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By D. H. Baldwin, R. E. Reed-Hill

DURING the course of experiments involving oxygen equilibrations with a high-purity Pd-5 at. pct Rh alloy, the appearance of a subscale was noted. Most of the heat treatments in a pure oxygen atmosphere were performed at 900°C. The presence of the subscale was noted when the oxygen partial pressure was in excess of approximately 95 mm, up to 1 atm, the highest pressure used. According to available thermodynamic information' on the free energy of formation of Rh2O3 (the only reliably reported solid oxide of rhodium), this oxide should not be stable under these conditions, nor, of course, any oxide of palladium. Extraction of the subscale from the matrix was affected by treatment with aqua regia, and the resulting X-ray diffraction powder pattern is shown in Table I. This pattern is not that of Rh2O3, nor that of any known rhodium or palladium oxide. It can be indexed on a hexagonal lattice with a. = 5.22Å and co = 6.0Å. In addition to this unknown material, there was a weak Rh2O3 pattern. An X-ray fluorescence analysis of the powder gave 3214 palladium counts per sec and 5381 rhodium counts per sec, thus indicating the likelihood of a double oxide of palladium and rhodium. In view of the fact that the above result was obtained on a single sample, it is perhaps best not to insist upon the above ratio of about 0.6, but possibly to tentatively assume 0.5 or 1/1. The small amount of Rh2O3 in the X-ray pattern might have occurred on cooling, and it seems possible that the double oxide, below some temperature level, is not as stable as Rh2O3. To examine this point, some of the extracted double oxide was heated on a sheet of pure palladium in air at 900°C, and allowed to furnace-cool over a period of several hours. The X-ray diffraction pattern of the powder showed approximately the same intensity of Rh2O3 and the "hexagonal" oxide as before, but, in addition, a rather faint pattern of another crystalline species made its appearance. This finding again suggests partial transformation of the major (double) oxide to other oxides on cooling from 900°C. Application of the phase rule shows that only one equilibrium oxide (subscale) could have been present at temperature. Vacuum-fusion, oxygen analysis of the extracted subscale showed 7.7 ± 0.7 pct O. Combining this information with that of the X-ray fluorescence analysis suggests the formula PdRhO. This compound should have an oxygen content of 7.07 pct, which is within the range of error of the oxygen analysis. However, until a more careful stoichiometric study is made, it is suggested that the formula be written

Jan 1, 1965

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

THE mechanism by which the super-saturated solid solution of 20 per cent silver in aluminum decomposes has been reported in two previous publications. 1,2 The analysis of streaks in Laue photograms showed that thin platelike particles (the so-called Guinier-Preston aggregates) form upon {111} matrix planes in the early state of decomposition.1 The size of these particles is larger, the higher the temperature at which they form in accordance with nucleation theory;3 at all temperatures they increase in size with aging.2 When they have grown thick enough to afford three-dimensional diffraction, powder X-ray photograms show that the structure is not that of the equilibrium precipitate y but that of a transition lattice ?'. Since this is also platelike in shape and also lies upon the {111} matrix planes with the {110} direction in the matrix parallel to the {11.0} direction in ?', it seems likely that the original platelet particles are merely ?' in an early stage of formation, and thus finely dispersed. The atomic spacing and pattern on the {00.0} plane in ?' are identical with those on the {111} matrix plane to which it lies parallel, and since comparable directions in the two planes are parallel, the lattices are thus coherent at the interface; an analogous coherence has been found in aluminum-copper alloys.3 The structures ?' and y are both close-packed hexagonal and are oriented alike; they differ only in interatomic distances. Consequently, ? ' is regarded as y strained from its ordinary dimensions by the lattice coherency between it and the matrix.2 The lattice movements that transform the matrix to the equilibrium precipitate appear to be very simple.2 The mechanism of precipitation in this system is simpler and is more precisely known than that in any other system,2,4 hence the system should be a profitable one for the difficult task of correlating property changes with structural alterations. The present report provides additional studies on powder X-ray diffraction from alloys of 10 per cent, 20 per cent and 30 per cent Ag, and presents the correlation of crystallographic changes with changes in microstructure, Brinell hardness and electrical resistivity of the three alloys. PREPARATION OF SAMPLES AND EXPERIMENTAL PROCEDURE The preparation of the 20.2 per cent Ag alloy has been described.2 Alloys containing 9.9 and 29.7 per cent Ag were prepared from 99.97 per cent Al and 99.99+ per cent Ag using a similar procedure. Rolled

