ectedly high silicon content (about 30 pct) was found in the E -carbide phase in a steel containing only 1.5 pct Si. TEMPERED martensitic steels have such wide-spread utility that they have been the subject of numerous investigations, and a sizable amount of literature has developed on this subject.M This investigation, which is a part of a larger program to correlate microstructure with mechanical properties at a variety of strength levels, is limited to the microstructural changes that occur when a quenched 0.40 pct carbon steel (USS Airsteel X-200 steel) is tempered, and to the effects of the alloying elements—nickel, cobalt, and silicon—on these microstructures. Used in this investigation were electron microscopy, electron-diffraction identification of the carbide phases, electron-probe micro-analysis of the carbides, X-ray determinations of retained austenite, and measurements of martensite X-ray diffract ion-peak widths. MATERIALS AND METHODS The chemical analyses of the eight heats examined eats No. 30 through 37) are shown in Table L Heat No. 30 has the chemical com~osition of Airsteel X-200, and the remaining seven heats contain various amounts of nickel, chromium, cobalt, and silicon. The heats were air-melted in an induction furnace and cast into 8 by 8 in. ingots that were subsequently heated to 2300 and rolled to 1-in.-thick plate. Oversize 0.505-in.-diam tensile specimens were rough-machined from the plates and austenitized in air at 1700° F for half an hour and oil-quenched. The specimens were then tempered in air at temperatures of 400° to 1000 for tempering times of 1, 4, and 16 hr, and finish-machined to 0.505-in.-diam tensile specimens. Electron micrographs were prepared from Formvar replicas of the midthickness of tensile-specimen shanks that had been electrolytically polished and etched in nital. Electron-diffraction patterns were obtained from carbon-extraction replicas. The replicas were prepared by etching the sample surface in the same manner as for microscopy, evaporating carbon on the etched surface, and re-etching the sample to free the carbon film and the precipitate particles. Electron-probe microanalysis was performed on some of the extraction replicas. To obtain adequate fluorescent X-ray intensities, several thicknesses of replica were exposed to the electron beam so that the results represent an average composition of the extracted particles rather than an analysis of single precipitate particles. The retained austenite contents of the specimens were determined by an empirical X-ray diffraction

Jan 1, 1963

By W. T. Turrall, D. Porter

THE crystal laboratory, Dept. of Physics, Massachusetts Institute of Technology, was confronted with the problem of obtaining a supply of optical grade calcium fluoride (CaF2) for use in growing synthetic CaFe2 crystals. A search of the known fluorspar deposits did not indicate that any quantity of optical spar could be obtained. Even the best material had to be sorted by hand to remove impurities. The process for growing CaF2 crystals developed by Professor D. C. Stockbarger of the Dept. of Physics, M.I.T., necessitates very pure feed materials. Exclusion of impurities is required, even in amounts detectable only spectrographically. The impurities occurred as minute inclusions of SiO2, BaSO4, CaCO3, FeS2, water or air. Crystals up to 4 in. in diam and weighing several pounds are made by the Harshaw Chemical Co. in Cleveland. Since the time required to grow a 4-in. crystal is about one week, and since the cost of manufacture is high, removal of impurities by any concentration method appeared practical. The mineral engineering section of the Dept. of Metallurgy undertook to investigate the possibility of concentrating clear optical fluorspar, -4 mesh +10 mesh, from a feed containing over 99 pct CaF2. Various innovations of the known methods of concentration were considered, but in each case the minute amount of impurities associated with the crystal produced such extremely small differences

