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By S. Suphi Yavasca, A. M. Gaudin

THIS paper is intended as a contribution to our knowledge of the mechanism of comminution and of the work of crushing. In a previous paper' it was shown that with quartz comminution proceeds as follows I. The size distribution of broken fragments made by a single fracture is such that the new surface on each grade is the same. 2. Multiple fracturing results in a size distribution such that in the fine sizes the surface per grade is the same in every grade; in coarse sizes the surface per grade decreases gradually with increasing size. In that paper it was mentioned that determinations on minerals other than quartz were in course of completion in order to establish the generality of these observations. In this paper, condensed data2 are presented for galena, pyrite and glass. Galena and pyrite are crystalline material and glass is noncrystalline. Galena has excellent cubic cleavage. Pyrite, although cubical, does not have marked cleavage. Quartz, on which the original determinations were made, does not cleave and although crystalline (hexagonal) breaks conchoidally. Glass breaks much like quartz. It is apparent, therefore, that the minerals selected represent some range in character of the solid without covering all possible types. GLASS Fifteen glass marbles were crushed individually in the pendulum crusher described in the preceding paper,1 then subjected to careful screening for 30 min. Six sized fractions were selected and cleaned in a hot 0.12 N solution of hydrochloric acid, washed with distilled water and dried on a hot plate. This was followed by an examination with a binocular microscope, to remove foreign matters not eliminated in cleaning as well as to eliminate "compacts" of fine particles. These compacts are groups of fine iragments that seem to be mechanically stuck together as a result of localized compacting during the comminution operation. The presence and the abundance of these compacts may be related to the amount and direction of the forces applied in different crushing devices. Since, properly, such compacts should be entirely eliminated in the sizing analyses, it is necessary to remove them to the last before making surface determinations on sized fractions. For example, with a - 28 + 35-mesh glass the surface areas of two samples, one cleaned with acid and under the binocular, the other only washed, were 102 and 172 sq. cm. per gram, respectively. Examination of the samples under an Ultropak microscope showed that washing alone failed to remove the compacts and also that it fails to remove certain fine dusts attached to the particles. Cleaning with acid loosens the fine dusts and

Jan 1, 1945

By A. S. Joy

Vacuum flotation tests carried out according to the method of Schuhmann and Prakash1 have shown that the acid limiting edge of the flotation area for a Brazilian hematite, in the presence of dodecylamine, is a straight line of slope approximately unity. The flotation tests and the structure, surface ionization, and electrokinetic properties of this hematite have been fully discussed elsewhere. 2 The numbers of adsorbed H+, and OH- ions and collector molecules have been determined in the range of critical conditions defining the acid limit of the flotation area. The total amine adsorption is shown in Fig. 1 as a set of contours superimposed on the straight part of the flotation area. These were determined by spectro-photometric estimation of the complex formed between residual amine and the anionic dye Orange II.3 The ionic strength of the solutions was kept constant and at a value in sufficient excess of the amine concentration to ensure that the diffuse part of the double layer was populated predominantly by indifferent ions. Adsorption of H+ and OH- in the absence of amine was found by potentiometric acid-base titration in the presence of hematite.4 The form of the adsorption-titration curves suggested that the hematite surface behaves in an amphoteric manner, and that positively charged sites arise through loss of a hydroxyl ion, and negatively charged sites by loss of a hydrogen ion. On this basis, curves 8 and 9, shown in Fig. 2, were calculated from the titration curves. These show the variation of the numbers of positive (s +) and negative (s—) sites with pH. To distinguish between ionic and other modes of adsorption, zeta-potential determinations have also been made using the streaming potential technique. The influence of amine on the zeta-potential of the mineral over a wide pH range is shown in Fig. 3. The change in charge ?s, due to adsorption of amine ions in the Stern layer, was calculated by applying the Gouy-Chapman theory, as modified by Stem, to the results shown in Fig. 3. The validity of this treatment has been shown by Ottewill and Jaycock.5 The three full lines, Nos. (1) through (3), included in Fig. 2 show the relationship between ?s and pH at three amine concentrations. The general conclusion from the zeta-potential curves is that adsorption of amine causes a reduction in the negative charge on the surface. Comparison of the values shown in curves (1) through (3) of Fig. 2 with the - curve shows that the magnitude of the reduction is comparable with that of s - at any given