Jan 1, 1943

By William J. Gillich, Gerald L. Moss

PREVIOUS studies of the shock loading of randomly oriented polycrystalline aggregates have firmly established that, after rather short load duration, hydrostatic compression closely approximates the shocked state.' However, McQueen deduced from pressure measurements with good time resolution that, during shock loading, metals begin to undergo a stress relaxation at the yield stress. He suggested that the relaxation is due to plastic deformation accompanying the change from a one-dimensional compression to a three-dimensional, hydrostatic, compression.' Stress relaxation may occur faster as stress is increased above the yield stress, but the existence of unidirectionally compressed states for finite times suggests that the concept of a unidirectionally distorted lattice should furnish considerable insight into the mechanical behavior of materials subjected to shock loading. Here, a crystallographic analysis is presented for the hypothetical situation where atom motion may be considered as unidirectional which, as indicated above, is a useful extension of the macroscopic concept of shock loading to the microscopic domain. Only motion caused by the com-pressive forces is treated; i.e., lattice vibrations upon which this motion is superimposed, as discussed by Fitzgerald, are ignored.3 The purpose of the analysis to be presented is to develop a description for single crystals of the lattice rotations that occur for idealized uniaxial strain deformation. The usefulness of such an analysis in realistic deformation is to give a method of specification of those properties of an initially distorted lattice which would affect the subsequent deformation. Non-axial complications that arise experimentally, such as off-axis rarefaction waves, must be treated in proper context. Consider the material element shown in Fig. 1 and let the compression be uniform at all regions of the element. Then, any interior point of the element is displaced in proportion to its distance from the base of the element. Accordingly, if the top of a unit element is displaced by an amount, (-K), with respect to the base, a point P(X, Y) will be displaced by (-KY). Crystal planes are, therefore, rotated by the compression. Analysis of this rotation may be accomplished from the geometry shown in Fig. 1 where the line OP is the edge of the plane {hkl} and N is its normal. The orientation of the crystal plane with respect to the shock direction is specified by the angle, before deformation. After deformation the edge of plane {hkl}

Jan 1, 1969

By William E. Ford, Edward Salisbury Dana

General Principles of Optics Optical Instruments and Methods General Optical Characters of Minerals 1. Diaphaneity 2. Color 3. Luster Special Optical Characters of Minerals belonging to the different Systems A. Isometric Crystals B. Uniaxial Crystals General Optical Relations Optical Examination of Uniaxial Crystals C. Biaxial Crystals General Optical Relations Optical Examination of Biaxial Crystals 306. Before considering the optical characters of minerals in general, and more particularly those that belong to the crystals of the different systems, it is desirable to review briefly some of the more important principles of optics upon which the phenomena in question depend. For a fuller discussion of the o tics of crystals, special reference is made to the works of Groth (translation by Jackson), Liebisch, Mallard, Duparc and Pearce, Rosenbusch (translation by Iddings), Iddings, Johannsen, Winchell, mentioned on p. 3 also to the various advanced text-goks of Physics. 307. The Nature of Light. - Light is now considered to be an electro- magnetic phenomenon due to a periodic/variation in the energy given off by vibrating electrons. This energy is transmitted by a series of periodic changes that show all the characters of ordinary wave phenomena. The light waves, as they are commonly called, possess certain short wave-lengths that are of the correct magnitude to affect the optic nerves. Other similar waves with longer or shorter wave-lengths belong to the same class of phenomena. Immediately beyond the violet end of the visible spectrum come the so-called "ultra- violet" waves with still shorter wave-lengths and on beyond these we have the X-rays and the "gamma" rays produced by radium. Of the waves having greater lengths than those of light waves we have the waves that give

Jan 1, 1922

By G. A. Crowe, W. T. Bishop

WHILE the literature in the United States on general polarographic technique is extensive, very little appears to be directly applicable to the analysis of flotation tailings. For this reason, it seemed worth while to present a few polarographic methods of ore analysis that have been in constant use in the laboratories of the Hercules Experiment Station for the past few years. At the time of our initial investigation of the polarographic method, there was little or no mention of its specific application to flotation tailings. It was therefore necessary for us to establish suitable conditions for the analysis of our flotation tailings and to consider possible interfering constituents. The polarograph, or dropping mercury electrode, method was discovered in 1925 by J. Heyrovsky and M. Shikata,1 of the Charles University, Prague. This method has since received extensive development and the literature contains many articles on the use of the polarograph for the quantitative determination of metals as well as anions, oxygen in solution, and reducible organic compounds. Kolthoff and Lingane,2 by the publication of their book, "Polarography," in 1941 did much to advance the knowledge and use of the polarograph. In chapter 25 of that book, methods for the polarographic analysis of brass, steel and iron products, alloys, and zinc ore are given. Aluminum,3 cadmium,3.4 cobalt,4 copper,3-9 gold,10 iron,3,11 lead, 3,12,13 molybdenum," nickel,4.8,9 tin,15 and zinc3,4,5,7 in ores have been analyzed by the polarograph. However, most of the work on tailing samples has been published in Russian journals and translations are not yet readily available. In this paper we will describe the method that was developed and used in our laboratory for the determination of copper, zinc, and lead in flotation tailings. PRINCIPLE OF THE METHOD The polarograph is an instrument for applying a potential to a mercury pool and a dropping mercury electrode separated by a solution, and for measuring the resultant electrical current. The procedure is essentially a small-scale electrolysis, in which the voltage required to reduce or oxidize the material identifies it qualitatively and the current measures the concentration quantitatively. Different constituents in a sample may often be determined simultaneously provided they reduce at sufficiently different voltages. An example is the determination of copper and zinc in the same solution. The reduction potentials are quite far apart, as shown in Fig. I. The polarographic method is particularly useful in the range of concentration between those normally determined by spectographic and chemical methods. In

