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By Thomas Leonard Watson

Introduction,...... Historical Statement,....644 Geology of the District,....645 The Weisner Quartzite,....647 Topography,. .....653 Rock-Weathering,..... The OcheR-Deposits,.....655 Petrography of the Quartzite,..655 Associated Ore-Deposits,....657 Chemical Composition of the Ocher,. 658 Mode of Occurrence of the Ocher,..659 In the Fresh Rock,....660 In the Residual Clays,...661 Origin of the Ocher,....662 Economic Features,..... Methods of Mining,..... Preparation of the Ocher,...664 Uses,........ Introduction. Knowledge of the existence of yellow-ocher deposits in Bartow county, Georgia, dates back to the early mining of manganese- and iron-ores in the vicinity of Cartersville. Systematic mining of the ocher in this area really began, however, probably not longer than a decade back, although the date of its first working is as early as the year 1877. The district has been, for a number of years, one of the principal producers of yellow ocher in the United States; and at no period of its development have mining activities been greater and more successful than at present. Systematic field-study of the ocher- and manganese-deposits of Georgia was begun by me while I was a member of the

Jan 1, 1904

By Frederic Becket

IN a recent article,1 which described the softening effect of columbium in plain high-chromium steels, the authors stated that their investi-gations had shown columbium to be also a particularly valuable inhibitor of intergranular corrosion in steels of the 18 per cent chromium, 8 per cent nickel type. It is the purpose of the present paper to record some of the results obtained through the introduction of columbium to the austenitic chromium-nickel steels. The damaging effects of this type of corrosion have become so widely known as to restrict considerably the applications of the steels under consideration, and therefore there is little question of the importance of the goal to be attained. Numerous contributions concerning the susceptibility of the aus-tenitic chromium-nickel steels to intergranular corrosion have appeared during the past few years, and among others who have dealt construc-tively with the subject are such well-known authors as Strauss and Houdremont of Germany, Hatfield of England, and Bain in the United States. Different theories have been propounded as to the cause of intergranular corrosion, and various remedial measures have been proposed, the majority of which involve the use of addition agents. Titanium is the addition agent at present most generally employed, as suggested by Houdremont and modified as described by Bain, Aborn and Rutherford.2 Little has been published on the effects of holding these steels for long periods at the relatively lower temperatures in the presence of

Jan 1, 1934

By Claude H. P. Lupis, John F. Elliott

The classic Siez~erts' technique has been employed to determine the solubility of oxygen in liquid pure silver and the effect on the oxygen solubility of solute metal additions to liquid silver. The results indicate that oxygen deviates slightly from Sieverts' law in pure silver as = 3.9. Gold, platinum, md palladium decrease the solubility of oxygen in silver. First-order free energy, enthalpy, md entropy interaction coefficients are determined from the data. An important aspect in the establishment of the formalisms to be applied to represent the thermody-namic behavior of components of solutions is the accuracy of the experimentally determined thermody-namic properties. Wagner developed the first-order free energy interaction coefficient.' Recent papers2'3 extend the treatment formally to other thermodynamic properties and define the second- and higher-order interaction coefficients. A current communication4 considers in some depth the requirements and limitations imposed because of experimental error on the use of several formalisms now under active consideration in the field. This communication reports the results of an experimental study of the behavior of oxygen in liquid silver alloys that was carried out concurrently with the development of Refs. 2 and 3 with the hope of providing sufficiently precise information so that enthalpy and entropy interaction coefficients could be determined. THE EXPERIMENTS The Sieverts technique was employed using an improved design of the reaction bulb over that developed originally by Humbert5 and subsequently improved by pehlke6 and Weinstein.7 The Vycor reaction bulb as shown in Fig. 1 was air-cooled and contained a port for the thermocouple angling off to one side and a vertical port for connections to the gas supply and