Jan 1, 1952

By W. O. Philbrook, K. Natesan

The oxidation kinetics of spherical pellets of zinc sulfide made from Santander concentrates were studied using a thermogravimetric technique. The experiments covered a temperature range-. of 740" to 102O°C, 0-N mixtures varying from 20 to LOO pct O2, and pellet diameters between 0.4 and 1.6 cm. Mathematical models were formulated to Predict the reaction rate on the assumption that a single transport or interface reaction step was rate -controlling. Analysis of the data indicated that the process of oxidation was predominantly controlled by transport through the zinc oxide reaction-Product layer. ROASTING processes, which are reactions between solids and gases, are very important because they are employed in the production of a number of basic metals. These processes are highly complicated, and one needs to consider the transport phenomena of heat and mass between the solids and gases in addition to the kinetics of various chemical reactions involved. Because of such complications there is a lack of knowledge concerning the rate-limiting factors, which may strongly depend on temperature, particle size, gas composition, and solid structure. The oxidation of zinc sulfide, which is of commercial importance in zinc production, falls into this class of reactions. The major goal of this work was to elucidate the roles played by different process variables, such as reaction temperature, gas composition, pellet size, and pellet porosity, on the kinetics of oxidation of single pellets of zinc sulfide. Roasting of zinc sulfide single particles has been a subject of both experimental and theoretical investigations.&apos;-&apos; The reaction is exothermic and may be considered to be irreversible. Such a reaction has been found to proceed in a topochemical manner. In other words, as the reaction proceeds, a progressively thicker outer shell of zinc oxide is formed, while the inner core of unreacted sulfide decreases. It has been found experimentally, both in the present work and in the previous investigations,1-9 that the particle retains its original dimensions and the process requires transport of gaseous oxygen across the porous product layer for continued reaction. The reaction may be represented by ZnS(s) + 3/2 O2(g) = ZnO(s) + SO2(g) [1] The solid product considered here is only zinc oxide, since the diffraction patterns of zinc sulfide pellets oxidized partially at &apos;798" and 960°C showed K. NATESAN, Junior Member AIME, formerly St. Joseph Lead Fellow, Department of Metallurgy and Materials Science, Carnegie-Mellon University, Pittsburgh, Pa., is now at Argonne National Laboratory, Argonne, Ill. W. 0. PHILBROOK, Member AIME, is Professor of Metallurgy and Materials Science, Carnegie-Mellon University. This paper is based on a them submitted by K. NATESAN in partial fulfillment of the requirements for the Ph.D. degree in Metallurgy and Materials Science at Carnegie-Mellon University. Manuscript submitted December 2, 1968. EMD lines corresponding to original zinc sulfide and the newly formed zinc oxide. OXIDATION MODEL The generalized model for gaseous oxidation of zinc sulfide is illustrated in Fig. 1. This depicts a partially oxidized sphere of zinc sulfide in a gas stream surrounded by a laminar film of gas. The spherical sample of zinc sulfide of unchanging external radius r0 is suspended in a flowing gas stream of total pressure PT and composition specified by the partial pressures of the individual components. Partial pressures of the gaseous species in the bulk gas phase, at the exterior surface of the pellet, at the ZnS/ZnO interface, and at equilibrium for Reaction [I] are identified by the superscripts b, o, i, and eq, respectively. The overall reaction involves the following ~te~s:&apos;~&apos;~&apos; Step 1. Transfer of reactant gas (oxygen) from the bulk gas stream across the gas boundary layer to the exterior surface of the pellet and the reverse transfer of the product gas (sulfur dioxide). Step 2. Diffusion and bulk flow of oxygen from the pellet surface through the product shell (ZnO) onto the ZnS/ZnO interface and the reverse transfer of sulfur dioxide. Step 3. Chemical reaction at the interface, which results in consumption of oxygen gas and generation of sulfur dioxide gas and heat; at the same time the _________ PARTICLE SURFACE / x^^^^n^X / MOVING INTERFACE core-----/ sJSNxy " /T^T^02 \ V\V$\ ^NWX/ "*/— GAS BOUNDARY x. \\ZnO SHELLV/ / \^ . / &apos; ^ BULK GAS --------N_______ _____,------p£ w \ P« / (f> \ / a \ <i) / <----------------- _(o) ^^--------------(b) °- pso, pso2 ro ri 0 ri ro RADIAL POSITION Fig. 1—Generalized model for oxidation of a sphere of zinc sulfide.

Jan 1, 1970

By H. O. Hofman

The object of refining copper in the reverberatory furnace is to obtain a metal which will have the highest attainable degree of malleability, ductility and electric conductivity, and present at the same time a level surface when it solidifies in the mold after casting. These desirable physical properties are governed by the character of the impurities and the forms in which they are present, by the amount of cuprous oxide retained by the copper, by the quantity of gas held in solid solution, by the casting-temperature, and by the thickness of the casting. The effects of impurities, of cuprous oxide and of gases upon the mechanical properties of copper have been studied by Hampe1 in his classical paper " Colitributions to the Metallurgy of Copper." The most recent research into the effect of metals upon the electrical conductivity of copper is that of Addicks. 2 The influence of cuprous oxide upon the electrical conductivity has been investigated by Walker3 and Addick. 4 The absorption of gases has received attention by Hampe: Stah16 and Heyn 7 The effects of casting-temperature have been noted by Stahl.8

Jan 1, 1908

FOR this Famous Mining Enterprise issue MINING ENGINEERING selected the company that started the zinc in dustry in the United States. The New Jersey Zinc Co. has been a supplier of zinc products to the nation&apos;s industries for more than 104 years. Its Horse Head trade mark is famous throughout the world.

