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By C. H. Li, S. H. Bendel, J. A. Sartell

Small additions of Mg to a 62 Cu-38 Ni alloy reduce the oxidation yates drastically between 500° and 850°C. Metallographic examination of the oxide scale disclosed a continuous network, identified by X-ray diffraction as (Ni, Mg)O solid solutions, located along the former alloy grain boundaries. This network acts as a barrier to diffusion. It is thought to result from the segregation of mg to the alloy grain boundaries. Oxidation occurs preferentially in these regions because of the presence of this more active element. To substantiate these ideas, homogenized alloys ulere oxidized. No oxide network was produced and oxidation rates were the same as for the parent 62 Cu-38 Ni alloy. An interesting aspect of the oxidation of the 62 Cu-38 Ni alloy previously described by the present authors, is the relationship between oxidation kinetics and changes in the microstructure of the oxide.' The oxide scale on these alloys consists of two layers: a thin layer of CuO outside a much thicker layer of Cu20 in which particles of NiO are dispersed. In addition, immediately beneath the oxide-metal interface there is an internally oxidized zone in which NiO particles are dispersed in a copper-rich alloy matrix. Experimental observations on the growth of the individual layers under isothermal conditions have led to the conclusion that the rate-determining step in the oxidation of this alloy is the diffusion of anions through the Cu20 layer. It has been found that this diffusion rate is increased by the recrystallization of the outer CuO layer. Willardson and Gorton have reported that the addition of magnesium to the 62 Cu-38 Ni alloy causes a decrease in the oxidation rate.2 The present investigation was undertaken in order to determine the mechanism by which magnesium additions improve the oxidation resistance of the 62 Cu-38 Ni alloy. EXPERIMENTAL PROCEDURE Fifty-gram ingots of Cu-Ni alloys were prepared by vacuum melting materials of 99.999+ pct purity. These ingots were then remelted in a He atmos- phere and magnesium added in the form of a previously prepared and analyzed Cu-Mg master alloy. This procedure was necessitated by the high reactivity of pure magnesium at high temperatures. The proportion of the alloying elements was adjusted so as to obtain alloys with the desired magnesium content while maintaining a Cu-Ni ratio of 62 :38 by weight. (All alloy compositions will be given in weight percent.) Since it was considered desirable to study the oxidation of only single-phase, solid-solution alloys, it was necessary first to determine the approximate limit of solid solubility of magnesium in the 62 Cu-38 Ni alloy. A series of melts with various magnesium contents was made, homogenized by annealing for 48 hr at 975OC, then cooled in the furnace. Metallographic samples were prepared, etched in a potassium dichromate solution and examined at XI500 for the presence of a second phase. The alloys were then chemically analyzed and it was found that the approximate limit of solid solubility of magnesium in the 62 Cu-38 Ni alloy was 1 pct Mg. The ingots containing less than 1 pct Mg (0.19, 0.29, 0.58, and 0.87 pct Mg) were cold-rolled down to thicknesses suitable for oxidation experiments and specimens for gravimetric studies were cut to dimensions of 3.0 by 1.5 by 0.05 cm, specimens for inert marker studies, 0.6 by 0.6 by 0.17 cm. These were heat-treated in a protective atmosphere at a temperature (975" C) well above the oxidation temperatures and furnace-cooled to insure structural stability of the alloy during oxidation. Immediately prior to oxidation, the specimens were chemically cleaned by immersion for 1 min in a solution of 2 parts nitric acid, 1 part acetic