Jan 1, 1964

L. S. PANYITY.-I made inquiries from the Smith and Dunn people, who are the originators of the compressed air and gas method of increasing the production of oil wells, as to how much pressure the sand will stand; that is, relative to the original rock pressure. They tell me that they have not been able to show, up to date, any pressure in a sand greater than the original pressure. I have also made 'a statement to that effect, but I am really dubious as to whether that is right, as I am not sure that you cannot get a greater pressure. However, I think that a greater pressure would be dangerous because it might cause a loss of gas. C. H. SHAW, ? Lawton, Okla.-In regard to the gas that was put into the pool up in New York State, may it not be possible that, on account of errors, etc., in measuring or computing, there is a mistake in the apparent fact that more gas was gotten out than was put in? L. S. PANYITY.-Unfortunately, I have not the papers I expected from those people to show the actual conditions, but I do not doubt that such

Jan 4, 1919

By R. D. Daniels, T. G. Oakwood

A study was made of the effects of small quantities of hydrogen on the mechanical properties of colum-bium. Tensile specimens, hydrogenated to concentrations of 20 to 200 ppm, were tested at temperatures of 300°, 191°, and 77°K. Although hydrogen was found to have little effect on the strength of columbium, the ductility of Cb-H alloys was found to be quite sensitive to both hydrogen concentration and temperature. At 300°K, an abrupt loss in ductility occurred at a critical hydrogen concentration, although some ductility was observed beyond the tolerance limit. A similar result was found at a lower hydrogen concentration at 191°K. At 77°K, however, a more gradual loss in ductility with increasing hydrogen concentration was observed. Hydrogenated columbium was thus observed to undergo a ductile-brittle-ductile transition. Metallographic examination of fractured specimens revealed extensive porosity at both 77° and300°K which was a distinct function of hydrogen content. At 191°K, although some secondary cracking was noted, the amount of observed porosity was minimal. These observations are interpreted in terms of hydrogen solubility and mobility as a function of temperature and in the role of hydrogen in promoting growth of microcracks. lHE effect of hydrogen on the mechanical properties of the refractory metals is not, at present, completely understood. A number of studies have shown these materials to be susceptible to hydrogen embrittlement. Roberts and Rogers1 have found that vanadium can be embrittled by hydrogen. It was further demonstrated that fracture undergoes a ductile-brittle-ductile transition as the temperature is lowered from 150° to -196°C; i.e., there is a ductility minimum observed at a certain temperature. The ductility is increased by either raising or lowering the temperature from this point. A more complete study by Eustice and Carlson2 on vanadium containing 10 to 800 ppm placed the ductility minimum at about -100°C with variations reportedly due to hydrogen content and strain rate. Ductility minima have also been found at certain temperatures for tantalum containing 7 ppm H3 and 140 ppm H.4 At hydrogen concentrations above 270 ppm, however, the ductility return at low temperatures was considerably reduced.4 In the case of columbium, some disagreement exists in the literature. Eustice and Carlson,5 Wilcox et al.,6 and Imgram et al.4 failed to find a ductility minimum although a composition-dependent ductile-brittle transition was observed. Hydrogen concentrations in these investigations were 20 ppm,5 1 to 30 ppm,6 and 200 to 390 ppm.4 However, Wood and Daniels7 observed a rather pronounced ductility minimum at hydrogen contents ranging from 19 to 252 ppm. Those theories of hydrogen embrittlement involving the precipitation of diatomic hydrogen which have been applies to ferrous metals8-12 do not seem to be applicable to the case of columbium and other exothermic occluders. Such theories propose that extensive crack formation and propagation occurs by the precipitation and expansion of diatomic hydrogen at internal voids and microcracks. However, photomicrographs of hydrogenated columbium do not show any evidence of damage introduced by the sorption and precipitation of diatomic hydrogen; rather, at high hydrogen concentrations, a hydrogen-rich second phase is precipitated.13'14 In addition, a number of these theories require the development of high hydrogen pressures at voids in the structure.8'10'12 This does not appear to be feasible in the concentration ranges discussed in the aforementioned paragraphs. The possible interaction of atomic hydrogen with microcracks resulting from dislocation pile-ups15,16 remains in doubt since pile-ups have not been observed in bcc metals17 including columbium.18 Wood and Daniels7 have put forth the possibility that a hydride precipitation could be responsible for crack nucleation in columbium. Work by Longson19 has shown that hydrogen embrittlement of columbium parallels the bulk solubility limit; i.e., as the solubility increases, for instance with temperature, the amount of hydrogen necessary to cause embrittlement also increases. Although a hydride precipitation appears attractive as a means of nucleating microcracks in columbium, what require more intensive study are the low-temperature anomalies which have been observed, i.e., the ductile-brittle-d'ictile transition characteristics. Also, the hydrogen concentrations where embrittlement occurs are often below the bulk solubility limits determined by Albrecht et al.13,14 and Walter and Chandler.20 This work is an attempt to determine more definitively the effects of concentration and temperature on the mechanical properties of dilute Cb-H alloys. EXPERIMENTAL PROCEDURE Ultrahigh-purity columbium rods, obtained from the Wah Chang Corp., were cold-reduced by rotary swaging. A chemical analysis is given in Table I. The material was cut into cylindrical blanks 1.50 ±0.005 in. long. Individual specimens were either given a stress relief anneal at 750°C or recrystal-lized at 1200°C. Resulting microstructures were either a "bamboo" structure characteristic of a wrought material or a recrystallized structure with a grain diameter of approximately 100 n. All heat treatments were carried out in a vacuum of 10-5 Torr or less.