Jan 1, 1969

By J. J. Gilvarry

Recently, Gilvarry1,2 has given a rigorous derivation of the proper distribution function for fragment size in single fracture, based on a closely defined physical model and deduced strictly by the laws of probability. The physical point of departure is Griffith's theory of brittle strength, identifying sub-microscopic flaws as the cause of the low strength of a solid in comparison with values implied by cohesive energies. Gilvarry and Bergstrom,4-7 and Gilvarry8 have compared the predictions of the theory with experiment, and have found excellent agreement, in general. The purpose of this communication is to sketch the extension of the theory to the case of comminution, and to indicate the applications to some examples in nature. The present treatment represents an amplification of a brief discussion appearing elsewhere. 9 Although the basic ideas of the Griffith theory are perfectly general for rupture of brittle solids, it was originally formulated with very brittle materials such as glass in mind. Moreover, Griffith's original experimental work was carried out on glass specimens. Recently, however, the theory has been extended by race" to apply directly to rocks. This extension makes the theory immediately applicable to the materials generally of interest from the standpoint of comminution. GENERAL CASE To obtain the distribution function for fragment size in single fracture, three assumptions are made, that: 1) Fracture proceeds by activation of preex-istent Griffith flaws in the volume, faces, and edges of a fragment; 2) the distributions of flaws of these three types are independent of each other; and 3) activated flaws of a particular type are distributed at random, individually and collectively, in the sense of Fry.11 The last assumption implies that each distribution is separately of Poisson type.

Jan 1, 1964

By W. H. Furlonge

WHILE fulfilling professional engagements, my travels over this portion of the Transvaal have been quite extensive—always on horseback however, so that anything like a thorough investigation of the ground passed over has been necessarily impossible; still, the more minute examination of certain small areas, coupled with general observations, has enabled me to form some idea as to the prominent geological features of the country as a whole. Anything like a complete or comprehensive description is indeed out of the question, as there are no proper maps of the country and the facilities for observation are limited. A large plateau, called the "High Veldt," stretches from east to west across the Transvaal. It is generally level, or gently rolling, and has an average elevation of 6000 feet above the sea; it is destitute of timber, and in fact greatly resembles the western prairies of North America. Rock-outcrops are not common in it. It terminates very abruptly to the east and northeast, the descent of 2000 or 3000 feet into the mountainous country that occupies its borders being made in a

Jan 1, 1890

By F. N. Rhines, T. E. Leonitis

The oxide scale that forms upon magnesium at elevated temperatures is non-protective in the sense that the rate of oxidation is constant and thus does not decrease with the growth of the scale as it does with other common metals. This generality was first stated by Pilling and Bedworth' and has been verified by Suzuki2 and by ScheiL3 Pilling and Bcdworth argued that the nonprotective characteristic could be predicted from the fact that magnesium oxide occupies less space than does the metal from which it springs, wherefore the scale is not expected to cover the metal so completely as to exclude all direct access to the atmosphere. Linear oxidation is thought by Scheil to be common to all cases where the reaction occurs at the oxide-metal interface. According to Suzuki," he product of high-temperature oxidation in the air is MgO contaminated with no more than traces of a nitride. When the metal is allowed to burn freely a fume composed of cubic crystals of Mg04 is given off. Delavaults observed that excrescences form upon liquid magnesium and alloys in thc course of oxidation. Beyond this it is known that the use of atmospheres containing small quantities of sulphur dioxide6 or carbon dioxide serve to retard the oxidation of solid magnesium and that beryllium' and calciums minimize the oxidation of molten magnesium exposed to the air. Many studies have been devoted to the nature and rates of "protective" oxidation, as exemplified by the cases of copper and iron, wherein the rate is characteristically parabolic. The theory of parabolic oxidation is well developed.~ Linear oxidation, on the other hand, has received but little attention and the theories proposed by Pilling and Bedworth and by Schcil have yet to withstand careful examination. There exists no comprehensive survey of the high-temperature oxidation of magnesium (or of any other metal that exhibits linear oxidation) over a broad range of temperature, under a variety of atmospheric conditions and covering a large group of alloys. It has been the purpose of the present investigation to provide such a survey, with the object of gaining a fuller understanding of linear oxidation, especially as applied to magnesium. Experimental Procedure and Results The experimental studies undertaken were of two kinds: (I) measurement of the rate of oxidation as influenced by the 6c