Jan 1, 1961

By E. T. Hayes, A. H. Roberson, M. H. Davies

ZIRCONIUM has been produced on a pilot-plant scale for only a few years, but the potential uses have led a large number of research establishments to engage in a thorough study of the metal and its alloys. The work described in this paper is part of a cooperative project between the Bureau of Mines and the Air Materiel Command. The Zr-Cr system was one of the first investigated because of the possibilities of improving the properties at elevated temperatures, the chemical corrosion resistance, and the mechanical properties of zirconium in a manner similar to the enhancement of the properties of titanium by additions of chromium. There is no published work on the Zr-Cr system but from the similarity of the metals involved it was expected that it would be similar to the Zr-Fe' and Ti-Cr' systems. The materials used in this investigation were prepared in the Bureau of Mines laboratory at Albany, Ore. Zirconium was produced by magnesium reduction of zirconium tetrachloride, and a typical analysis is as follows: Fe, 0.06 pct; Ox, 0.08; N?, 0.01; C, 0.02; and other impurities such as Al, Pb, Ni, Ti, and Si less than 0.01 pct each. High purity chromium was prepared by treating crushed electrolytic chromium in a stream of dried and purified hydrogen." The resulting powder contained about 0.01 pct 0 and about 0.1 pct total metallic impurities. All alloys were prepared by arc-melting 50 g briquetted compacts of the desired composition in a Kroll-type" arc furnace using an inert atmosphere. The furnace was evacuated twice and backfilled with helium, which was gettered by melting a center zirconium button immediately before the alloys were melted. Alloys were remelted at least once to insure greater uniformity of composition and subsequently were annealed in vacuum at 1250°C for 48 hr. Fairly homogeneous alloys were obtained by this means; a slight loss of chromium from the surface by evaporation during the high temperature homogenization was noted. All alloys were analyzed for chromium and gave results in good agreement with the nominal composition. Spot checks on tungsten and nitrogen showed pick-up of these elements to be negligible. Over 70 alloys were prepared for use in this investigation; only the critical ones are shown in Table I. Alloys containing up to 10 pct Cr were amenable to hot working at 850°C and a number of these were sheath rolled to 1/16 in. thickness. Specimens were cut from the sheet for use as metallographic samples. For the thermal analysis a differential couple was used in conjunction with an X-Y recorder, the temperature of the specimen and the difference in ternperature between it and the standard nickel body were recorded simultaneously. Heating and cooling rates of 5°C per min were used. The sensitivity of the instrument was such that a difference in temperature between the specimen and standard equivalent to 0.1 mv produced a deflection of 1 in. on the recording chart. The chromel-alumel thermocouples were checked against a Bureau of Standards calibrated thermocouple. Melting-point determinations were made in a high vacuum induction furnace using an optical pyrometer. The pyrometer, calibrated against nickel, copper, and zirconium (iodide process) under near black body conditions, was focused on the base of a hole drilled in cylindrical samples. A North American Philips Geiger counter X-ray spectrometer was used for all diffraction studies. This instrument, in addition to supplying precise intensity measurements of planar reflections, has an added advantage in that metallographic specimens mounted in bakelite can be used directly, and this

Jan 1, 1953

By N. J. Grant, D. S. Bloom

N recent reports, Sully' and Beck and coworkers' I have advanced hypotheses concerning the formation of the phase. Both of these hypotheses are based on Pauling's theories of the electronic configuration of the elements of the first transition group. Sully considered that the number of electrons which can be absorbed in filling electron "holes" is the factor which determines whether or not the structure can form. Beck suggested that the presence of a certain concentration of electron "holes" is the controlling value. It can be shown that a similar criterion can be developed without making reference to Pauling's theories. Table I shows the elements of the first transition group and the incidence of the a structure in the binary systems of these elements according to the data presently available. Also appended is the number of electrons considered to exist in the 3d-4s levels of these elements. If the atomic percentages for the phase are listed as shown in Table 11, and if the number of electrons in the 3d-4s levels per atom is calculated for the a boundary values, the results are as shown in the last column. It can be seen that the numerical values are all in the vicinity of 7 electrons per atom. This is true also for the ternary Cr-Mo-Ni IT phase, which occurs in a system in which none of the binary compositions are known to develop the phase. In the Fe-Mo binary, the high temperature a phase, which occurs at a composition of 50 atomic pct of each element, also yields a ,;1 e of 7 electrons per atom. From inspection of Tables I and 11, it develops that any series of sequential numbers which is assigned to the elements under consideration will result in the numbers pertaining to a compositions grouping themselves around one specific number. It does not follow, however, that this random number necessarily has physical significance. Such a point has already been discussed by Hume-Rothery." One interesting point develops from this study, however, and that is the position of manganese with reference to the other elements and to the phase. In the system used here, the formation of phase is associated approximately with the value of 7 electrons per atom, which is also the number of electrons per atom that manganese has. Manganese, it will be recalled, exists in three different crystal forms, none of which are the usual, simpler metallic forms; on the other hand, elements just to the left of manganese (in Table I) generally have lower coordination-number structures (body-centered cubic) than do elements to the right of manganese (face-centered cubic). The contribution to a complex crystal structure by the interalloying of elements from opposite sides of manganese is significant in that the a phase is formed in binary systems including one element from each side of manganese, with manganese capable of participating with both sides. It is indeed an interesting coincidence that manganese, with 7 electrons per atom, solidifies in complex crystal forms, and that when alloys of the transition elements are made which have seven 3d-4s electrons per atom, they, too, tend to assume a complex crystal form. From the above, it might be deduced that the study of the a phase might be advanced by a critical examination of the element manganese and how its structure is affected by small additions of elements which change the 3d-4s electrons per atom number. The role of atom size would also be of interest in formation. References ' A. H. Sully: The Sigma Phase in Binary Alloys of the Transition Elements. Journal Inst. Metals (1951) 80, Part 4, p. 173. 2 S. Rideout, W. D. Manly, E. L. Kamen, B. S. Lement, and P. A. Beck: Intermediate Phases in Ternary Alloy Systems of Transition Elements. Trans. AIME (1951) 191, p. 872; Journal of Metals (October 1951). "W. Hume-Rothery, H. M. Irving, and R. J. P. Williams: The Valencies of the Transition Elements in the Metallic State. Proc. Royal Soc. (September 1951) 208A. p. 431.