Jan 1, 1969

By Thomas J. Sawarynski

This paper discusses current trends of coarse and fine coal refuse disposal techniques. Emphasis is on site-specific engineering used by coal companies to tailor safe, cost effective, and environmentally sound refuse disposal system to the needs of a particular mine. Geotechnical design considerations will be discussed in relation to system performance, regulatory acceptance, and industry use.

Jan 1, 1982

Executive DEGOLYER, Chairman SIDNEY H BALL RICHARD PETERS, JR WILLIAM H BASSETT J V W REYNDERS Finance GEORGE D BARRON, Chairman H A GUESS GEORGE OTIS SMITH Membership J M CALLOW, Chiarman FRANK L ESTEP WILBER JUDSON GEORGE D BARRON H N SPICER Alternates P A MOSMAN EDWARD B STURGIS

Jan 1, 1923

By Nathaniel Herz

The use of zinc dust for precipitating the pecious metals from cyanide solutions is well established now in many places, and has many advantages over the shavings method of precipitation. Although much work has been done o,n methods of testing zinc dust, as yet. no absolutely positive test has been devised to determine the value of the material. Certain facts are known, but often it happens that results on a working scale are not as expected from the laboratory tests. The purpose of this paper is to record some obscrvations made while testing a large variety of zinc-dust samples in the laboratory. W. J. Sharwoodl has described standard analytical methods, which have been followed, with the changes noted. The regular determinations include zinc oxide, by solution in ammonia and ammonium chloride, lead, and precipitating efficiency. In some cases cadmium was determined by a method similar to that described by J E Clennell.2 I will discuss the precipitating-efficiency test in detail. The procedure is as follows: "A solution of potassium silver cyanide is prepared by dissolving 10 grams of silver cyanide (AgCN) and 5 grams of 99 %' potassium cyanide in a little water and diluting up to 1000 cc. It is then adjusted by addition of a little more XCN or AgCN until the solution indicates from 0.12% to 0.15% free KCN by titration with standard silver nitrate. The titration is best made by using a 10-cc. or 20-cc. sample, adding 1 CC. of 2 % potassium iodide, and a slight excess of ammonia, as the end point is then sharper. Or 15 grams of pure crystallized XAg(CN)2 may be dissolved in a liter of water and 1.5 grams XCN added. " Weigh out 0.5 gram zinc dust into a 300-cc. beaker. Add a few cubic centimeters of watcr and stir until zinc is well mixed, then pour in 250 cc. of the prepared solution, stirring vigorously. See that all lumps are broken up, and continue stirring for fully five minutes. Stir occasionally (at least every 10 minutes) until the end of two hours from the addition of the solution. Then filter upon an 11-cm. filter, wash precipitate thoroughly, sprinkle with test lead, wrap it carefully in the paper, place in a scarifier with about 20 grams test lead, burn paper cautiously in muffle, scorify five minutes, cupel at low temperature and weigh silver. Milligrams silver obtained from 0.5 gram zinc X 0.0606 = percentage precipitating efflciency."³