Jan 12, 1953

By L. E. Young

THE purpose of this paper is to start a discussion on: (1) methods of supporting the immediate roof, particularly of local areas of poor roof, during the mechanical loading of coal; (2) methods of increasing the rapidity of the movement of the mining faces so that, without the use of cribs, jacks, pack walls, and filling, there will be no danger to men, equipment,, and working places from the subsidence of the overlying strata. In the Pittsburgh district the application of mechanical loading devices in mines working in the Pittsburgh seam, has been retarded by the difficulties of holding and handling the draw slate. Normally the thickness of this slate averages about 8 in. but the hardness varies, and a cut of coal cannot always be loaded without placing posts or crossbars to support the slate. Locally, the slate may be thicker and special methods of support may be required. If crossbars are placed to hold the slate when the coal averages 5 ft. in thickness, the standard methods of transporting the coal cannot be followed, and the use of conveyors may be desirable. Very little information is available on the effect of increasing the rate of movement of advancing or retreating break lines or longwall faces. A few British publications have presented some data but all such data relate to longwall faces that have moved not more than 6 ft. a day. The most rapid rate of movement of longwall faces in Germany is 6 ft. per day. In the ordinary hand-loading mine in western Pennsylvania break lines on full retreat will move about 2 ft. per day. If loading machines are used under similar conditions the, rate of retreat may reach 4 ft. per day. In a mine where coal is loaded by hand on conveyors three shifts per day, the rate of retreat has ranged from 11 to 16 ft. per day, with an average of 13 ft. If mobile loading machines could be used to load on con-veyors on break lines, the rate of retreat should be increased substantially.

Jan 1, 1938

By A. B. Young

In the original design of the flue system, the flues from the roasters delivered their gases to a large brick dust chamber which discharged into another flue with stack connection, as shown in Fig. 1. The treater is so situated that the gases are taken by it directly from the chamber and discharged again into the flue. The complete installation comprises two treater units, only one of which has been installed at present. The treater is essentially a flue 1.0 ft. high, 12 ft. wide, and 61 ft. long. (3 by 3.6 by 18.5 m.). Suspended inside, vertically and running lengthwise, are four banks of No. 20 corrugated iron plates; each bank is 10 ft. long, making an effective treater length of 40 ft. The spacing from center to center of the rows of plat,es is 9 1/8 in. (23 cm.) giving six-

Jan 1, 1921

By Sandford S. Cole, John S. Breitenstein

The recovery of over 80 pct of the vanadium values in titaniferous magnetite from Maclntyre Development,Tahawus, N. Y., was accomplished by an oxidizing roast with Na2O3-NaCI addition. Process description is given for leaching of roasted ore and precipitation of V2O5 and Cr2O8 from leach liquor. THE exploration and development of the Mac-Intyre orebody at Tahawus, N. Y., by the National Lead Co. provided a source of vanadium. Analyses of various composite sections of the drill cores of the MacIntyre orebody were made to establish whether or not the vanadium was constant throughout. Ten drill cores were sampled as 50 ft sections, crushed, and a portion magnetically concentrated. The head and concentrate were analyzed for total iron and vanadium. The results on the concentrates indicated that the vanadium is associated with the magnetite and maintains a close ratio to the iron content. The nominal ratio of 1:25:140 of V: TiO2:Fe was found to exist in the concentrates. Typical value for the vanadium in the magnetite both from laboratory concentration and mill production is 0.4 pct. The recovery of vanadium from the magnetite was investigated in 1942 to 1943. The research program encompassed both laboratory and pilot-plant work on sufficient scale to provide adequate data to establish the feasibility of a full scale plant. The recovery of vanadium from various ores has been reported in the literature and has been the subject of many patents. The literature dealing with recovery from titaniferous ore by roasting is quite limited. Roasting with alkaline sodium chloride, sodium chloride or alkaline earth chlorides, and sodium acid sulphate have been claimed in various processes as effective means.1-8 The reduction of the ore, followed by acid leaching, was another method proposed.&apos;-&apos; "he use of various pyrometallurgical processes for recovery of vanadium in the metal or in the slag has also been extensively investigated, but the results had little application to the problem."-" The separation of vanadium values from subsequent leach liquors and vanadium-bearing solution has been the subject of a considerable number of papers and patents. The most practical is by hydrolysis at a pH of 2 to 3 by acidifying a slightly alkaline solution. Data on solubility of V²O5 and V2O4 in water and in dilute sulphuric acid indicated a solubility of 10 g per liter in water.&apos;" Laboratory Results Magnetite Analysis: Adequate stock of magnetite was provided so that the laboratory and pilot-plant operation was on ore representative of the mill production. The ore was analyzed chemically and examined by petrographic methods to ascertain whether the vanadium was present in combined state or as an interstitial component between grain boundaries. No evidence was obtained which would indicate that the vanadium was in a free state as coulsonite.15 The analysis of the ore was as follows: Fe²O³, 47.4 pct; FeO, 29.1; TiO,, 10.1; V, 0.40; and Cr, 0.2. The screen analysis of the ore on the as-received basis was: -20 +30 mesh, 28.8 pct; —30 +40, 18.9; -40 +50, 9.7; -50 +60, 15.1; -60 4-100, 5.9; -100 + 200, 11.2; -200 +325, 3.7; and -325, 7.2. Roasting Conditions: The prior practice indicated that a chloridizing roast with or without an alkaline salt had been effective on other titaniferous magnetites. On this basis roasts with additions of sodium chloride, sodium carbonate and mixtures thereof were investigated varying the roasting temperature between 800" and 1100°C. Since the ore had shown no segregation or concentration of vanadium, the influence of particle size on the freeing of vanadium by the reagents during roasting was determined. The initial work was on silica trays in an electric resistance furnace with occasional rabbling of the charge. Subsequently, the roasting was carried out in a small Herreshoff furnace to establish the influence of products of combustion on the recovery of the vanadium. The laboratory tests showed that this ore required an alkaline chloridizing roast, in conjunction with a reduction in particle size to less than 200 mesh. When roasted in air at 900 °C with 5 pct NaCl and 10 pct Na2CO³, over 80 pct recovery of the vanadium was attained as a water-soluble salt. The presence of alkaline earth elements gave detrimental effects and care had to be exercised to avoid any contamination of the ore or roast product by such materials. The solubilization of vanadium under the various conditions is given in a series of curves in Figs. 1 to