Jan 1, 1946

By T. E. Leonitis, F. N. Rhines

The oxide scale that forms upon magnesium at elevated temperatures is non-protective in the sense that the rate of oxidation is constant and thus does not decrease with the growth of the scale as it does with other common metals. This generality was first stated by Pilling and Bedworth' and has been verified by Suzuki2 and by ScheiL3 Pilling and Bcdworth argued that the nonprotective characteristic could be predicted from the fact that magnesium oxide occupies less space than does the metal from which it springs, wherefore the scale is not expected to cover the metal so completely as to exclude all direct access to the atmosphere. Linear oxidation is thought by Scheil to be common to all cases where the reaction occurs at the oxide-metal interface. According to Suzuki," he product of high-temperature oxidation in the air is MgO contaminated with no more than traces of a nitride. When the metal is allowed to burn freely a fume composed of cubic crystals of Mg04 is given off. Delavaults observed that excrescences form upon liquid magnesium and alloys in thc course of oxidation. Beyond this it is known that the use of atmospheres containing small quantities of sulphur dioxide6 or carbon dioxide serve to retard the oxidation of solid magnesium and that beryllium' and calciums minimize the oxidation of molten magnesium exposed to the air. Many studies have been devoted to the nature and rates of "protective" oxidation, as exemplified by the cases of copper and iron, wherein the rate is characteristically parabolic. The theory of parabolic oxidation is well developed.~ Linear oxidation, on the other hand, has received but little attention and the theories proposed by Pilling and Bedworth and by Schcil have yet to withstand careful examination. There exists no comprehensive survey of the high-temperature oxidation of magnesium (or of any other metal that exhibits linear oxidation) over a broad range of temperature, under a variety of atmospheric conditions and covering a large group of alloys. It has been the purpose of the present investigation to provide such a survey, with the object of gaining a fuller understanding of linear oxidation, especially as applied to magnesium. Experimental Procedure and Results The experimental studies undertaken were of two kinds: (I) measurement of the rate of oxidation as influenced by the 6c

Jan 1, 1946

By E. C. Tveter, L. A. Roe

The authors present a general outline of the theory and development of heavy-liquid application to mineral processing. Patent literature and processes are reviewed with special emphasis on liquid recovery systems which have been employed or proposed. Advantages and disadvantages of the process are discussed together with the recent developments which have revived interest in this old concentration method. The most important single factor in this resurgence of interest is concluded to be the narrowing gulf between chemical engineering and mineral dressing which has opened the field for new concepts of mineral plant design. A partial summary of patents on heavy liquid separations is included. In spite of the fact that heavy-liquid separation with organic liquids has been used in the laboratory for over 50 years, this process has never graduated to large scale commercial use for any extended period. However, a variation of this process, the sink-float or heavy-media separation process has found wide acceptance and is used to separate minerals from diamonds to gravel. Materials used to increase the specific gravity of the pulps used as heavy media include sand, clay, barite, magnetite, galena, hematite, atomized lead and ferrosilicon. Because of the greater ease of recovery, the magnetic materials, magnetite and ferrosilicon, are the preferred media today. In the U. S. alone, heavy-media iron ore plants with a capacity of over 10 million tons of concentrate per year are in existence. Heavy-media separation involving use of solid, inorganic particles suspended in water rapidly found a wide range of commercial use with the introduction of magnetic media. The minerals engineer is experienced in working with suspensions and quickly learned to develop and control such media at a cost compatible to the type of separation desired. The natural superiority of a heavy liquid with uniform chemical and physical properties has never been questioned since its first use in laboratory mineral separatory procedures. It offers the only method for gravity separation of fine particles of relatively close specific gravity. The most important early attempt to make heavy liquid separations commercial were made by the DuPont Co. which began experimental work on Virginia limonite in 1904. The appended "Partial Summary of Patents" compiled by W.L. O'Connell of The Dow Chemical Co. demonstrates the quantity and sequence of this work. Both inorganic and organic parting liquids were investigated and numerous patents were issued on the use and recovery of these liquids. The work culminated in the heavy liquid plant of the Weston Coal Co. at Shenandoah, Pa. Chemical engineering design of this plant was the responsibility of Francis I. and Hubert I. DuPont. Heavy-liquid separation of coal almost achieved commercial status at this plant which actually processed over 20,000 tons of coal. The liquids used were tetrabromethane, pentachloroethane and trichlo-roethylene, with liquid losses ranging from 8.9 to 12.4 oz per ton of cleaned coal. The reasons for failure of this plant are not clear but probably involved toxicity problems as well as other problems in chemical engineering. Excellent economics were reported. A more recent pilot plant was built in 1954-55 by Norris Goodwin for the Inerto Co. to treat hectorite clay. This plant employed carbon tetrachloride in jigs with liquid recovery by evaporation. Although good separation was achieved, incomplete removal of the CCl, from the clay prevented commercial operation. The only present operations known to the authors employing heavy liquids for gravity separations are limited to the use of calcium chloride in certain coal washers and bromochloromethane in a small batch operation (one ton solids per day) for the separation of beryllium metal particles from slag materials. This is not strictly a minerals beneficiation problem but it has demonstrated the feasibility of such separations. PROBLEMS Critics of early attempts to commercialize heavy-liquid separation of minerals summarize the draw-