Jan 1, 1916

By J. F. Abel, F. T. Lee

Subsidence is controlled by a complex com¬bination of mining and geologic factors. For example, a compilation of worldwide data shows that, as the percentage of shale in the overlying rock mass decreases and the amount of sandstone increases, the angle of draw (and the area affected by subsidence) decreases. Limestone in the over¬burden appears to cause a more than twofold decrease in the angle of draw compared to a like amount of sandstone. Increased amounts of sandstone were accompanied by a greater surface subsidence relative to the mining height. The total thickness of overburden did not appear to influence the subsidence magnitude above super-critical panels. The greater the thickness extracted, the smaller percentage of that thickness shows up at the surface as subsidence. The greater the percent of the seam extracted, the greater the subsidence reaching the surface. The maximum subsidence above room-and-pillar panels de¬pends on the pillar height and minimum width as well as the other factors listed.

Jan 1, 1984

By George M. Schwartz

WHEN reviewing the progress made in mining geology for the year 1953, one might say that not much has been accomplished and, indeed, in a subject such as economic geology not much progress should be expected in the 10 months of the year which elapsed before this article was prepared. This seeming lack of progress, however, disappears when the facts are investigated a bit. There undoubtedly are more economic geologists at work than ever before. It is probably not an exaggeration to say that more geologists are now employed by a single company in the Lake Superior district than were employed in the whole district 20 years ago. In most mining districts geologists are busy with numerous problems of production, development, and exploration and some give an occasional thought to the scientific problems of the science, or rather the art, of mining geology. In fact, this very intense activity of mining geologists is one reason why progress seems slow; they do not have time to write up results of investigations. There is also a great amount of work being done which is not released because of company policy. Conditions have improved very much in recent years but mining corporations, in general, have some distance to go before attaining par with the petroleum industry in this respect.

Jan 2, 1954

Hunkered up against the spine of the Andes in a tight valley where natural refuge from avalanche hardly exists is the daring Rio Blanco project of Cerro Corp. The deposit here was found in 1904, but nature has foiled all previous attempts to open it. To an experienced mountaineer or a highway engineer with mountain experience, the avalanche hazard in the valley of the Blanco river would be immediately apparent. The collar shaft is at the head of the valley at an elevation of 3600 m and for 12 km down the valley there is no space on the floor for building very much; the dissected rock walls are roadways for avalanches and even a highway could not be maintained sufficiently passable. This is the proposition taken on by the Cerro Corp. Chilean National Decree #1699, passed on December 9, 1966, signified "Go" to the Compania Minera Andina, a company whose shares are held 70% by the Cerro Corp. and 30% by the government of Chile. The orebody, although only partially delineated, contains proven reserves of 120 million tons of ore averaging 1.58% Cu. When the operation comes on stream in the last quarter of 1970, it will be at the rate of 11,000 tpd. Annual production will be 65,000 tpy of recoverable copper in concentrates.

Jan 11, 1969

P. Herasymenko (New York University, New York) —The authors' experiments on equilibria between water vapor and liquid synthetic slags represent a valuable contribution to our knowledge of the nature of liquid slags. They can be regarded as a proof of ionic splitting of water molecules dissolved in slags. The assumption that water dissolved in slag was com- pletely ionized was made in my report on hydrogen equilibria in steelmaking as early as 194010. In that paper, the first systematic data were given on the content of ionized hydrogen in acid and basic open-hearth slags. The paper probably escaped the notice of the authors, although they mention the articles published later by other investigators who reported erratic and

Jan 1, 1958

By W. C. Phalen

INTRODUCTION NOBODY will dispute the fact that the conservation in every legitimate manner of our valuable high-grade phosphate-rock deposits is a present-day problem of importance. The table and curve, given herewith, show. that during the past 10 years the exportation of high-grade rock has averaged very close to half the total output of the entire country. The bulk of this exportation is from Florida, for obvious reasons. It is plain that the deposits in this State, more particularly, are being wastefully depleted under a system of selecting the cream of the product for exportation to Europe, leaving the comparatively low-grade rock, running from 65 to 70 per cent., and under, in bone phosphate of lime, for our own n fertilizer manufacturers to work up when all the best rock is gone. In this paper the writer has endeavored to make a point of describing in some detail the important methods of production and conservation in Tennessee. These ought to prove of educational value to our American agriculturists and fertilizer manufacturers, and should result in a demand for the highest-grade rock, both for direct application to the soil and for use in making acid phosphate. It is certainly evident that the European