Jan 1, 1952

By J. F. Smith, J. R. Ogren, N. J. Magnani

The uapor pressrcres of magnesium over binary alloys of magnesium with twelve of the yare-earth eletnetzts have been measured by the Knudsen effuion method in the temperature range 675° to 910°K. These vapor-pressure measurments were combined with data concerning the tevtrlitzul magnesium solubility and the vapor pressure of pure magnesinm to evaluale the standuvd free energies of pluase jormation. These free-etzergy values indicate that the CsCl structures of the heacy rave earths tend to be somewhat less stable than those of the light rare earths. This dif-]eying- behaviov covrelates with differences which have been obsevz~ed in other alloy systetns wherein a phuse appeurs, disappeavs, or changes crystal stvucture as the atomic number of the rare-earth com-ponent is changed. This behauior also appears to correlate with the struclurul rariations within the rare-earth elements themselves, and it is speculated that cariations in the spatial extent of the 4f orbitals are responsihle. STUDIES of the phase relationships and crystal structures in the binary systems between rare-earth metals (lanthanons) and magnesium are extensive but far from complete. However, the currently available information1-10 does produce a rather interesting pattern. This is illustrated in Table I. If one excludes europium and ytterbium from consideration because of their generally atypical behavior, it can be seen from the table that the phase relationships in the magnesium-rich regions show a distinctly different pattern for the lighter lanthanons as compared to the heavier lanthanons. For the lighter lanthanons, LnMg2 phases occur from lanthanum to gadolinium with the cubic MgCu2 structure, LnMg3 phases occur from lanthanum to terbium with the BiLi3 structure, and magnesium-rich phases occur from lanthanum to gadolinium with stoi-chiometries between Ln5Mg42 and LnMg12. In contrast, for the heavier lanthanons, those LnMg2 structures which have been examined have the hexagonal MgZn2 structure, LnMg3 phases have not been observed beyond terbium, and the magnesium-rich phases occur with the a manganese structure near a stoichiometry of Ln5MgZ4. The heavy lanthanon-magnesium systems thus appear to be analogous to the Y-Mg system""2 wherein YMg has the CsCl structure, YMg2 has the MgZn2 structure, and the region Y4Mgz5-Y5Mg24 has the a manganese structure, and no other intermediate phases are observed. Similarity in alloying behavior between yttrium and the heavy lanthanons occurs commonly, and on this basis it seems likely that LnMg2 phases will be found with the MgZn2 structure in the binary systems of dysprosium, thulium, and lutetium with magnesium when the appropriate investigations are made. In the case of the magnesium-rich phases of the lighter lanthanons, only the Ce-Mg phase relationships have been investigated thoroughly and in detail, and until similar investigations are made for the other systems there will remain questions as to which magnesium-rich stoichiometries represent equilibrium phases and what systematic variations occur in the sequence from lanthanum to gadolinium. Thus the data in Table I show that only the LnMg phases occur with the same crystallographic structure throughout the sequence from lanthanum to lutetium. It was speculated that the relative stability of these LnMg phases might vary from one lanthanon to the next in such a way as to presage the differences which occur among the more magnesium-rich lanthanon-magnesium phases. On this basis the present investigation of the thermodynamics of phase formation was Gndertaken for the LnMg phases. PROCEDURE AND RESULTS A generalized phase diagram for the lanthanon-rich portion of a lanthanon-magnesium alloy system is shown in Fig. 1 where ß represents a high-temperature bcc

Jan 1, 1968

By E. C. Wright

THIS paper describes some properties of steels in the composition range 0.10 to 0.30 per cent carbon and 1 to 7 per cent chromium. It is well known that some steels of this type develop high tensile strengths upon receiving comparatively simple heat treatments, such as ordinary air cooling from appropriate temperatures, with "or without subsequent tempering treatments. These high strengths are frequently associated with unusual toughness as measured by the Izod or Charpy impact test. The chromium content, in addition to imparting the above properties, enhances the resistance to corrosion and improves the strength and oxida-tion resistance at elevated temperatures. Moreover, these steels have good forging and fabricating properties, as evidenced by the fact that several thousand tons of seamless tubing have been made during the past five years from steels containing 0.10 to 0.25 per cent carbon and 5 per cent chromium.