Jan 1, 1963

By WILFRED SYKES

IT is with particular pleasure that I welcome the members of the Open-hearth Conference of the I American Institute of Mining and Metallurgical Engineers to this meeting, as I feel this is one of the most useful activities of the Institute in the field of ferrous metallurgy. For the information of our other members I might say the Open-hearth Conference was organized by Mr. Reynders when he was president, and is made up of open-hearth superintendents and metallurgists. All the plants are invited to send representatives, and practically all do, with the exception of the U. S. Steel Corporation. It meets twice a year to discuss various problems in connection with the manufacture of steel, and its minutes are published for the benefit of those attending, the expense being defrayed by the participating companies. This conference, .1 believe, should be a model for activities in the other branches of the work covered by this Institute. It works, not by reading formal papers, which we all know is not a very satisfactory method to bring out the experience of others, but rather by a round-table method of discussion. The spirit of the meetings is such that each member feels perfectly free to state his experience, and he gets as much as he gives. A series of topics for, discussion is brought to the attention of the chairman and after one is exhausted the next point is taken up. In this way there is a real interchange of ideas and experiences which cannot fail l to be of the greatest benefit to those attending. That these meetings are beneficial is evidenced by the "continued growing attendance and lively discussions at these half-yearly meetings.

Jan 1, 1930

By W. H. McFarland

The mechanical properties have been determined for a large number of alloy-free martensitic steels with carbon contents ranging from 0.08 to 0.20 pct and with manganese contents of about 0.4 to 0.5 pet. These steels were tested 1) as water-quenched, 2) after quenching, temper rolling, and tinning, and 3) after tempering treatments which involved temperatures from 400o to 1300oF and times from 1 min to 8 hr. The majority of these tests represent steel from commercial-size coils, i.e., strip 32 in. wide, coil weights up to 20,000 16, and steel thicknesses from 0.0055 to 0.024 in. As a result of these treatments, it has been shown that as-quenched low-carbon alloy-free steels can be produced with tensile strengths ranging from 140,000 to 220,000 psi and tensile elongations from 3.0 to 4.0 pet in 2 in. The tensile strength of the as-quenched martensites can be represented by the equation, tensile strength (ksi) = 119 + 560 (wt pet C). The response to tempering of these steels is related to previous work by Muir, Averbach, and Cohen and by Grange and Baughman. Strain aging of low-carbon martensite has also been investigated. If low-carbon steels are defined as those steels with a maximum carbon content of 0.2 pet, it is found that the literature on low-carbon, alloy-free martensites contains little data on the mechanical properties of these steels. However, the following facts concerning low-carbon alloy-free martensites seem firmly established:'-' 1) The major factors in controlling the strength of the martensite appear to be a) fine structure, b) the internal strain resulting from the transformation, and, particularly, c) the amount of carbon in solid solution. 2) In low-carbon steels, the martensite is auto-tempered and is in the form of needles with only minor amounts of internal twinning, whereas the martensite in high-carbon steels forms as plates which are internally twinned on a fine scale. 3) Care must be taken in comparing the results of work that has been done on low-carbon steels with varying amounts of alloying elements to data on plain carbon steels. As has been noted by Irvine, Pickering, and Garstone,6 alloying elements generally lower the martensite start temperature and, thereby, decrease the amount of auto tempering obtained during the quench. This makes it difficult to