Jan 1, 1954

By Alan Kissock

MOLYBDENUM is thought of as one of the rarer elements, for though it occurs in almost every country of the world it is seldom found in commercial quantities. In this country, however, there is one deposit which makes the term "rare" a misnomer. There are two commercially mined molybdenum minerals: molybdenite, the sulfide, and wulfenite, a lead molybdate. Of these two only the former is of any con- sequence but wulfenite is of mineralogical interest. It is frequently associated with oxidized lead ores and particularly in arid sections. Deposits, however, are usually quite superficial. It is highly oxidized and yet it does not appear to be an alteration product for it apparently disappears below water level and I know of no case where primary molybdenite, or in fact any molybdenum whatever has been identified below these surface wulfenite occurrences. The genesis of wulfenite would make an !- interesting study.

Jan 1, 1933

THE 143d* meeting of the American Institute of Mining and Metallurgical Engineers was held in New York, Feb. 19-22, 1934. It consisted of the annual business meeting, 45 technical sessions at which 217 papers were presented (more than ever before), two sessions of the Board of Directors, two meetings of Section delegates, three formal lectures, luncheon Monday, Tuesday and Wednesday for members and guests, three group dinners and five group luncheons, eight committee meetings, the annual reception and dinner dance, an informal dance, a smoke-dinner and the annual meeting of the Woman's Auxiliary. Attendance showed an improvement over the previous year, as follows: Total, 1534 in 1934, and 1475 in 1933; dinner dance, 543 and 426; smoker-dinner, 425 and 394; informal dance, 295 and 250; women's registration, 160 and 133; luncheons, 1034 and 734. The Coal Division held a general session and three sessions on Coal classification. It also met jointly with the Committee on Ground Movement and Subsidence. At the general session, John B. Dilworth presented a report of the Committtee on Methods of Valuing Coal Proper- ties and R. H. Sweetser a report of the Committee on Evaluation of Coal for Blast-furnace Coke. C. B Huntress, Executive Secretary of the National Coal Association, was the principal speaker at a luncheon on Monday, at which Eli T. Conner, Chairman of the Division, presided H. N. Eavenson, newly elected President of the Institute, and Edward W Parker, Secretary-Treasurer, of the Anthracite Institute, also spoke. The Executive Committee of the Division met Tuesday afternoon. The Sectional Committee on Classification of Coal met on Thursday morning and the Technical Committees on Scientific and Use Classification of Coal on Thursday afternoon. The Committee on Mining Methods held two general sessions, one for presentation of a half-dozen interesting papers on strictly mining subjects, the other on Aerial Transportation. It also participated jointly in a session on ground movement and subsidence with the committee of that name and the Coal Division The Institute's Standing Committee on Aviation had its inception at the session on Aerial Transportation

Jan 1, 1935

By C. S. Roberts

The creep mechanism and kinetics of fine-grained magnesium have been studied over the temperature range 200&apos; to 600°F. As a result of a photographic study of microstructural changes, transient and steady-state creep components have been correlated with slip, subgrain formation, and cyclic deformation at the grain boundaries. THE approach of this research has been the blend of a quantitative study of the creep strain of polycrystalline magnesium as a function of time, stress, and temperature with direct microstructural observations of the operative deformation processes. The validity of the conclusions is dependent on the condition that the microstructural changes seen on the polished surface qualitatively represent those occurring in the bulk of the metal. The work was intended as much to lay a background to a study of highly creep-resistant magnesium alloys as to provide a description of the behavior of the base metal itself. The spectroscopic analysis of the electrolytic magnesium used in this study is as follows: Al, 0.009 pct; Ca, <0.01; Cu, 0.0011; Fe, 0.021; Mn, 0.012; Ni, 0.0004; Pb, 0.0012; Si, <0.001; Sn, <0.001; and Zn, <0.01. The impurity level is approximately that of commercial magnesium alloys. The original ingot was melted under Dow type 310 flux and cast as a 3 in. diam billet. It was extruded into 1 in. flat stock under the conditions: billet preheat 800°F (1 hr), container and die temperature 800°F, speed 3 ft per min, and area reduction ratio 45:1. The extrusion process was chosen in preference to rolling and recrystallization because it allowed easier grain size control from specimen to specimen. The grains of the extruded metal were fairly equi-axial and uniform in the size range of 4 to 6 thousandths of an inch. The preferred orientation of basal planes about the transverse direction was determined by an X-ray diffraction surface reflection method. A beam of filtered copper radiation was directed at an angle of 17" to both the transverse direction and the surface yet perpendicular to the extrusion axis. Analysis of the (002) diffraction arcs in the resulting photographic patterns gave an approximate intensity distribution along the great circle which extends through the center of the basal plane pole figure and to the extrusion axis poles. Successive layers of metal were removed by macro-etching between exposures. The extruded texture is relatively sharp, but the most significant point is the position of the maximum basal plane pole density and its variation with depth below the surface. Fig. 1 shows that this maximum is rotated 15" from the normal at the surface toward the extrusion direction. Such an inclination has been reported for extruded 1 pct Mn and 8 pct A1-0.5 pct Zn alloys.&apos; The inclination decreases until the maximum splits at about 0.025 in. depth into two elements of equal and opposite rotations from the ideal. The double texture persists to as great a depth as was experimentally convenient to examine. It probably continues to the very center of the extrusion. There is no great change in the sharpness of the individual elements of the texture with depth. A plate of metal about 0.015 in. thick at the surface of the extruded stock was produced by etching. A transmission diffraction pattern was made for the purpose of determining any preferred orientation of a direction in the basal planes. Relatively uniform {loo) and {101) rings were produced. There is little tendency for parallelism of a given direction in the plane with the projection of the extrusion axis on it. The creep specimens were machined from 6¼ in. lengths of the extruded stock. Creep was measured on the reduced section, ½x1/8X2¼ in. long. This section was electropolished on one side for the studies of microstructural changes during creep. An orthophosphoric acid-ethyl alcohol electrolyte was used under the conditions recommended by Jacquet.² Hand polishing was used for previous mechanical preparation. Electropolishing was continued until all mechanical twins had been removed. The electro-polished surface was protected from oxidation during creep testing by a thin layer of silicone oil. All micrographs were taken at room temperature on conventional metallographic equipment and after removal of the oil film. The creep tests were performed with machines which have been described in detail by Moore and McDonald." Five testing temperatures, 200°, 300°, 400°, 500°, and 600° ±3°F were used. Difference in temperature between the two ends of the specimen reduced section was 2°F or less. The testing was done at constant load. Strain readings were taken as frequently as necessary to develop usable creep curves. Tensile Creep vs Time, Stress, and Temperature A definition of terms is necessary. Whenever successive sections of a creep strain-time curve show decreasing, constant, and increasing slope with time they will be termed primary, secondary, and tertiary