Jan 1, 1933

THE CHAIRMAN (G. H. CLEVENGER, Stanford University, Cal.).¬I would like to ask Mr. Pyne if he has had any experience inn the use of chromite as refractory under conditions that are highly reducing? I am reminded of an experience I once had with an electric furnace. I imagined that chromite would form a splendid lining, but it soon disappeared; hence it seems probable that, under highly reducing conditions at a high temperature, chromite is a very poor refractory. F. R. PYNE.-In copper smelting the atmosphere is generally neutral, or slightly oxidizing; we do not use highly reducing atmospheres at all, not even in the matting furnace. You can take the chromite brick and treat it as you would an iron ore, obtaining ferro-chrome very readily, from which the copper will separate. We have done this; in fact, at one time we considered installing a small electric furnace for the production of ferro-chrome. FOREST RUTHERFORD, New York, N. Y.-During the time I was general superintendent at the smelter of the Copper Queen Consolidated Mining Co., at Douglas, Ariz., a great many experiments were made on the furnaces and settlers with different kinds of brick, and I agree with Mr. Pyne&apos;s statements about chrome brick. Their power to absorb metals is very great, and as they cannot be smelted at any temperatures obtainable in a copper furnace, to get rid of the bats and extract the metal from them is quite a problem. We finally got down to using chrome brick only for lining the settlers, out of which we often got a life of upwards of 2 years, and for lining the blast-furnace bottoms, for the reason that chrome brick can be heated and wet, or wet after being heated, without going to pieces, whereas under these conditions magnesite brick will break down very rapidly. We also used a layer of chrome brick above and below an 18-in. band of magnesite brick put on the slag line of the reverberatories, in order to separate the magnesite from the silica brick, fearing that they would slag each other and let the wall drop. The idea worked, but became unnecessary on account of a change made in the method of feeding the furnaces. Chronic brick will not stand up under pressure so well as a good Grecian or Austrian magnesite brick, on account of the poorer bonding properties of the materials from which the chrome brick is made.

Jan 4, 1918

By N. J. Olson, G. W. Toop

A series of equations previously derived for calculating ternary thermodynamic properties using binary data has been applied to the problem of predicting ternary phase diagrams and quaternary excess free energy. The methods are considered to be rigorous for regular ternary and quaternary systerns and empirical for nonregular systems. The equations have been used to predict ternary phase boundaries in the Pb-Sn-Zn system at 926°K and the Ag-Pd-Cu system at 1000ºK. Calculated quaternary excess free-energy values are presented for the Pb-Sn-Cd-Bi system at 773°K. A method for predicting the location of ternary phase boundaries would be a useful supplement to experimental measurements in ternary systems. This has been recognized with the considerable work that has been done to find models to predict or extend thermodynamic properties and phase diagrams in binary and ternary systems1-18 for which direct experimental measurements are limited. With the access to highspeed digital computers and mechanical plotting devices, it is currently rather easy to compare mathematical models with experimental data. The regular-solution model is consistent with systems which exhibit negative heats of mixing, positive heats of mixing, and miscibility gaps, and therefore it is applicable to simple phase diagrams. The purpose of this paper is to illustrate the use of regular-solution equations to predict, empirically, phase equilibria in some types of nonregular ternary systems. Corresponding equations for regular quaternary systems are given and used to calculate empirical quaternary excess free-energy data. METHOD FOR PREDICTING THE LOCATION OF TERNARY PHASE BOUNDARIES USING BINARY DATA Meijerin1,6 has used the regular-solution model to calculate common tangent points to ternary free energy of mixing surfaces and hence to determine phase boundaries in ternary systems involving miscibility gaps. He used the following equation to calculate ternary excess free energy of mixing values: stants characteristic of the binary solutions, and Ni is the mole fraction of component i. An alternate expression which gives for regular solutions as a function of binary values of along composition paths with constant N1/N2, N2lN3, and N1/N3 may also be derived:15 ternary r xs 1 ?c-*n.Ti*.U*. This expression for is more useful for the empirical calculation of ternary excess free-energy values for nonregular systems because actual binary AFXS data may be used in the expression rather than attempting to find suitable constants for Eq. [I]. The results of this feature of Eq. [2] are illustrated in Table I where calculated excess free-energy values for the Ni-Mn-Fe system at 1232°K are compared with experimental data of Smith, Paxton, and McCabe.19 Although regular-solution equations have been shown to give calculated thermodynamic quantities which agree quite well with experiment for single-phase nonregular ternary systems,14,15 care should be exercised in the use of the equations to predict thermo-dynamic properties of multiphase ternary systems in which strong compound formation is suspected. This precaution is consistent with the simple regular-solution model which for negative values of ai_j will indicate a tendency toward compound formation but even for very large negative values of ai-jwill not give multiphase binary or ternary systems involving a distinct stable compound. Hence, calculated ternary free-energy data using Eq. [2] might be expected to vary between being rigorous and poor, in the following order, for ternary systems which are: a) regular solutions, b) nonregular single-phase liquids in which random mixing is nearly realized, c) nonregular single-phase solids, d) nonregular multiphase systems exhibiting miscibility gaps, e) nonregular multiphase systems with binary compounds but no ternary compounds, f) nonregular multiphase systems with highly stable binary and ternary compounds. The calculated data will be expected to be least accurate for the last two cases. The general method adopted in this paper involves two-dimensional plots of ternary activity curves. The principle used is that tie lines indicating two-phase equilibria join conjugate phases a and B for example, for which a1(a) = a1(B), a2(a) = a2(B), and a3(a) = a3(B). Tie lines may be determined by plotting the ternary activities of two components along an isoactivity line for the third component and the unique points where the above equalities hold may be found graphically.