Jan 1, 1965

By W. C. Leslie

The textures of cold-rolled and of annealed iron are compared with those of an iron-0.8 pct copper alloy in which the amount of precipitation after cold rolling was controlled. Previously published pole figures -for cold-rolled and for annealed iron are confirmed. The effects of precipztatiotz after cold rolling are to retain the cold-rolled texture after annealing, to inhibit the formation of the usual allnealing texture, and to produce elongated recrys-tallized ferrite grains. It is suggested that the inhibition of new textures by precipitation after cold rolling is a general phenomenon. A great deal of attention has been paid to the development of texture during the secondary or tertiary recrystallization of ferritic alloys, but very little work seems to have been done on the control of texture during primary recrystallization. If such control were attained, it might be possible to simplify the processing of oriented materials or to change the characteristics of current cold-rolled and an-nealed products. From previous experience, it seemed likely that texture could be controlled by recrystallizing a supersaturated solid solution. Green, Liebmann, and Yoshidal found that the formation of preferred orientation in aluminum (40 deg rotation about <111> relative to the deformed matrix) was inhibited when iron was retained in supersaturated solid solution in the strained aluminum. The authors attributed this inhibition to iron atoms in solid solution. There is, however, an alternative explanation. Green et al, took a highly supersaturated solution of iron in strained aluminum and heated it to an unspecified temperature for recrystallization. It is probable that precipitation occurred prior to and during recrystallization, and it is proposed that the inhibiting agent is this precipitate, rather than the iron atoms in solid solution. It is important to note that precipitation before cold work is ineffective; the effective precipitate is that formed after cold working and either before or during recrystallization. The location and distribution of the precipitate are critical. Precipitation in such a manner has been found to have profound effects upon kinetics of recrystallization and the microstruc-ture of the recrystallized alloys.2-4 It would be surprising, indeed, if this were accomplished with no change in texture. Because of the relative simplicity of the system, and because of previous experience,4-7 it was decided to determine the effect of precipitation on texture in an alloy of iron and copper. Bush and Lindsay5 found an unspecified change in texture in cold-rolled and annealed low-carbon rimmed steel sheets when the copper content exceeded 0.1 pct. MATERIALS In earlier work, the rate of recrystallization of a low-carbon steel was greatly decreased by 0.80 pct copper, and, after the proper treatment, the recrystallized ferrite grains were greatly elongated.4 Accordingly, it was decided to investigate the effect of precipitation on texture at this level of copper content. The iron and the iron-copper alloy were made from high-quality electrolytic iron and OFHC copper, vacuum-melted in MgO crucibles, cast, hot-rolled to 0.2 in., then machined to 0.150 in. The compositions are given in Table I. The plates were heated to 925°C and brine quenched, twice. This produced a ferrite grain size of ASTM 0 in the iron and ASTM 1 in the Fe-Cu alloy. Disk specimens were cut from the heat-treated plates, repeatedly polished and etched, then used to determine (110) and (200) pole figures by reflection. Despite the complication of large grain size, these pole figures strongly indicated a random texture. PROCEDURES The copper content in solid solution in ferrite before cold rolling and recrystallization, and hence, the amount that could precipitate during the recrys-tallization anneal, was controlled at three levels by heat treatment. The specimens as quenched from 925° C were presumed to have all the copper, 0.80 pct, in solid solution. Other samples of the quenched alloy were aged 5 hr at 700°C to retain about 0.5 pct Cu in solid solution.6 A third set of quenched specimens was reheated to 700°C, then slowly cooled in steps, to reduce the amount of copper in solid solution to a very low level. All specimens were cold-rolled 90 pct, from 0.150 to 0.015 in. thick. The rolling was done in one direction only, i.e., the strip was not reversed between passes, with a jig on the table of the mill to keep the short specimens at 90 deg to the rolls. The rolls were 5 in. in diameter and speed was 35 ft. per min. Machine oil was used as a lubricant. In a supersaturated alloy, the maximum effect of the copper precipitate on microstructure and on recrystallization can be developed by a treatment at 500°C, after cold rolling and before recrystallization.&apos;

Jan 1, 1962

By AIME AIME

THE coal classification session* on Monday morning, Feb. 17, was opened by a paper by M. R. Campbell, entitled "Natural Groups of Coal and Allied Fuels," in which he pointed out, by means of graphical presentation of selected proximate analyses of coal, that coals can be classified on the basis of their moisture content. He proposes four groups of coal, brown coal, hydrobituminous, bituminous, and anthracite, each subdivided into two or three sub-groups. In a written discussion of this G. H. Cady, of the Illinois Geological Survey, showed that there is, in general, a progressive decrease in the moisture of Illinois coals from north to south, and that it would be very difficult to draw any arbitrary line dividing the coals of the State into two groups on the basis of moisture content.