Jan 10, 1916

By Robert L. Akright

LOCATION AND HISTORY The Candelaria silver mine is located in an arid, isolated desert setting in Sections 3 and 4, T.3N., R.35E., and Section 33, T.4N., R.35E., Mineral County, Nevada (Fig. 1). Silver was discovered in 1863 by Mexican explorers, and high grade silver veins were mined from the early 1870s through the 1880s. Essentially all mining had ended by 1890. The veins were mined by underground methods typical of the period. As is the case in many mining districts, Candelaria was studied and explored by a number of companies. All these efforts were terminated short of mine development because of low silver prices and difficult metallurgy. On March 1, 1976, Occidental Minerals (Oxymin) entered into a Limited Partnership agreement, known as Candelaria Partners, as General Partner with Congdon and Carey Ltd. No. 4. Prior to the agreement, Congdon and Carey had acquired the candelaria properties as part of a bullish silver program and did considerable exploration which indicated the possibility of a large reserve of shallow silver mineralization. GEOLOGY AND ORE DEPOSITS Silver and gold mineralization in the Candelaria district occurs in high-grade fissure veins with silver values ranging from 0.6 to 7.8 kg/t (20 to 250 oz per st). These veins, combined with the low grade disseminated mineralization in the intervening material between the veins, form Manto- like deposits 15 to 46 m (50 to 150 ft) thick. Three such deposits are found in the Candelaria district: the Lucky Hill, Mount Diablo, and Northern Belle deposits (Figs. 2 and 3). The average ore grade of the Lucky Hill and Mount Diablo [ ]

Jan 1, 1985

By C. F. Wang

Page I. Introduction............:.............. 395 Manchuria in General ....................... 395 Pen-hsi-hu............................ 397 Pen-hsi-hu Coal & Iron Co., Ltd................... 399 I1. organization........................... 400 III. Coal Deposit........................... 402 Location..............................402 Geology............................. 403 Coal Mining...........'.................. 404 Mining Methods........................407 Mining Cost.........................408 IV. Coal Washing Plant.......................408 V. Coking Plant..........................410 VI. Iron Deposit...........................413 Magnetite Belt.......................... 413 Origin of Deposit......................... 414 Iron Mining........................... 415 VII. Concentration Plant........................ 417 VIII. Briquetting Plant.......................... 418 IX. Blast-furnace Smelting...................... 418 iNTKODtrCTION Manchuria in General Manchuria. called the "Three Eastern Provinces" in Chinese. forms the northeastern corner of China and is bordered by Siberia on the north and northeast. and by Korea on the east. It is a land famous in Chinese annals as the place of origin of the Ching dynasty. and in more recent times it has bcen an arena for diplomatic maneuvering and commercial competition between the Russians. advancing from the north. and the Japanese from the southeast. It derives its name of "three eastern provinces" from the fact that it is divided into three provinces; Hei-

Jan 1, 1918

By C. Pin, J. Bruce Wagner

In order to demonstrate the role of defect chemistry in the solid state to a process-metallurgy reaction, laboratory experiments were carried aut to remove copper from liquid lead using lead sulfide which had been doped to provide definite concentrations of cation vacancies. The removal of copper decreases in the order: bismuth- or antimony-doped PbS, undoped PbS or tin-doped PbS, and silver-doped PbS. The data are explained using the simple mass -action law and in terms of the exceedingly rapid interstitial diffusion of coppw in PbS to vacant cation sites. Results are in agree-ment with thermodynamic predictions and certain industrial practices that copper may be removed from lead below the limit of its coexistence with pure Cu,S and pure PbS. The role of defects in solids has been exploited in semiconductors and many device applications, in explaining tarnish formation, dissolution rates, and mechanical properties. The application of these principles to many process-metallurgical problems has not received as much attention. It was the purpose of this study to illustrate the role of defect structures of solids in a process-metallurgical application. When lead is refined, the ore, galena (PbS), is reduced by a series of operations to liquid lead (lead bullion) containing impurities such as copper, bismuth, antimony, arsenic, and silver depending on the original composition, the fluxes added, and the particular type of operation, see Fig. 1. In order to produce a pure lead, a series of refining operations are carried out. A typical lead-bullion analysis before drossing is shown in Table I. Copper is removed first as its presence increases the zinc consumption during the desilverizing process. For preliminary copper removal the lead bullion is brought to a temperature of 440°C in a kettle of 60 metric tons capacity. Some tar (or sawdust or resins) is usually added and the kettle is cooled slowly to 400°C while the liquid is stirred. A solid phase, called a dross, floats on top of the liquid and the particles of the solid phase adhere to the tar. This "hot dross" is collected. It contains mostly lead and copper which are partly oxidized and/or sulfurized if the lead bullion contains some sulfur.*