Jan 1, 1954

By R. D. Pehlke, J. V. Gluck, R. L. Louvet

A study has been made of the effect of small additions of bismuth on the activity of zinc in dilute solution in molten tin. Free-energy interactions have previously been determined between zinc and various third elements where the solvents were molten bismuth or molten lead.&apos;-4 In both of these solvents, the activity of zinc exhibits a strong positive deviation from ideal behavior (at 550°C y° for zinc in lead is 11.4 and for zinc in bismuth is 3.0). The present work, using tin as the solvent, is an extension to a case where the positive deviation is considerably diminished (y°Zn at 550°C is 1.63). Several previous investigators have studied the Zn-Sn binary system; however, little data is available in the range below 0.1 mole fraction zinc.5= Previous high-temperature galvanic cell studies in the Sn-Zn-Bi ternary system included the determination by Gluck and Pehlke of interactions in the bismuth-rich corner1 and separate investigations of the central region by Oleari and Fioriani6 and by Ptak and Moser.7 Yokokowa et al.8 conducted Knudsen effusion studies in the central region; however, their experiments at 625°K were conducted somewhat below the present experimental temperature range. Their results indicated an increase in zinc activity with the addition of bismuth. The present series of experiments was conducted in galvanic cells represented as follows: Zn Zn++ in LiCI-KC1 eutectic Zn + Bi in Sn (pure reference (fused salt electrolyte) (molten alloy) standard) The experimental apparatus. a multi-electrode system employing alumina crucibles and contained in a Vycor tube under a helium atmosphere, has been described previously, as have been the experimental procedures, precautions, and the methods of data reduction.1-4,- The experimental measurements were made over the range from 450° to 650°C. Between thirty and forty measurements were made in each run. The linearity of the electromotive force vs temperature relations was verified by linear regression techniques. The correlation coefficients exceeded 0.99. The experimental results summarized in Table I include the interpolated electromotive force at 550°C and the temperature dependence of electromotive force. Only results from stable and consistent cells containing more than 0.025 mole fraction zinc are reported. Attempts to run cells at 0.01 or 0.02 mole fraction zinc were not satisfactory. This is attributed to the closeness of the free energies of formation of the chlorides of tin and zinc. Calculations employing Wagner and Werner&apos;s criteria for displacement reactions10 indicated that reduction of the zinc content to 0.01 mole fraction places the cell near the borderline concentration for a 1 pct error in measured potential. The compositions shown in Table I are the actual weighed-in amounts. Previous experience has indicated that compositional changes during the running of a stable cell are negligible.&apos; Over the range of compositions studied for the binary alloys, the activity coefficient of zinc was essentially constant indicating that Henry&apos;s law is followed to 0.05 mole fraction zinc. The temperature, OK, de-