Jan 1, 1930

By U. C. Tainton

The paper reviews the evolution of electrolytic zinc, describing some of the major obstacles that have been encountered and overcome. The chief remaining limitations of present-day standard practice are: Difficulty of obtaining high extractions, especially from low-grade and complex ores; filtration troubles, if ores contain much soluble silica; and irregularities in electrolysis, if more than certain limited amounts of antimony, arsenic, cobalt; etc., are present in the ores. These factors dictate a relatively high-grade plant feed, thus subjecting the electroytic-zinc process to the same kind of limitations as the zinc smelter. The "high acid process," in which both acid strength and current density are raised to about four times the usual figures, is described. This system concentrates both plant and operations, allows a simple type of flow sheet, and. minimizes some of the difficulties above mentioned. The large-scale operation of the process is described. SOME time ago, at a meeting of the Institute Prof. J. W. Richards1 said, "I take exception to the statement that all the factors in the production of electrolytic zinc were known long ago. There is possible in my opinion an improvement of perhaps 50 per cent. in the new electrolytic processes." An examination of the literature of the subject will show the justness of Professor Richards&apos; contention. The work of the earlier investigators was carried on in the shadow of difficulties that, today, are hardly more than memories. We seldom hear now of zinc sponge, that bête noir of the electrolytic-zinc pioneers. Zinc sponge, was the name given to a peculiar, soft, black, non-adherent form of zinc deposit that was utterly useless for melting into ingot form. At the big plant at Cockle Creek, New South Wales, in 1897, Edgar Ashcroft2 said that the solution in the plant would suddenly, and without ascertainable cause, go "bad" and begin to deposit spongy zinc. The most delicate, even spectroscopic, methods of analysis were unable to detect any difference between "good solution and "bad" solution; either form might change to the other on being kept for a while. When it is added that an outbreak of this insidious disease (which. appeared to

Jan 2, 1924

By J. H. Scaff, J. E. Kunzler

The measurement of the electrical, thermal, and magnetic properties of metals at low temperatures, primarily in the range of liquid helium below 4.2°K, is a powerful tool for investigating many of the fundamental properties of the metallic state. Such measurements also have many practical applications, particularly as an analytical tool. One example of the practical utility of such measurements is illustrated by a short study we have made of the low-temperature resistance of copper used in preparing varistors. Copper-oxide varistors are prepared by the thermal oxidation of copper. This results in the

Jan 1, 1959

By Maurice Cook

NORMALLY the grain size of cold-rolled and annealed copper sheet is of the order of 0.02 to 0.06 mm., and 0.1 min., for example, would, for many purposes, he regarded as undesirably large. The occurrence of very large grain sizes in a few isolated cases of copper sheet led the authors to inquire into the causes giving rise to such unusual results. During the course of this work a very large number of experiments have been carried out to determine the effect of varying the conditions of the final and penultimate rolling and annealing operations, as well as of earlier rolling and annealing treatments. A correspondingly large number of observations have been made, but within the space of one paper it is possible only to outline relatively briefly what appear to be the more important of these experiments and observations. The presentation of the results does not follow chronologically the order in which the experiments were carried out and they have been rearranged for the sake of simplicity. In recent years a considerable amount of work has been done in connection with the recrystallization and grain growth in metals and alloys that take place on annealing, and a number of generalizations have been reached. It is known that the crystal size in wrought material in the annealed condition depends on a number of factors, including the time and temperature of the annealing operations and the nature and amount of cold-work to which the material has been subjected. Results, however, that are not covered by these generalizations can be obtained, which, in some instances, may even appear to he contradictory to them. According to these generalizations gradual changes in grain size are effected by progressive variation of the factors involved in annealing or cold-working. The work recorded in the present paper, however, relates to the development of grain sizes which are far beyond those normally encountered in ordinary annealing operations and far in excess of grain sizes which, according to ordinary standards, would be classified as coarse or large.