Jan 1, 1946

By A. S. Richardson

AIR conditioning, or air cooling, for the improvement of ventilation in the Butte mines has come into increasing use during the past 10 years. In part, the methods practiced have been described in previous publications of the Institute, but some improvements on earlier methods have been made and a number of new features have been developed. This paper is presented as a record of progress made, and for the sake of completeness describes all general features of the work. The need for air conditioning in the ventilation of mines in the district arises from the fact that the temperature of the ground and mine water has shown a very great increase with increase in mining depth, and has now reached a maximum of slightly over 130ºF. The most difficult part of the ventilation problem is the maintenance of temperature and humidity of a satisfactory standard in the working places, especially on the lower levels. Although ordinary ventilation is adequate to maintain good conditions in most of the working places it is subject to a number of limitations at great depth. Most important among these limitations is that with increase in depth the air becomes heated before it reaches the working places, both by compression from increase in atmospheric pressure and by heat transferred to it from rock at high temperature, so that its capacity for lowering temperatures is greatly reduced before it reaches the operating zone. Increasing depth of mining also increases the distance traveled by the air in its passage through the mine, and this causes a corresponding increase in resistance to air flow, so that there is greater difficulty in maintaining even the same volume in circulation. Thus, in the face of a demand that the ventilating system have a very much greater capacity to remove heat from the mine, the tendency is for that capacity to diminish. The only evident alternatives were (I) the opening of additional air shafts to increase the volume of air in circulation, (2) an extension of the existing system that would be subject to the same limitations, or (3) the adoption of an entirely different method such as air cooling. Fortunately for an economic solution of the problem, the mean annual temperature of the surface atmosphere at Butte is about 40°F., with very low relative humidity in summer, so that there is unlimited natural cooling power at a temperature range adaptable to air-conditioning methods. METHODS Two similar methods of air conditioning are used, as necessitated by service requirements and dependent upon the equipment available. In one, which is the more important and has the greater cooling capacity, water is circulated in a closed circuit, and, alternately, first absorbs heat from warm mine air and then dissipates it in the surface atmosphere by cooling at a cooling tower. The second

Jan 1, 1941

By Kenneth Robertson

THERE is probably less known of this subject than of any other connected with the metallurgy of iron. In all the books that treat of this matter, there ore given analyses of slags, their chemical formulae, the loss of iron, etc. ; but few, if any, give the character of the iron mode at the time; none give analyses and physical characteristics of the ores and limestones used, and they present merely isolated examples from various furnaces, and consequently one is more frequently puzzled than enlightened after reading them. During two years I have had occasion to analyze the slags and many of the pig-irons from two furnaces, and for this article I hove made analyses of all the different grades of pig mode by them. A

Jan 1, 1873

The mining companies on the page opposite are among the elite industrial 500 in Fortune magazine's June Directory of U. S. firms that rang up the largest dollar sales volume in 1967. The companies are listed according to their 1967 sales rank, which is given along with their 1966 rank for comparison. Mergers played an important role in the addition and deletion of several companies to the list. Tenneco, Occidental Petroleum and Gulf & Western Industries made the list of mining companies by their purchases of Kern County Land, Island Creek Coal, and New Jersey Zinc, respectively. In turn, these three companies disappeared from the list. General Aniline & Film acquired Ruberoid, and Ideal Cement is now a part of Ideal Basic Industries -a name change only. Only two companies, St. Joseph Lead and U.S. Smelting, Refining & Mining, were actually displaced from the list. The mining industry increased its sales 14.5%, placing fourth among the 22 industrial classifications listed in the Directory. However, among the ten biggest losers in sales were four mining companies-Kennecott Copper, -33.8% ; Asarco, -21.8% ; Amax, -16.5%; and Anaconda, -15.1%.-which was mostly a result of the copper strike, except for Amax which suffered strikes at its molybdenum and aluminum operations. Mining heads the list of industries for return on sales and assets per employee, while it rests at the bottom with respect to sales per dollar of invested capital.