Jan 1, 1969

By A. U. Seybolt

The solubility limit of oxygen in columbium has been determined in the range between 775&apos; and 1100°C by means of lattice parameter measurements and microscopic examination. The solubility is a function of temperature and varies, in the range given above, from 0.25 to 1.0 pct O, respectively. BECAUSE of the marked deleterious effect of oxygen upon the mechanical properties of some of the transition metals, it is desirable to know something about the solubility of oxygen in these metals. The brittleness caused by oxygen in solution is particularly marked in the case of the group VA elements, vanadium, columbium, and tantalum. The solubility of oxygen in vanadium has already been reported in an earlier paper,&apos; and Wasilewski2 has given a value (0.9 wt pct) for the solid solubility of oxygen in tantalum at 1050°C. Brauer3 in 1941 investigated the Cb-0 system up to Cb2O5, but made no real effort to investigate the extent of oxygen solubility in the metal. He made the observation, however, that this solubility must be less than 4.76 atom pct (0.86 wt pct) oxygen. This estimate was made from X-ray diffraction results on the alloys CbO, CbO, and CbO; all alloys consisted of the terminal (Cb) solid solution plus CbO, but the last alloy containing 4.76 atom pct 0 showed only three very weak CbO lines. It is surprising that Brauer, by examining only three alloys, arrived at an estimate of the solubility which agrees very well with the results to be reported herein. Experimental Procedure A columbium strip obtained from Fansteel Metallurgical Products was cut into strips, 0.020x1/2x2 in. Two holes, about 3/16 in. in diameter, were made near the ends of the strips in order to hold them against a flat steel block for mounting in a General Electric X-ray spectrometer for lattice parameter measurements. The same holes were used to hang the specimens inside a fused silica vacuum furnace tube which was part of a Sieverts&apos; gas absorption apparatus. The apparatus and method of adding oxygen gas has been previously described.1 According to the supplier, the columbium obtained had the analysis given in Table I. After degreasing the samples, approximately 0.001 in. was etched from each side of the samples in order to remove possible surface impurities from the last rolling operation. For this purpose the following cold acid pickle was found satisfactory: 8 parts HNO3, 2 parts H2O2 and 1 part HF. Various Cb-O compositions were obtained up to 0.75 wt pct O by the gas absorption and diffusion technique. After the sample had absorbed all the oxygen gas added at 1000°C, an additional 24 hr was allowed for homogenization. This treatment appeared to be adequate, as shown by the linearity of the lattice parameter-composition plot. More concentrated alloys were prepared by arc melting mixtures of Cb and Cb2O5 since it was very time-consuming to make Cb-0 alloys in the neighborhood of 1 pct O, or over, by the diffusion method. When the flat strip specimens were used, they were ready for the X-ray spectrometer after cooling from the Sieverts&apos; apparatus. The cooling rate obtained by merely allowing the hot fused silica furnace tube to radiate to the atmosphere (when the furnace was lowered) was sufficiently fast to keep the dissolved oxygen in solution. Arc-melted alloys were reduced to —200 mesh powder in a diamond mortar, wrapped in tantalum foil, sealed off in evacuated fused silica tubes, and then heat treated as indicated in Table 11. The fused silica tubes were quickly immersed in cold water without breaking the tubes after the heat treatments. The tantalum foil prevented reaction between the fused silica and the sample; there was no reaction between the powdered samples and the foil at 1000°C, but some trouble was experienced at 1100°C. At this temperature level a reaction between the sample and the foil was sometimes observed, which resulted in erroneous parameter values. Experimental Results Hardness Tests: Since most of the X-ray samples were in the form of flat strip, it was convenient to obtain Vickers hardness numbers as a function of oxygen content. Compared to the V-O case,&apos; oxygen hardens columbium much more slowly, presumably because of the larger octahedral volume in colum-bium (about 12.0 compared to 9.3Å3 in vanadium), hence, requiring less lattice strain for solution. The plot of VHN vs wt pct O is shown in Fig. 1.