Jan 1, 1963

By C. R. Masson, M. L. Pearce

The nitrogen contents of seven specimens of iron and steel were determined by the three methods. Good agreement won generally observed between the results of the isotope -dilution and Kjeldahl determinations, tltzts establishing the reliability of the isotope -dilutzon technique. For some specimens, the vacuum-fusion values at 1650 °C were lower than the corresponding Kjeldahl values by up to 0.0015 pct absolute. These differences were eliminated for a specimen of "pure" iron by performing the vacuum-fusion analyses at 2100 ° to 2240 °C. The reason for this relatively high temperature required m the vaczium-fusion analyses is discussed. ThE determination of nitrogen in iron and steel has been the subject of numerous investigations and a concise review of the extensive literature in this field has recently appeared.' Two methods of analysis are most commonly employed, the vacuum -fusion and the chemical or Kjeldahl method. Except in special cases where the presence of certain alloying elements may present difficulties, both methods are generally regarded as applicable, although the vacuum-fusion method is more sensitive and is often preferred for samples of very low-nitrogen content. The method of isotope dilution, first employed for the determination of gases in metals by Kirshenbaum and Grosse,2 has recently been applied to the determination of nitrogen in iron and steel.3,4 The method is attractive in that it does not require the quantitative extraction of gas from the metal specimen. Staley and Svec3 modified the standard Kjeldahlpro-cedure by introducing, along with the steel sample, a measured amount of ammonium sulfate enriched in the isotope 15N. The nitrogen content was obtained by measuring the isotopic ratio 15N/14N in the resultant solution. The technique involved the distillation of nitrogen as ammonia from alkaline solution and subsequent oxidation of NH4+ in the distillate to gaseous nitrogen. The results for iron and steel samples of commercial origin were often in reasonable agreement with values quoted by the suppliers, although occasional marked discrepancies were observed, particularly with the results of vacuum-fusion analyses. Preliminary work in this laboratory4 on the determination of nitrogen by isotope-dilution in the gas phase yielded results for three samples which were significantly higher than the values obtained by vacuum-fusion. The present paper describes an extension of this work to a wider variety of samples. Analytical results by the Kjeldahl method are also reported. EXPERIMENTAL The technique employed for the isotope-dilution determinations was similar to that described elsewhere.4 Several minor modifications were made to the apparatus. These included the use of molybdenum instead of platinum-rhodium suspending wires when crucibles were degassed at temperatures above 1600°C. The circulatory system used previously for converting CO to CO2 was replaced by a single chamber, the walls of which were cooled directly in liquid nitrogen. Temperatures were measured with an optical pyrometer which had been recently calibrated and, as in the previous study, were minimum values obtained by sighting on the center bottom of the crucible. Temperatures obtained by sighting on the interior walls were always higher by 100' to 130°C with the design of crucible employed. Flat-bottomed crucibles exhibited an even larger temperature difference. To check the efficiency with which crucibles were degassed in the isotope-dilution apparatus, several experiments were done in the vacuum-fusion apparatus, suitably modified4 for isotope-dilution studies. Faster pumping speeds and higher degassing temperatures were possible, the latter due to the use of a generator with a higher power output (10 Kva at 398 kc per sec). In these experiments the combustion of CO was omitted and a correction4 was made for the contribution of CO to the ion current at m/e 28, used in determining the isotopic ratio R = l5NP4N. This correction did not seriously influence the re-