Jan 1, 1970

By A. S. Yue, A. E. Vidoz, F. W. Crossman

Tensile specimens were prepared from a single grain of an epitaxially grown Al-CuAl2 eutectic ingot. The eutectic lanzellae were oriented parallel and perpendicular to the tensile axis of the specimens. Since the composite was of the eutectic composition, the aluminum-rich matrix could dissolve up lo 5. 7 wt pct Cu in solid solution and, therefore, was amenable to strengthening by precipitation hardening. The tensile properties of the eutectic single crystals were determined at room temperature as functions of interlamel-lar spacing, platelet orientation, and thermornechanical trealment. The obserced variations in composite stress and modulus with respect to the level of&apos; composite strain are discussed in terms of premature fracture of CuAlz platelets, a distribution function for the strength of the lamellae, and unequal strains due to localized fracture of&apos; platelets. The discontinuous fiber composite model of Kelly and Tyson is modgied to account for a changing distribution of fiber lengths during composite loading. The tensile properties at elevated temperatures were determined for the direc-tionally solidified eutectic oriented with platelets parallel to the tensile axis. The observed properties are attributed to the onset of plasticity of the CuAL2 phase above 150°C. DURING the investigation of whisker- and fiber-reinforced metallic matrix composites in recent years, two major problem areas have developed: 1) The fabrication of the composite involves tedious handling techniques in order to obtain a unidirection-ally aligned and uniformly spaced set of whiskers in the metal matrix. 2) Due to weak interfacial bond strengths or because of the formation of additional embrittling phases at the metal-fiber interface during long-time exposure or fabrication at elevated temperatures, many composite systems have exhibited considerably lower strengths than those predicted by a law of mixtures analysis.&apos; These problems have been bypassed by the technique of growing whiskers and plates of high-strength materials in a ductile metal matrix by controlled unidirectional eutectic solidification.2 The tensile properties of directionally solidified A1-CuA12 eutectic are presented here. This alloy consists of a ductile aluminum matrix, containing up to 5.7 wt pct Cu in solid solution, which is amenable to precipitation hardening by heat treatment and a reinforcing high modulus CuAlz intermetallic phase. The two phases are present in the form of alternating platelets or lamellae. The microstructural stability of this unidirectionally solidified alloy at elevated temperatures has been studied extensively.3.4 and preliminary tensile and bend tests have been reported. 5-7In the present investigation the tensile properties of the A1-CuA1, eutectic have been studied as a function of several ther-momechanical variables: solidification rate. heat treatment. rolling at elevated temperatures. and lamellar orientation. It was felt that the uniformity of structure and excellent interfacial bonding would give tensile properties concomitant with the metal matrix composite theory of strengthening proposed by Kelly and coson. 8-9 The tensile properties that were obtained point to a wide distribution of strengths for the CuAlZ platelets, which leads to large deviations from the predicted mechanical behavior for this composite. EXPERIMENTAL PROCEDURE Epitaxial Growth of Eutectic Alloy. The A1-CuA1, eutectic alloy was prepared by an epitaxial growth process. Sections of a master alloy ingot (total impurity content <0.008 pct) were placed in an alundum boat, melted. and directionally solidified to obtain a multigrained plate 12 by 2 by 4 in. This plate was tapered at one end to mate with a seed crystal 1; in. long and 4 by $ in. square. Then the seed-plate combination was placed in an alundum boat which sat in a quartz tube passing through the center of a horizontal resistance wound tube furnace. A dried argon atmosphere was maintained. The temperature gradient in the furnace was such that the liquid-solid interface of the eutectic alloy was located near the end of the furnace and could be observed through the quartz tube. Single-crystal plates were formed by melting the material back to the midpoint of the seed crystal of the desired platelet orientation and then epitaxially growing the plate from the seed by withdrawing the alundum boat from the furnace at a constant rate. This technique was used to produce aluminum and CuA12 lamellae parallel and perpendicular to the transverse direction on the plate. Metallographic examination showed that both phases were continuous across the original liquid-solid interface. It was also possible to grow a plate from two seeds placed side by side: and, although the lamellae of one seed were oriented at 90 deg to those of the second seed, the interface between the two grains remained parallel to the growth direction along the entire ingot length. Maintenance of a straight intergranular boundary during the solidification process was possible as long as both seeds were oriented with their original growth direction parallel to the solidification direction of the plate. Eutectic plates were directionally solidified at rates of 0.2, 1.0. and 4.7 cm per hr and sectioned transversely to the solidification direction to determine the apparent inter lamellar spacing of the lamellae. Metallographic examination was also employed