Jan 1, 1955

By D. W. Lillie

It has been demonstrated that considerable bend ductility exists in bulk specimens of polycrystalline high-purity silicon. The possibility of hot-forming at 1200°C is suggested. EXCELLENT corrosion resistance in many media and low cross section for absorption of thermal neutrons (0.13 barn) would make silicon of interest to nuclear engineers were it not for extreme brittle-ness and the difficulty of fabrication by any reasonable means. The use of silicon for structural purposes also has been considered in view of its light weight and oxidation resistance. Johnson and Han-sen&apos; have investigated the properties of silicon-base alloys and concluded that there was no way of making pure silicon or silicon-rich alloys ductile at room temperature. In view of reports of appreciable ductility in germanium single crystals above 550°C&apos;." and some plastic deformation in single-crystal silicon above 900oC,&apos; the present investigation was undertaken to define more precisely the limits of high-temperature ductility in pure silicon. After this investigation was begun torsion ductility in both germanium and silicon was reported by Greiner." Through the courtesy of F. H. Horn, a small bar of cast extra high-purity silicon was obtained and small bend specimens were made from it by careful machining and grinding. All of the reported tests results were obtained from samples from this bar (bar No. 1) and one other of similar source (bar No. 2). No complete analysis was obtained but, based on analysis of similar semi-conductor grade material, metallic impurities were under 0.01 pct total. Vacuum-fusion analysis for oxygen showed a value of 0.0018 2 0.0003 pct for the first bar tested and metallographic analysis showed no evidence of a second phase. Bend tests were carried out on an Instron tensile machine using a bend fixture with a 1 -in. span loaded at the center. Supporting and loading bars were 0.250 in. round and the load was applied by downward motion of the pulling crosshead of the machine. Specimen thickness and width were approximately 0.10 in. and % in. respectively. Loading rate was controlled by holding crosshead motion constant at 0.02 ipm. In some cases a smaller specimen was used on a 5/8-in. span with a 0.129-in.-diam loading bar. The entire bend fixture was surrounded by a hinged furnace and all heating was done in air atmosphere. Temperature measurement was made with thermocouples fastened directly to the bend fixture within less than 1 in. from the specimen. Autographic stress-strain curves were recorded during each test, and breaking load, total deflection, and plastic strain could be obtained from these curves. Stress was calculated from the beam formula S = 3PL/2bh2, where P is the load in pounds, L the span in inches, b the specimen width in inches, and h the specimen thickness in inches. This formula is strictly correct only in the elastic range but has been used to calculate a nominal stress for convenience in the plastic range. The stress given is the maximum stress in the specimen. Results The results of the complete series of tests are shown in Table I. The first group of tests (specimens Nos. 1-6) showed the beginning of plastic flow at a test temperature of 900°C, so two additional tests (Nos. 8 and 9) were made at 950°C on small-size specimens from bar No. 2. Specimen No. 8 was tested in the as-machined condition, and No. 9 was heat-treated in hydrogen at 1300°C for 2 hr, cooled to 1200°C and held 1 hr, cooled to 1000°C and held 1 hr, cooled to 900°C and held 1 hr, and finally cooled to a low temperature before removal from the hydrogen. It is apparent that the heat-treatment had a significant effect on yield strength and ductility. In addition, the magnitude of the yield point was conslderably reduced in the heat-treated specimen as is shown m Fig. 1 by tracings of the stress-strain curves. After obtaining a furnace capable of reaching higher temperatures specimens Nos. 10 to 13 were tested at 1100 and 1200°C. Strain rate was increased by up to a factor of 10 to see whether the ductility observed was excessively strain sensitive. Specimen NO. 10, strained at 0.02 ipm and 1100oC, was still bending at a deflection of 0.322 in. when the load rate was increased to 0.2 ipm, resulting in immediate

Jan 1, 1959

By Beall, John V.

THIS is not simply the story of how a water filled shaft was developed into a million-ton- a-year producing mine in the space of four critical years, although it is reason enough for telling it, but it is also the saga of an engineering achievement in which knowledge nurtured by years of experience in coal and ore mines was blended together and the best from each type of mining selected. The entire system of mining was detailed on maps by the mining engineering department before the shaft was unwatered, and subsequent development followed these plans nearly to perfection. The selection of machinery was particularly critical as it was necessary to push production from only a few headings in the early stages of development and metal mine machinery was being used in a coal panel-system of mining. At the start of World War I1 the demand for iron ore to supply Woodward blast furnaces, and rapid exhaustion of the main source of Wood- ward ore, No. 3 Red Ore mine, necessitated speedy opening of the Pyne mine. The mine is three miles southwest of Bessemer and is responsible for 80 pct of Woodward ore, the rest coming from the Songo mine. The Woodward Iron Co. is one of the old producers of the Birmingham district. S. H. Woodward, an iron-master of Wheeling, overheard two Union soldiers conversing about ore and coal lands in Alabama, which lead to the acquisition of the first ore lands of the Woodward Co. in 1869. Development was not begun until after the death of S. H. Woodward; his two sons, W. H. Woodward and J. H. Woodward, formed the Woodward Iron Co. in 1881 and purchased a tract of land midway between the ore vein on the southeast and the coal field on the northeast about 12 miles southeast of Birmingham for the

Jan 1, 1950

By M. G. F. Sohnlein

IN a Bolivian tin concentrator an appliance was needed to furnish a suitable product for fine jigging from a pulp of the following composition: Mesh Per Cent. +20 8.0 +40 36.5 +60 9.0 +80 10.5 +100 5.5 +150 4.51 -150 25.0 99.0 Loss 1.0 IN the jigging process, particles of cassiterite as small as 0.1 mm. can be recovered, provided they are not present in excess, that is if the material treated on the jigs contains sufficient coarser sands to keep the interstices between the grains open. Removing the fine material from the pulp by screening, to prepare the jig feed, is impractical, because that means the use of an 80-mesh screen or finer, and is not as effective as hydraulic classification. A screen would eliminate mineral grains from the feed which can be recovered by jigging, and in addition would throw more gangue and low-grade middling on to the jig. Formerly a one-spigot Richards vortex classifier had been used to accomplish this separation, but the tangential openings through which the hydraulic water enters became clogged by fine vegetal matter with which the water was contaminated, and which it was impossible to remove from the water. Consequently the work of the classifier was imperfect and a good deal of slime was sent to the jig. When designing the plant referred to in this paper it was decided to use a hydraulic classifier as shown in Fig. 1. The essential features had been copied from the Anaconda classifier.1 This remodeled classifier consists of a truncated pyramidal wooden hooper A with an attachment of cast iron