Jan 8, 1968

By E. H. Rennhack, J. F. Libsch

Definite transition behavior was found in unalloyed titanium at 0.13 pct 0 equivalent. The addition of 0.5 Sn, 1.0 Al, 0.5 Al, and 1.0 Sn lowers the tvansition temperature of titanium at oxygen equivalents exceeding 0.22, 0.29, 0.40, and 0.51, respectively. Metallographic evidence indicates that progressive amounts of oxygen restrict deformation at low temperatures resulting eventually in brittle fracture. The presence of tin or aluminum is thought to alter the atomic distribution of oxygen within the titanium lattice in such a manner as to facilitate some degree of slip and twinning. 1 ITANIUM-like iron and zinc experiences a transition from ductile to brittle fracture with decreasing temperature. The presence of sufficient quantities of the interstitial elements, carbon, oxygen, and nitrogen in solid solution, has been shown to progressively lower the room-temperature impact resistance of titanium with increasing interstitial content.1"1 Ogden,et al,2 reported finding no transition from ductile to brittle fracture with decreasing temperature in iodide titanium. However, a definite transition was found to occur at 0.36 pct 0 equivalent in an alloy containing 0.47 pct carbon in solid solution. The oxygen equivalent in this case was obtained by assuming the effects of carbon, oxygen, and nitrogen in combination on the impact properties of titanium to be additive on the same basis as their separate effects on tensile strength, namely: Oe = 2/3 (pct C) + pet 0 + 2 (pet N) They concluded that the tendency toward transition behavior is dependent on the total interstitial content in solid solution and not on any one particular interstitial element. Rennhack,4 however, recently found transition behavior in iodide titanium at an oxygen equivalent of 0.17 pct. Ogden, etal3, reported that the strengthening effects of carbon, oxygen, and nitrogen in titanium decrease with the addition of tin. They showed that tin additions increase the tolerance of titanium for the interstitials, that is, 10 pct Sn permitted individual additions of up to 0.4 wt pct of the interstitial elements without any significant loss in ductility. Aluminum tends to decrease ductility and impact strength of titanium for a given interstitial ~ontent.3 Van Thyne and Kessler5 found that the solid solubility of carbon in titanium doubled in the presence of 10 pct Al. The precise effects of tin and aluminum in the nrespncp of rorvfen nn the impact properties of titanium had previously not been determined. The high oxygen tolerance of titanium containing tin may provide a suitable means for improving the impact properties of titanium containing the interstitial elements, particularly oxygen. Unlike tin, however, aluminum has a high affinity for oxygen and will reduce rutile titanium dioxide (TiO2)by a thermit-type reaction.6 Thus, the atomic distribution of oxygen in titanium might be different in the presence of aluminum. The present work was undertaken to: 1) Determine the effect of oxygen on the transition behavior of unalloyed iodide titanium. 2) Determine the effect of small amounts of tin and aluminum on the transition behavior of iodide titanium in the presence of oxygen and other interstitial~. EXPERIMENTAL Three different lots of iodide titanium were employed to prepare the alloys studied in the present work. Their chemical composition is presented in Table I. The compositions of the tin and aluminum used for alloying are shown in Table 11. Oxygen additions were made using calcined rutile titanium dioxide (TiO2)of 99.7 pct purity. Alloy Preparation—Four titanium-base alloys containing separate additions of 0.5 and 1.0 pct each

Jan 1, 1960

[Officers JOHN CHIPMAN, President W. R. HIBBARD, JR., Past President C. C. LONG, Vice President T. D. JONES, Treasurer R. W. SHEARMAN, Secretary D. C. JOHNSTON, Assistant Secretary]

Jan 1, 1961

By Albert Sauveur

My first paper dealing with the theories of the hardening of steel by rapid cooling was published in the Transactions of this Institute in 1896— 30 years ago-under the title "The Microstructure of Steel and the Current Theories of Hardening," hence, also, the title of the present paper. It was extensively discussed and was, I believe, one of the starting points of many subsequent papers and discussions of the same subject, dis-cusssions which at times became almost violent and which led to the formation of different schools such as the "Carbonists" and the "Allo-tropists." Some of the older members of the Institute, who took part in the debate or who were interested observers, will, I am sure, have kept a vivid remembrance of it. The controversy gradually quieted down, apparently for lack of ammunition, without any side acknowledging defeat. Recently, however, interest in it ha been revived through the claims of some that these vexed questions had at last been solved. In an effort to ascertain if possible the prevailing view of those best qualified to express an opinion a questionnaire was submitted to the following gentlemen: J. 0. Arnold Sir Robert Hadfield Edgar C. Bain W. H. Hatfield Carl Benedicks Samuel L. Hoyt N. Belaiew Kotaro Honda H. M. Boylston Zay Jeffries Harry Brearley H. Le Chatelier G. K. Burgess H. H. Lester William Campbell Francis F. Lucas H. C. H. Carpenter John A. Mathews Pierre Chevenard A. McCance P. Dejean Albert Portevin C. A. Edwards Walter Rosenhain F. Giolliti Bradley Stoughton G. Grenet F. C. Thompson Leon Guillet

Jan 1, 1926

By Kenneth Robertson

THEREi9 probably less known of this subject than of any other connected with the metallurgy of iron. In all the books that treat of this mattes, there are given analyses of slags, their chemical formulae, the loss of iron, etc. ; but few, if any, give the character of the iron made at the time ; none give analyses and physical characteristics of the ores and limestones used, and they present merely isolated examples from various furnaces, and consequently one is more frequently puzzled than enlightened after reading them. During two years I have had occasion to analyze the slags and many of the pig-irons from two furnaces, and for this article I have made analyses of all the different grades of pig made by them. A