Jan 1, 1970

By T. H. Ramsey, Richard Shield

A process has been developed for fabricating thin-film resistors that are compatible with integrated circuits. Films are produced by evaporation of single refractory metals using an electron beam heating source. Resistor paths are then made using standard photoresist etching techniques. A low-temperature coefficient of resistance is obtained by control of nucleation during deposition of the film. One application of the process has been the development of a discrete resistor used for current setting in linear integrated circuits. Multiple thin-film resistors were formed on oxidized silicon substrates using molybdenum metal as a source. An evaporated protective layer of SiO2 over the resistor prevents resistance changes which might occur during subsequent high-temperature processing. Properties of a typical resistor are as follows: R = 15.7 ohm per sq, tolerance surface dimensions = 0.028 by 0.028 in., stable after 4000 hr at 0. 75 w without heat sink. THIN-FILM resistors have been investigated for many years with a large selection of usable resistors resulting from a wide variety of materials. Many of the processes necessitate a high degree of complexity but in nearly all cases the conclusions have been that the materials used in each case were acceptable provided the deposition process was reproducible and could be controlled sufficiently to give the required tolerances. It is our opinion that simplicity is still the key to thin-film resistor fabrication. In this regard, the single metal is obviously the simplest process to control, provided all the necessary properties can be obtained. The idea is not original in this laboratory by any means. Others have taken this approach.&apos; It has been demonstrated that a fairly wide range of resistivities can be obtained by careful control of deposition parameters for any given metal, and by selection of several single metals a very broad range of stable resistors can be obtained. The transition from one metal to the next is made when a film becomes too thin for adequate process control or long-term stability. A great deal of emphasis is once again being placed on the thin-film resistor. Although they have been thoroughly studied in the past, new applications have been found that require the properties obtainable only from thin-film resistors. Integrated circuits, in general, are advancing toward higher speeds and radiation environments which require replacement of the present diffused resistors. Linear circuits in particular are requiring high-power, high-precision resistors for the more advanced applications. The particular requirements of some linear circuits are such that a discrete resistor is required. The resistor described in this paper was developed as a 15.7-ohm precision discrete resistor for use in a current regulating circuit requiring a +2 pct end of life overall tolerance, a dissipation of 750 mw, and the ability to operate over a fairly broad temperature range (i.e., a low temperature coefficient of resistance, TCR). State-of-the-art integrated circuit and silicon processing technology lends itself well to the fabrication of thin-film resistors. Not only is the resistor thin film well-suited to integration on individual circuits, but the oxidized silicon surface provides one of

Jan 1, 1969

By Lloyd B. Underwood

Dr. Gardener, in Chapter 2, has presented a comprehensive state-of-the- art review of site investigations For tunneling. Nearly all of the techniques he discussed will also be required for future site investigations. Therefore, this chapter will be devoted to a few rather new exploration techniques plus ideas for improving some of the present-day methods. In March 1962, the first symposium on "Remote Sensing of Environment" was held at the University of Michigan.l Since that time, four additional symposiums have been held at the same University. Also, the technical Literature has recently included a number of articles on remote sensing techniques. A recent one appeared in the February 1968 issue of Materials Research and Standards.Vt was entitled "Developments in Remote Sensing Applicable to Airborne Engineering Surveys of Soils and Rocks," and was written by Dana C. Parker. Mr. Parker predicts that aerial reconnaissance will someday supplant soil augers, rock drills, surface reconnaissance, and geophysical surveys as the engineer&apos;s primary means of obtaining information about soils and rocks. He states, "The engineer wishing to survey a route or a site or to locate rock and soils suitable for construction projects will be able to push some buttons in an airplane and record all the data required for determining the relevant conditions. In a short time after he returns to earth with his rolls of film and charts, he will be able to reduce and analyze the data by partially computerized techniques and to compile a concise and comprehensive engineering report that gives all the relevant information about rocks, soil, water, and vegetation in the area he surveyed. Most important he will feel as confident with his recommendations, derived primarily from image characteristics and spectral power distributions, as his predecessors did with recommendations based on more tangible evidence obtained from drill cores and surface reconnaissance." The airborne sensors for engineering surveys of soils and rocks are those that sample some electromagnetic property of the materials that com- prise the terrain and cover its surface. In addition to cameras, these include