Jan 4, 1916

By M. G. F. Söhnlein

In a Bolivian tin concentrator an appliance was needed to furnish a suitable product for fine jigging from a pulp of the following composition: Mesh Per Cent. + 20 8.0 40 36.5 + 60 9.0 + 80 10.5 + loo 5.5 4-150 1 4.5 -150 25.0 99.0 Loss 1.0 In the jigging process, particles of cassiterite as small as 0.1 mm. can be recovered, provided they are not present in excess, that is if the material treated on the jigs contains sufficient coarser sands to keep the interstices between the grains open. Removing the fine material from the pulp by screening, to prepare the jig feed, is impractical, because that means the use of an 80-mesh screen or finer, and is not as effective as hydraulic classification. A screen would eliminate mineral grains from the feed which can be recovered by jigging, and in addition would throw more gangue and low-grade middling on to the jig. Formerly a one-spigot Richards vortex classifier had been used to accomplish this separation, but the tangential openings through which the hydraulic water enters became clogged by fine vegetal matter with which the water was contaminated, and which it was impossible to remove from the water. Consequently the work of the classifier was imperfect and a good deal of slime was sent to the jig. When designing the plant referred to in this paper it was decided to use a hydraulic classifier as shown in Fig. 1. The essential features had been copied from the Anaconda classifier.&apos; This remodeled classifier consists of a truncated pyramidal wooden hopper A with an attachment of cast iron

Jan 1, 1917

By FRANK RIEBERS

IN DISCUSSING the selection of a geophysical method, much of what the writer will say is applicable to any of the various methods and to their use in prospecting, whether for oil or for other minerals. Specifically, the writer&apos;s subject is the problem, particularly pressing on the Pacific Coast, of checking the rising cost of the discovery of new fields by the proper employment of geophysical methods. Table I was prepared from statistics published by the California State Milling Bureau. The writer selected five of the largest a:ld most active companies operating in California, segregated the number of wild-

Jan 1, 1930

By Charles R. Simcoe

The stress-strain curves in the microyield region for various Fe-C solid solutions shown by Davies and Ku are typical examples of parabolic curves defined by the expression a = kEn 111 These data, when replotted on log-log coordinates, as shown in Fig. 9, exhibit three essentially parallel straight lines. It is apparent that carbon increases the flow stresses, but does not affect the exponent n. In other words, the only factor in Eq. [1] affected by in in carbon content is the constant k. As Eq. [1] is written k is the stress at a strain of 1.0. This is unsatisfactory for examining data in the microyield region. Therefore, the equation can be altered to the form: to permit the use of the authors&apos; microyield stress at a strain of 10-6 as k. Extrapolating the curves in Fig. 9 to a strain of 10-6 gives stress values of 2000, 3200, and 5400 psi for 0.008, 0.014, and 0.02 pct C, respectively. These values do not agree exactly with the authors&apos; measured values, but this will not affect the following discussion. The effect of carbon content on the slopes of the stress-strain curves shown in Fig. 2 of the paper by Davies and Ku can be analyzed by differentiating Eq. [2] with respect to strain. Thus: where n is always less than 1.0. Since n is essen- tially constant as a function of carbon content for the data under discussion, the slopes of the stress-strain curves depend only on k and E. If the slopes are examined at various selected Plastic strains. i.e., 10-6, 10-5, and so forth, it follows from Eq. [3] that the dif-ferent slopes for the different carbon contents depend only on the different values of ke=10-6. Thus, the larger ke=10-6, the steeper the linear stress-strain curve will rise with increasing plastic strain. This