Jan 1, 1962

J. R. Lane (Metals Research Laboratory, Washington)—A new type of deformation called "kinking" has recently been described. Is there any relation between the "rumpling" described in this paper and "kinking?" D. C. Jillson (author's reply)—Both are manifestations of bending about [210] axis. The difference is one of degree. W. C. Ellis (Bell Telephone Laboratories, New York) —Some observations of deformation in zinc recorded in this paper may be applicable generally to flow in metals. One of these, deformation in torsion without evidence of slip or twinning in the early stages and with startling ease, when the twist is about the hexagonal axis, adds another method of flow to the presently increasing list of mechanisms. This illustrates again that a crystal will utilize any realizable process to flow and relieve stress. The process is not necessarily classical directional slip—& this case, it is rotational slip. The question naturally occurs: Will face-centered cubic metas stressed by twisting about an octahedral axis flow in a similar manner by rotation on an octahedral plane? I would like to ask Dr. Jillson if he has made any experiments or knows of any experiments of this type on face-centered cubic metals? Face-centered cubic metals possibly would behave differently from zinc, since, for one thing, the stacking sequence is different for the two structures. The results of such experiments, however, would be instructive in providing more information about deformation processes. D. C. Jillson—Dr. Roy E. Swift, working in the Hammond Laboratory at Yale, performed a twist test on a single crystal of brass. The work has not been published, and I do not know the crystallographic direction of the axis of the specimen used. Lo-ching Chang (Columbia University, New York)— Observations similar to Figs. 1 and 2 of the paper were obtained by us during the bending and unbending of an orthorhombic Au-Cd alloy.'l This orthorhombic alloy is the product of diffusionless transformation from a single crystal of p Au-Cd alloy (CsC1 structure) containing 47.5 atomic pct Cd on cooling to about 60 "C.62 Referring to the effects of annealing, has the author tried any loilg time high temperature anneal, such as 150 to 200 hr at 40O°C? D. C. Jillson—No. C. Crussard (Ecole des Mines, Paris: France)—I

Jan 1, 1952

By Howard Martens, Pol Duwez

IN two papers published in 1949, alloys of chromium with the refractory metals tungsten, molybdenum, tantalum, and columbium were investigated in view of their possible use as high temperature resisting materials. For the Cr-Ta system, a partial phase diagram was presented and the only intermediate phase was identified at Ta2Cr3. A phase of the same composition was also observed in the Cb-Cr system. The X-ray diffraction data presented in these papers, however, were insufficient for crystal structure determination. It is shown in the present study that the only intermediate phase in both the Ta-Cr and the Cb-Cr systems corresponds to the ideal stoichiometric ratio TaCr2, or CbCr2. Both structures are cubic, MgCu, type. At high temperature, however, TaCr2 has a hexagonal MgZn, type structure, which can be retained at room temperature by fast cooling. The alloys were prepared by melting in a helium arc furnace on a water-cooled plate. The design of the furnace was essentially the same as that described in ref. 3. Some alloys were also obtained by sintering compacts made of the mixed powders pressed at 80,000 psi. The sintering was carried on for 4 hr at 1375°C. The tantalum and columbium powders were supplied by Fansteel Metallurgical Corp., North Chicago, 111. The tantalum powder was the reagent grade, with a particle size smaller than 400 mesh and a total impurity content less than 0.1 pct. The columbium powder was smaller than 325 mesh and contained approximately 0.1 pct C and traces of Fe, Ti, and Zr. The electrolytic chromium powder from Charles Hardy, Inc., New York, was smaller than 300 mesh and contained about 0.1 pct Na, 0.05 pct Ca, and traces of Cu, Al, Mg, Si, and Co. Powder diffraction patterns were obtained with a 14.32 cm camera, using copper Ka radiation filtered through nickel foil. The powder pattern of the TaCr2 alloy obtained by sintering at 1375'C was different from that obtained on the same alloy rapidly cooled from the melt. Contrary to this result, the powder pattern of CbCr2 was the same, whether the alloy was made by sintering at 1375°C or by melting, and was similar to that of the TaCr, sintered. It was also found that the structure of the TaCr2 specimen obtained by melting was retained after heating for 4 hr at 1590°C, but transformed into the structure found in the sintered specimen after heating for 4 hr at 1375°C. Hence, the structural change of TaCr2, appears to be a reversible polymorphic transformation. CbCr2 and ToCr2 Structure, Low Temperature Form By using large scale Hull-Davey charts, the powder pattern of CbCr, and of the low temperature form of TaCr2 were readily interpreted on the basis of a face-centered cubic lattice with a parameter of approximately 6.95 kX. The indices of the reflections together with the values of sin' 0 are given in Tables I and 11. From this list of observed reflections, it appears that the (200), (600), (024), (046), and (028) reflections are missing. The lack of (h00) reflections for h 4n indicates a four-fold screw axis. The missing (Okl) spectra for k + 1 An indicate the existence of a diamond glide d. The combination of these symmetry elements can be found in the O— Fd3m space group, which is therefore the most probable one. After having determined the approximate density of TaCr, by the immersion method, the number of molecules per unit cell was calculated and found to be nearly eight. This information, added to the fact that the most probable space group is O leads to the consideration of a structure of the MgCu2 type, in which the atoms have the following positions: 8 magnesium in a and 16 copper in d. On the basis of this structure, intensities were computed by means of the usual formula: 1 cos'20 I a sin2 cos where F is the structure factor; 8, the Bragg angle: and p, the multiplicity factor. As shown in Tables I