By E. A. Gulbransen, K. F. Andrew

The vacuum-microbalance method was used to study the oxidation behavior of Zircaloy-2 and -3A over the temperature range of 300 to 850°C and at 0.1 atm pressure. The results fit in well with the authors' earlier studies on zirconium. Tin was found to increase the rate of oxidation and also the temperature at which the metal burns. Both the cubic-rate law and the parabolic-rate law gave imperfect fits to the rate data. Since the parabolic-rate law has been derived from accepted physical principles, this rate law was used to interpret the rate data. A heat of activation of 28,600 cal per mole was calculated. The transition phenomenon previously observed in hot-water and steam-corrosion processes was studied systematically for oxygen atmospheres. Observations on the rate of oxidation, color and properties of the oxide films show that the transition phenomenon was associated with a failure in the adherence of the oxide to the alloy. ZIRCALOY-2 and -3A have found important uses in the field of reactor metals due to their low neutron adsorption, good strength and good resistance to corrosion. One feature of the corrosion reaction in steam or hot water is the sharp transition in the rate of corrosion to a higher value after a certain amount of reaction has occurred. This paper presents a study of the reaction of Zircaloy-2 and -3A with oxygen including a study of the transition phenomenon which has been found to occur also in oxygen atmospheres. A comparison will be made between the oxidation behavior of these alloys and the pure metal. It was hoped that a study of the details of the oxygen reaction would lead to a better understanding of the reactions occurring in hot-water and steam atmospheres. Literature Kinetics-—The reaction of Zircaloy-2 and -3A with hot-water and steam atmospheres has been studied by Thomas.' Goldman and Thomas,' Thomas and Forscher," and Thomas and Kass.' Empirical equations for the kinetics of the reaction have been given by Thomas and Forscher." The change from the initial slow rate of reaction to the final rapid rate of reaction has been termed transition with the post-transition corrosion kinetics following a simple linear equation in time. The corrosion behavior in high-temperature steam was similar in many features to the corrosion in high-temperature water. Goldman and Thomas' and Pray and Peoples' have shown that the addition of tin, while increasing the rate of corrosion, counteracts the deleterious effect of nitrogen. The beneficial effect of iron, nickel and chromium was to improve the adhesion of the oxide to the metal as well as to counteract the deleterious effect of nitrogen. Mallet and Albrecht" have studied the oxidation of two zirconium-tin alloys. The cubic-rate law was found to fit the oxidation data for the 1.5 pct tin alloy while the parabolic-rate law was found to fit the data for the 2.5 pct alloy. Kendall' in a recent paper has studied the oxidation of Zircaloy-2 containing 1.5 pct tin in air atmospheres. Transition Phenomenon—In steam atmospheres Thomas' has observed fora 1.8 pct tin alloy containing small amounts of iron, nickel and chromium that transition to a more rapid rate of corrosion at 400°C

Jan 1, 1959

SINCE I told you in the preceding chapter how the potter's art is followed in practice, now in this following one I wish to tell you how mortar* and bricks are made, and how and to what purpose they were discovered, although I know you will answer that you know it, inasmuch as it is an art known not only to skillful men but also to the unskilled ones by whom it is practiced, and that bricks and mortar were made and always will be made for the purpose of building. This I admit, but probably everyone does not know it as you do, and you perhaps, do not know its beginnings, although I remember having told you of them. Wishing to repeat it better now I shall begin with long ago, so that both you and I may be better satisfied. Therefore I tell you that you should know that all the arts that men practice in the world have been learned by them either through the process of reasoning from the principles of natural phenomena, from the actions of animals, by chance, or when forced either by some necessity or