Jan 1, 1969

Jan 1, 1908

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

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

Jan 1, 1965

By d&apos, K. Mukherjee, C. R. Antonio, R. J. Maciag, G. J. Fischer

Tensile data indicate that over the range of strain rates 10-5 to 10-1 sec-1 and in the temperature range 298° to 743°K the flow stress at a given temperature may be expressed as: C0 = Cem where m changes abruptly at a critical strain rate of 10-2 sec-1. The Zener-Hollomon parameter was tested and found to be invalid except at temperatures exceeding 700° K. Values of AH calculated for temperatures above 700°K ranged from 30 to 47.5 kcal per g-mole. ThE flow characteristics of aluminum and aluminum alloys as a function of temperature and strain rate have been of interest to various experimenters for many years. Trozera et al.1 determined tensile flow curves for pure aluminum and concluded that the combined effect of temperature and strain rate on the flow stress could be related using the Zener-Hollomon parameter. More recently, Hockett2 proposed a relationship between compressive flow stress, temperature, and true strain rate which could be represented by a surface. Holt et al.3 studied strain rate effects on flow stress in a number of aluminum alloys at room temperature. It was determined that there is a critical strain rate above which a strain rate effect is observed. It was also reported that the strain rate sensitivity was significant in aluminum alloys in the "0" condition only. In a recent review paper McQueen4 has considered a number of mathematical expressions which have been used to describe the relationship between stress, strain rate, and temperature. These expressions have been applied to the flow characteristics of a number of different metals and alloys including aluminum. In the present work the strain rate sensitivity of 7075-0 aluminum was determined in the temperature range of 298° to 743°K. The tensile flow stress at 0.2 pct offset was obtained over a nominal strain rate range of 10-5 to 10-1 sec-1. EXPERIMENTAL Threaded tensile specimens were cut from a single heat of 7075-T6 aluminum. The composition of this heat is given in Table I. The test bars had a gage section 1.5 in. long by 0.250 in. diam and conformed to ASTM specification E-8-57T. After machining, the bars were annealed at 413° ± 10°C for 2 hr. They were then cooled to 260°C in 3 hr, and finally air cooled to room temperature. This treatment is commonly used to produce the "0" condition. Load-time curves at constant crosshead speeds were obtained at various temperatures using an Instron testing machine. Crosshead speeds ranged from 0.002 to 40 in. per min. A three-zone resistance tube furnace was used for the elevated-temperature tests. Temperatures were measured at three points along the gage length by means of suitably placed thermocouples. Each tensile bar was held at temperature for 30 min prior to testing and the maximum temperature variation along the gage length was kept below 1°C. In all, 275 samples were tested and each data point plotted is an average of at least two tests. In many cases the point represents up to six tests. RESULTS AND DISCUSSION Values of the flow stress at 0.2 pct offset at six different temperatures are plotted vs strain rate on log-log coordinates in Fig. 1. Over discrete ranges of strain rate, the data for each temperature fit the expression:

Jan 1, 1969

By Gene D. Clayton, Robert R. Dimock

A time-consuming and expensive preshearing program to minimize the adverse effects of blasting on slope stability at Kennecott Copper Corp.&apos;s Ruth Pit in east-central Nevada has been eliminated in favor of down-the-hole, nonelectric delayed blasting which can produce a smooth wall effect and improve blast fragmentation. The new blasting approach resulted from a Kennecott engineering investigation aimed at improving the stability of the extremely variable rock conditions found throughout the pit by reducing the vibrational energy imparted to the walls with conventional bench blasts.

Jan 4, 1977

By E. P. Fleming

COMPARED to the situation abroad, the domestic industry continues to lag both as regards the production and consumption of newly mined lead. During 1938 we produced and consumed slightly over 20 per cent of the world output, whereas ten years ago the figure was nearly double this pro- portion. Labor difficulties and absence of demand were chiefly responsible for the general inactivity. In the foreign field, in spite of low metal prices, production and consumption of lead equaled or exceeded all previous records. Practically all the large companies, with the exception of those in Spain, increased operations, though it should be noted that the foreign lead mines have higher-grade ores than domestic mines. In view of the rapid expansion of the foreign industry, it is natural to expect greater progress abroad, particularly in process metallurgy.

Jan 1, 1939

By Ralph Hultgren, David W. Mitchell

Magnesium alloys usually are superheated before casting in order to ensure fineness of grain. Superheat temperatures in common use range from 1600" to r 7o0°F.; the casting temperature, which depends upon the mold shape, is usually 200° to 300°F. lower. The process of superhcating requires considerable time and seriously shortens the life of the iron pots used. Recently it has been reported1 that if acetylene, carbon dioxide or natural gas is bubbled through molten electrolytic A.S.T.M. No. 4 alloy at 1400°F. for 5 min., grain refinement equivalent to that of superheating will take place. Addition of certain solids such as graphite or aluminum carbide accomplishes the same results? As will be shown in this paper, it is possible to achieve grain refinement in magnesium casting alloys at low temperatures by mechanical stirring of the molten metal for a short time. This process was developed in the course of research work, supervised by the War Metallurgy Committee under the "Restricted&apos; project NRC-550, for the Office of Production Research and Development of the War Production Board. This paper, based on that work, has been released for publication by the O.P.R.D. Materials and Methods The alloys studied were the most common American sand-casting alloys designated as No. 4 and No. 17 by the American Society for Testing Materials. The magnesiun used in these alloys was of both carbothermic3 and electrolytic&apos; origin. Chemical analyses supplied by the producers are shown in Table I. Each heat consisted of approximately 5 lb. of alloy melted in a Tercod crucible. It was refined by fluxing with Permanente No. 7* refining flux at 1300° to 1350°F. After cooling to 1200° to 1250°F., portions of approximately one pound each, were ladled into iron crucibles contained in an electric furnace at about 1250°F. The molten metal was covered with Permanente No. 21 † covering flux and then heated to the temperature to be investigated. Normally each of the four portions was given a different treatment. In a typical case one portion was stirred vigorously for 5 min., acetylene gas was passed through a second portion for 5 min., a third portion was superheated to 1600°F. for 15 min., then . cooled to casting temperature, and the fourth was held for 5 min. at the temperature of stirring or gassing without other treatment. Each portion was then cast into one-inch diameter cylinders in three "nonturbulent" molds of identical shape. One mold was made of cast iron and the other two of baked sand. The cast-iron mold and one of the baked sand molds were heated to 360°F., the other baked sand mold was at room temperature. The freezing times in these molds were

Jan 1, 1945