Jan 1, 1970

By C. H. Cheng, C. E. Birchenall

The fundamental problem in the thermodynamics of solid solutions is the determinatiorl or calculation of the activities of the components as a function of temperature and composition. Since the theory of metals is not suficiently developed to allow a priori calculation of these quantities, they must be obtained from experiment. C. Wagner1 has reviewed the literature of this subject for the period before 1940. Although several important and extensive studies have been made in the meantime, the number of systems to which any sort of quantitative information can be assigned is vanish-ingly small. These data have become of great potential importance in studies of the structure of solid solutions2 and intermetallic compounds, the nature of the diffusion process,3,4 and perhaps even the mechanism of mechanical deformation.5 For these reasons, it. seems very worthwhile to extend the experimental data in this field. Although there is little use in duplicating Wagner&apos;s review, attention should be directed to the most recently reported investigations. A brief enumeration of the methods of measurement previously employed also should be valuable. The most direct method is the determination of the partial pressure of the components in the vapor phase in equilibrium with the solution. Both equilibrium and kinetic methods have been tried in metal systems, but almost exclusively on liquid phases. Only in the ease of carbon in iron alloys and in the copper-zinc system have extensive measure- ments been made which include solid phases. When one of the components is an element, such as nitrogen or carbon, which forms compounds which are very volatile and stable at normal temperatures and pressures (CH4, Co2, CO NH3), it is frequently possible to equilibrate mixtures containing these (such as CH4-H2, CO2-CO, NH3-H2) independently with the elernents (C, X) and with the metal (Fe, Ni, etc.). Such measurernents have been made for carbon in iron, iron-silicon, and iron-manganese alloys by Smith6 and in iron and iron-nickel alloys by Toensing.7 Differences between carbon activity values at the same temperature and carbon content when carboil is introduced from CH4-H2 rnixtures or CO-CO. mixtures indicate that the effects of hydrogen and oxygen in the system are not negligible, and one can only hope that the true value lies somewhere between these sets of results, probably nearer the CH4-H2 data since hydrogen is less soluble in iron than oxygen. This is essentially an equilibrium method, although flowing gas is employed. A kirletic method has been employed which consists of sweeping an inert gas (generally hydrogen) over the alloy at a series of rates, condensing the metal vapor out,, and analyzing it. The metal content can be extrapolated to zero flow rate (equilibrium). Wejnarth&apos;s8 work on Cd-Mg and Zn-Mg is a good example of this frequently used method. A variant of this consists of equilibrating a known volume of inert gas with the alloy, sweeping it out quickly, and analyzing for metal. In common with the above method, it has the disadvantage that the "inert" gas is generally somewhat soluble in the alloy. Moreover, the former continuously displaces the system from equilihrium and may give low values if solid diffusion is involved. The dew point method applied by Hargreaves9 to the alpha and beta brasses and by Schneider and Stolll0 to A1-Zn avoids the introduction of another component to the system, but is useful only in systems in which one component is much more volatile than the other. The alloy sealed in one end of an evacuated silica tube is heated to the desired temperature. The temperature of the other end is lowered until droplets of the volatile component condense. When the temperature is raised slightly, the droplets will evaporate. By careful adjustment of temperature, the range between evaporation and condensation can be narrowed appreciably. An independent determination of the vapor pressure of the . pure volatile component is necessary to give the partial pressure over the alloy. This is the method employed here to determine the vapor pressures of zinc and cadmium over their silver alloys up to 34 pct in cadmium and 76 pct in zinc. The former involves only the a solid solution, but the latter covers the a, ß, y, and e fields. In recent determinations, Herbenar, Siebert, and Duffenbarkl1 used the

Jan 1, 1950

By Ralph H. Sweetser

IN the recent world-wide deflation of commodity prices the coal industry, including both anthracite and bituminous coal, had reached a level where the actual delivered market prices received by the operators were usually less than the cost of production. Many steel companies and public utilities, operating their own "captive" mines, could have bought coal during the past three years for less money than the true cost of coal produced at their own properties. Competition within the coal industry itself was cruel to the point of profitless operation, and the competition of other forms of fuel was bearing heavily on the coal producers. They were thus forced into methods of production and utilization that they had hitherto ignored; there had been almost complete absence of any appreciation (by the bituminous operators especially) of the necessity of real research work in finding better methods of preparing coal for specific uses, and in finding new and profitable uses for different kinds and grades of coal.

Jan 1, 1933

By C. N. Kravig

STANDARD raises at Homestake are 150 ft long. Raises of more than 150 ft, driven with the use of a cage and hoist, are considered long raises- some have been driven more than 900 ft. Long raises have eliminated the need for access drifts on each level when transfer and ventilation raises are driven. These timbered cage raises, 7x9 ft in cross section, include a rock compartment and a combination cage, pipe, and manway compartment. To prevent excessive weight on the timbers, 10x10-in. bearing beams are cemented into hitches cut in the rock at 150-ft intervals. The beams also hold back timber movement caused by daily drawing of rock through the rock compartment.

Jan 6, 1957