Jan 1, 1953

By Henry S. Rawdon

The structure of wrought iron as usually described by metallographists and workers in metal in general is that of a fairly pure iron. Impurities, if present, are usually considered as being in solid solution in the crystals of the ferrite matrix or as forming part of the ever present "slag streaks." Attention is herein directed to one type of these dissolved impurities; to the detection of such impurities, particularly in low-grade irons, and to their possible influence on the physical properties of the metal. The attention of the Bureau of Standards was first directed to wrought iron of the peculiar and unusual characteristics to be described later, in material which had failed in service and was submitted for test. The examination was extended to other grades of wrought iron, to see whether such features are of common occurrence in this class of material. MICROSTRUCTURE OF WROUGHT IRON Usual Structure The general microstructure of wrought iron is so well known that a detailed description of it here is needless. There is shown in Fig. 2 the structure of a sample of Swedish iron which illustrates well the matrix of ferrite crystals in which are embedded the slag threads so characteristic of the puddling process and the subsequent working of the material. The usual commercial product contains varying amounts of the impurities commonly associated with iron and steel, i,e,, manganese, phosphorus, silicon, and sulphur together with small amounts of carbon. Of these, the larger part of the phosphorus and some of the silicon present are held in solid solution in the ferrite while most of the remaining impurities, other than carbon, exist in the in closures of slag. Aside from the discontinuities introduced by the slag streaks the ferrite matrix has the microstructure and appearance of a pure metal. No definite orientation of the various crystals or grains is apparent; deep etching of the specimens reveals no intracrystalline features (i.e., within the grains) other than those noted in " pure " metals in general (etching pits).

Jan 1, 1918

By A. S. Nowick, E. S. Machlin

ONE of the main criteria used to rate the heat-resisting properties of alloys is stress rupture.1 During a stress-rupture test a tensile specimen is held under a constant load at a constant temperature until it fractures. The chief measurement made during this test is the time required for rupture at the specific test stress and temperature. It was found empirically from a series of stress-rupture tests at a constant temperature that when the logarithm of the time for rupture is plotted against the logarithm of stress a straight line is obtained within experimental error.2~3 This method of showing stress-rupture data has been adopted by many investigators and the KACA.4 By interpolation and extrapolation from these plots, values of the stresses required to rupture the specimens (the rupture strengths) in 10, 100, and 1000 hr are obtained for specific temperatures. Alloys are then rated for a particular application on the basis of their rupture strengths at the rupture life that most nearly represents the application. Inasmuch as stress rupture is an important criterion in rating heat-resisting alloys, it would be advantageous to know the quantitative dependence of the time for rupture on stress, temperature, com- position, and structure. In order to obtain this information, an investigation was made at the KACA Cleveland laboratory during the spring of 1945. The theory of rate processes was used because it has been found to apply to certain processes such as chemical reactions, viscous flow, and creep that occur at a definite rate for given conditions. It was thought that stress rupture was such a process. An equation was derived that gives, for a given com- position and structure, the dependence of the time for rupture on stress and temperature. The investigation is part of a general program to provide information that will lead ultimately to the development of better alloys in order that the efficiency and power output of gas turbines used in aircraft propulsion can be increased. THEORY The theory of rate processes will first be discussed as a general theory. It will then be shown that if stress rupture of heat-resisting alloys can be treated as a rate process, certain equations must be satisfied. Later sections will then show that these equations are satisfied. General Theory of Rate Processes The theory of rate processes5 eveloped by Eyring and others has been applied to chemical reactions as well as to other processes such as viscosity of liquids and diffusion. In every case in which rate- process theory can be applied, there is a small subdivision, so that the macroscopic process is the net effect of all the small processes. This smallest subdivision is called the "unit process.'' For example, in a chemical reaction the unit process is

Jan 1, 1947