Jan 1, 1942

By Victor A. Phillips

A series of strips of a Ni-12.7 at. pct A1 alloy were Prepared containing cubical y'(NisAl) precipitates with edge lengths from 60 to 500A. A particle-free solution-tveated strip was included for cornparison. They weve cold-rolled 95 pct and the effects of particle size on the isochronal (1/2 hr) annealing behavior between 300° and 950°C studied (by hardness and light and electron microscopy). It ulas inferred that the particles deformed with the lnatvix becoming lamellae which remained coherent. Comparison with published data fov pure nickel showed that aluminum greatly re-tavded softening and recrystallization, but it made little difference whether or not particles were present. The presence of pakticles led to a heterogeneous distribution of precipitates after annealing at 700" to 750°C. Recovery was not detected. Recrystallization occurred by the growth of new grains into unrecrys-tallized material. In a previous study by the author,' the growth of Ll2-type ordered yl(Ni3Al) precipitates was followed in Ni-12.7 at. pct A1 alloy as a function of aging at 600" and 700°C. The particles were showo to be cubical in shape in all sizes from 50 to 3000A and remained coherent. This work was used as a guide in preparing the starting structures for the present study of the effect of these particles on the annealing behavior of heavily cold-rolled strip. Another question of present interest was whether dislocation and particle hardening were additive, since the structures before rolling ranged from solution-treated to peak-aged to overaged. Also, precipitation might occur on annealing after cold-rolling. Reference may be made to other papers2"5 for previous work in this relatively unexplored field and only some recent work will be mentioned her:. phillips2 studied the effect of deformable 0 to 590A-diam cobalt particles on a Cu-3.23 pct Co alloy rolled 95 pct and found that the particles, which rolled out into thin lamellae, impeded softening and recrystallization. Tanner and servi3 likewise studied the annealing of cold-swaged Cu-2 pct Co alloy containing 150A-diam particles and found impeding effects. Haessner et a1.,4 on the other hand, found that incoherent 2-p-diam non-deformable particles of B4C (0.04 vol pct) tended to increase the rate of recrystallization of copper rolled up to 95 pct reduction. They attributed this to the formation of new grains at the particle interfaces. Humphreys and artin' found that nondeformable silica particles in copper rolled to 30 pct reduction accelerated recrystallization if the particle spacing was large and retarded it if the spacing was smaller. Haessner et a1 4 also studied a rolled Ni-Cr-A1 alloy; however, the particles of y'(Ni3Al)-type precipitate were not put in before rolling, but separated during the isothermal annealing at 750°C. No previous work appears to have been carried out on the effect of y' (Ni3A1) particles on the annealing of Ni-A1 alloy. Hornbogen and ICreye7 redetermined the solubility c of aluminum in nickel as a function of temperature T and showed that it was given by c = 32.6 exp(-1940/RT). This relation gives aluminum solubilities of 15.1, 14.2, 12.0, and 10.7 at. pct at 1000°, 900°, 700°, and 600°C, respectively. The phase precipitated from the nickel-rich solid solution is fcc y1 (Ni3A1) which has a Cu3Au -type ordered structure8 and remains ordered up to 1000°C.B EXPERIMENTAL PROCEDURE The alloy used was identical with that used before. Chemical analysis showed 6.27 wt pct (12.71 at. pct) Al, the principle impurities being 0.065 pct Fe, 0.022 pct Co, 0.020 pct Cu, and 0.004 pct C. Bar stock of 1 in. diam was cold-swaged to % in. diam, cold-rolled to 0.300-in.-thick strip, and annealed at 900°C in dry hydrogen. It was cold-rolled to 0.100-in. thickness and solution-treated for 1 hr at 1000°C while sealed in a quartz tube in argon, quenching in iced brine with the aid of a device to snap off the nose of the tube. Lineal analysis gave an average grain size of 0.055 mm. Pieces of strip were aged at 700°C in vacuo for 30 min, 51/4 hr, and 1 week to produce nominal average particle widths of 60, 150, and 500A, respectively, as known from the previous work.' The average diamond pyramid hardness was determined. The heat-treated strips were rolled from 0.100 to 0.005 in., a reduction of 95 pct, and the rolled strips stored at about -5°C. Small pieces were annealed within 1 week for 30 min at temperatures from 300° to 950° ±2°C in a horizontal vacuum furnace. Strips were withdrawn into a cooling zone, giving an estimated initial cooling rate from 950°C of about 50°C per sec. Average diamond pyramid hardnesses were determined on a lightly electropolished spot on the surface of each strip using 300-g load. Each point on the softening curves represents a separate annealed specimen. Sections containing the rolling direction were examined by optical metallography. Selected specimens were electrothinned to the center plane' and examined by transmission at 100 kv in a Siemens Elmiskop I electron microscope. It is well-known that changes in the structure tend to occur when a deformed strip is electrothinned below a thickness of a few hundred angstroms, although this is less serious with a material such as nickel which has a high melting point, and also is apt to be less serious when particles are present. Observations were nevertheless confined to thicker regions of the foils with estimated thicknesses over 1000A. No changes were observed due to beam exposure.

Jan 1, 1968

By C. P. Gazzara and

The modulus of elasticity and yield strength of commercially pure, annealed titanium sheet was investigated at room temperature as a function of strain rate and direction of loading. The value of E varied with direction of measuremeni in the sheet but was unaffected by strain rate in the range 0.04 x 10-to 10-2min-1. The yield strength increased with increase it2 strain rate and varied with specimen orientation. VALUES of the modulus of elasticity, E, in tension for commercially pure titanium have been reported at from 14 to 20Xl06 psi.' Reasons suggested for this variation have been a) composition, b) strain rate, c) texturing, and d) creep. For example, alloys of titanium with aluminum, manganese, and nitrogen have yielded modulus values of from 12.5 to 16.8 x lo6 psi at room temperature.' It was shown by Klier that the modulus in titanium plate was sensi-tive to strain rate. while Dotson and kattus meas- ured variations in E as the strain rate was increased from 3X to 60 min-l. For RC-7OA, 0.040-in. titanium sheet at room temperature Dotson and Kattus found that the average values of E, for specimens in the rolling direction, increased from 14.7 to 16.0 X lo6 psi as the strain rate increased. Simultaneously, the 0.2 pct yield strength increased from 74,700 to 95,700 psi for the same specimens. Differences in yield strength and E have been reported as a function of directionality in titanium sheet.= Dotson and Kattus report such an effect, and Feola6 found in annealed titanium sheet marked anisotropy in tensile strength, yield strength, reduction in area and elongation at room temperature, with

Jan 1, 1961

By Walter Crafts, C. M. Offenhauer

IN a previous study' of the carbide phase of chromium steels, it was shown that chromium carbide (Cr7C3) is a more stable carbide than cementite (Fe3C) at tempering temperatures above about 500°C. in quenched steels containing from about r1to 7.5 per cent chromium. Below this temperature the carbide phase was found to consist of cementite in all of the steels examined. In the present investigation it was found that a similar change in the carbide phase takes place in molybdenum and in chromium-molybdenum steels at approximately the same tempering temperatures. The approximate ranges of occurrence of the alloy carbides Cr7C3, Cr4C, and Mo2C have been determined in steels containing up to 5 per cent chromium, 1 per cent molybdenum and 0.60 per cent carbon. The experimental steels were made in small high-frequency furnaces from Armco ingot iron, low-carbon ferrochromium and calcium molybdate and were poured into 2-in. ingots, which were forged to 1-in. round bars. Sections of the bars were heated to the carbide-solution temperature and cooled rapidly to induce austenite transformation at relatively low temperatures. The steels were subject to some segregation, therefore comparatively high temperatures were necessary to dissolve all of the carbides. The microstructure of the quenched specimens was examined to verify the belief that the carbides had been dissolved, and also to determine the nature of the nonmartensitic structure of incompletely hardened steels. Ferrite and pseudomartensite were present in some of the specimens, but all specimens were quenched at such a rate that pearlite was not formed, in order to ensure the formation of the carbides at temperatures lower than about 500°C. It had been found previously' that in chromium steels the chromium carbide could be produced by transformation of austenite in the pearlite range above 500°C., and, in order to start the tempering treatment with the carbide present as cementite, the absence of pearlite was considered to be essential. The specimens were tempered for 64 hr. to permit the formation of the stable carbide. After tempering, the specimens were submitted to microscopic and X-ray examination. The carbides were separated either electrolytically in a 5 per cent HCl electrolyte or with an acidified copper-potassium chloride solution. The crystal structure of the carbide phases was determined by the Debye-Scherrer type of X-ray patterns. The X-ray patterns obtained from specimens near the boundaries between two types of carbides were generally weak and diffuse as compared with the other patterns. For this reason, and because the more soluble components may be masked, the boundaries between the phases could not be determined precisely. However, the X-ray analysis of electrolytically separated carbides has given consistently reproducible results

Jan 1, 1943

THE problem of reaction rates in the open-hearth process is essentially that of trying to form a fairly clear picture of the "chemical mechanisms" in the bath. Quantitative data on reaction rates would perhaps not be of much practical importance even if they were available; however, what few approximate data there are can be used in combination with data given in Chapters 16 and 17 to sketch a picture of the "chemical mechanics" of the open-hearth process that is consistent with essentially all the present available evidence. The result may later be found incorrect in many details but even so it will illustrate certain useful methods for obtaining a clearer understanding of the process. Consistent with the treatment in Chapter 15, but in simpler terms, we may say that chemical reactions in general involve the following elements or steps : 1. The reacting molecules are mixed together in space in such fashion as to favor collisions among them. 2. Units of what is usually an intermediate molecular arrangement called an activated complex are formed at a certain rate, depending on temperature and concentrations. 3. .These activated complex units decompose into the reaction products (this step usually assumed to be so rapid as never to limit the over-all process). 4. In any of these steps, heat energy may have to flow into, or away from, the reaction zone to permit the reaction to proceed. 5. The products of reaction will usually have to move out of the way to permit further reaction. The temperature factor enters mainly through step 2, and its effect is very marked. (What is called temperature is really the mean energy content of all the molecules of the substance involved; at any one temperature a certain proportion of the molecules will have much higher energy content than the mean value.) Various reaction rates measured at around room tem-

Jan 1, 1964

By S. R. Goodman, Hsun Hu, R. S. Cline

The quenching technique has been used to study phase relations in the composition area 2FeO.SiO2-FeO-SiO2-MnO.Si02-ZMnO.SiO2 of the system iron oxide-manganese oxide-silica under strongly reducing conditions such as exist in a gas mixture consisting of equul parts of carbon dioxide and hydrogen. Liquidus and solidus temperatures of most mixtures in the composition area studied are in the range of 1173° to 1345°C. EQUILIBRIUM relations existing among the oxides of iron, manganese, and silicon are of particular interest in two areas of steelmaking: slags and ingot inclusions. Mixtures of these oxides represent about 90 pct of the slag in the acid steelmaking process, and so dominate the chemistry of the whole refining process. These constituents also play an important role in the early slags existing at the time of the "lime boil" in the basic open hearth process. If these slags are liquid, they "wet" the lumps of lime rising from the bottom of the bath, and react with them. A liquid slag rich in CaO is then formed at the very beginning of the refining. Because the temperature is still low, all conditions for a good dephosphoriza-tion are fulfilled at this stage of the operation. Metal deoxidized with ferromanganese or silico-manganese is likely to contain, as inclusions, phases made up from among the oxides of iron, manganese, and silicon. A knowledge of stability relations existing among the phases present in this system, therefore, enables one to predict the hardness of the inclusions encountered. Moreover, because the shape of the inclusions in steel has a profound influence on the physical properties of the metal, it is important to establish whether or not the oxidic material is present as liquid or crystalline phases during heating and rolling of the steel (-1150 to 1350°C). A knowledge of melting relations in synthetic mixtures of iron oxide, manganese oxide, and silica will give a clue to these problems. Methods for determining such relations and the results obtained are described iln this paper. I) PREVIOUS WORK A number cf previous studies have dealt with the three "binary"* systems bounding the system iron oxide-mangar,.ese oxide-silica. The system iron oxide-silica was studied by Bowen and shairerl in 1932. Their data were obtained by equilibration of mixtures in contact with metallic iron. Phase relations for the system iron oxide-silica ill atmospheres of different oxygen pressures car1 be derived from data on the system FeO-Fe2O3-SiO2 as determined by Muan.2 The diagram shown iri Fig. l is a section of this system in an atmosphere of CO2 and H2 in ratio 1:l. The system manganese oxide-silica has also been the subject of several investigations. Most of the early studies suffered from a lack of proper control of the atmosphere under which the equilibrations were carried mt. Phase diagrams for the system at two well defined levels of oxygen pressures have been determined recently. Glasser3 determined stability relations in an atmosphere consisting of carbon dioxide and hydrogen in ratio 5:1, diagram Fig. 2, and Muan4 studied phase relations in the system in air.

Jan 1, 1962

By Charles L. Mantell, Kurt Straler

The hydrogen reduction of Cr2O3 to chromium metal was found to be feasible at very low water-vapor concentrations, corresponding to dew points of -38° to -24°C, over a temperature range of 1130" to 1490°C. Hydrogen reduction under these conditions was predicted by the calculated equilibrium curves which also indicated that CrzOs is reduced directly to chromium without forming the intermediate oxide, CrO. This reduction path was confirmed by X-ray diffraction analysis. The percent reduction of Cr2O3 at each reaction temperature was constant with time, suggesting an inhibiting effect of water vapor. A small increase in the residual water-vapor concentration of a single temperature, 1490°C, strongly retarded the rate of reduction This effect was expressed by an empim'cal equation which indicated a direct relationship between "distance from equilibrium" and the rate of reduction. me effect of temperature over the range of 1130" to 1490°C was expressed in an Arvhenius plot of log rate vs reciprocal absolute temperature. From this curve the apparent enthalpy of activation was found to be 29,600 cal. Based on the hypothesis that the rate of reductiun is contvolled at the oxide-metal interface, an over-all rate equation consistent with the experimental data and the thery of absolute reaction rates was formulated. A simplification of this expression to an Arrhenius equation was justified by the overriding effect of temperature on the rate of reaction for the minimum water-vapor concentration range. MOST of the metals in Subgroup V1 of the periodic table can be prepared commercially by direct reduction of their oxides by hydrogen or carbon monoxide, at temperatures considerably below the melting points of both the metals and their oxides. Chromium is an exception, being generally reduced from its ore, Cr2O3 . FeO, by silicon in an electric arc furnace which operates above the melting point of the Fe-Cr alloy or above the melting point of chro- mium if a chromium oxide be the starting material. In reduction of chromium oxide by hydrogen, either reduction does not occur at all or the rate of reduction is extremely slow. Theoretical considerations based on the high, exothermic, free energy of formation of Cr2O3 compared to the oxides of the other Subgroup VI metals, molybdenum, tungsten, and uranium, would also suggest a slow rate of reaction and a high activation energy. Interest in the direct gaseous reduction of fine-powdered ores in fluidized beds was considered justification for examination of this reaction. In order to develop a basis for a continuing study of the commercial feasibility of the direct gaseous reduction of chromite, a study of the kinetics of the reduction of Cr2O3 with hydrogen was undertaken. To the authors' knowledge no accurate kinetic data for this reaction have been obtained. Neither has an activation energy been determined nor has an attempt been made to establish a mechanism of reaction. LITERATURE Maier10 compared the data of I. Y. Granaat,6 H. von Wartenburg and S. Aoyama, and G. Grube and M. Flad7 with that derived from calorimetric and ther-modynamic properties for the equilibria for the reduction of Cr2O3 with hydrogen. These results, plotted as the log of the equilibrium constant vs absolute temperature for the reduction of Cr2O3 and the intermediate oxide, CrO, to chromium, show agreement between the differently derived data. In both cases the equilibrium constants were extremely low. Maier showed that, over a temperature range of 1000° to 2000°K, Cr2O3 is more readily reducible than CrO. Granat assumed that CrO was preferentially formed from Cr2o3 above 1100°C. Grube and Flad's analysis of their reaction products in the 895" to 1000°C range indicated the coexistence of only Cr2O3 and chromium. The hydrogen reduction of the other Subgroup VI metals, molybdenum, tungsten, and uranium, shows that reduction of the higher oxide proceeds through all of the intermediate oxides before being reduced to the metal. Since evidence pointed to an anomaly in the reduction behavior of Cr2O3, the authors investigated the reduction path of Cr2Os.to chromium. This was done theoretically with more recently available free-energy data and experimentally by X-ray diffraction analysis. This work reinforces Maier's conclusion.

Jan 1, 1964