Jan 1, 1938

By A. H. Cottrel

SINCE metallurgy exists to provide strong, tough, engineering materials it must inevitably be perpetually concerned with the problem of brittle-ness. The steel-making industry was created because chemically unrefined iron is brittle. The steel-working and alloy-steel industries exist partly because hardness and ductility are mutually exclusive qualities in structurally unrefined steel. Yet, in spite of these immense industries, the brittle failure of steel ships hulls, bridges, pressure vessels, and pipelines, is still a contemporary problem. In fact, brittleness is a normal property of most solids, including metals and alloys, at low temperatures. Only face-centred cubic metals are commonly ductile at the lowest temperatures, and even here exceptions are known.&apos;," Expensive are-melting processes. under inert gases or vacuum, have been developed to overcome brittleness in titanium, zirconium, columbium. and molybdenum. Polycrystal-line zinc, magnesium, and uranium have little ductility at room temperature. Beryllium, chromium, and tungsten have even less; similarly for antimony, bismuth, germanium, silicon, intermetallic compounds, and metallic carbides, nitrides, silicides, and borides. Oxides and other ceramics would be ideal creep-resistant materials but for their extreme brittleness when cold, and great efforts have been made to overcome this problem by mixing ceramics with metals. In fact, the traditional use of the name metallurgy for what is really the science of engineering materials is a recognition that most non-metallic solids have so far been precluded, by their extreme brittleness, from use as major structural materials in mechanical engineering. Most of what we know about brittleness in metals has come from studies of structural steel, and it is this material that shall mainly be considered. The things we have learned from it have a wider application, at least to other body-centred cubic transition metals, although the extent to which similar ideas can be applied to hexagonal metals and other materials is not yet clear. Fracture and Plastic Deformation The theoretical breaking strength of an ideal solid, about E/10 where E is Young&apos;s modulus, has been approached reasonably closely in experiments on fibres. But large specimens break at much lower stresses. For example, brittle cracks in large structural steel assemblies have been observed to spread catastrophically at speeds of 6000 ft per sec under stresses of about 10,000 psi, i.e. about E/3000. There are two sources of weakness; stress concentrations, and chemical agents in grain boundaries or on crack faces that lower the surface energy y of the material. Although we shall deal mainly only with the first of these, much of the discussion is also applicable to the second when different values of y are used. Griffith&apos;s well-known formula p = [ 2Ey/p(1 - v2)c]1/2 [1] gives the smallest tensile stress p able to propagate an atomically sharp surface crack of length c or interior crack of length 2c through a thick plate (compared with c) of elastically isotropic material of

Jan 1, 1959

By N. Tiner

THE mechanical properties of magnesium-alloy castings are greatly improved by grain refinement, and at present considerable attention is being paid to methods of obtaining fine-grained castings. One method of achieving this end is the use of proper melting and superheating techniques. These have been employed commercially to a great extent, but no comprehensive study of the subject appears to have been published at present. Numerous investigations found in the literature include some reference to superheating techniques, 1-4 and Achenbach, Nipper and Piwowarsky,5 based principally on thermal analysis, ascribe the grain-refining action of superheating to the influence of solid foreign particles or dissolved gases present in the melt upon the course of crystallization. The primary purpose of this paper is to present the principal facts concerning the effect of superheating on grain size of magnesium alloys. Attempts are also made to explain the experimental results in terms of a general hypothesis. The investigations are limited chiefly to common commercial casting alloys. In order to carry on this work, it was necessary to determine the factors influencing grain size and to develop a proper technique for the preparation of samples. The preliminary tests made by the author indicated that the grain size of magnesium alloys resulting from the solidification of a melt is determined by alloy composition, presence of impurities, rate of cooling during solidification, thermal history of the melt and to some extent the structure of the charge used. The rate of cooling is in turn dependent upon the mass of the melt, pouring temperature, and dimensions, properties and temperature of the mold into which the melt is poured. The final grain size of the alloys is still further modified by heat-treatment subsequent to casting. It is not within the scope of the present paper to discuss all of these factors, and it would suffice to note here that when equal amounts of magnesium alloys are prepared from the same alloying materials, melted in graphite crucibles under the same thermal conditions, then cast into graphite molds at a constant temperature, the .resultant solids have the same grain size. By maintaining all other factors constant, it is thus possible to vary thermal conditions of a melt and to examine the grain size of resultant castings. PREPARATION OF SAMPLES AND GRAIN-SIZE TESTING The alloys investigated in this paper were taken from ingots made by Permanente Metals Corporation or prepared by the author with pure carbothermic magnesium and necessary alloying elements. Melting was carried out under a flux in a graphite crucible heated uniformly by an

Jan 1, 1945

By A.J. PHILLIPS, Wm. B. Price

ADMIRALTY nickel is a new corrosion-resisting and heat-resisting white metal alloy composed of 70 per cent. copper, 29 per cent. nickel and 1 per cent. tin. It has been given the trade name "Adnic." In 1924, Win. B. Price1 described this alloy and its successful use as a diaphragm metal. The physical properties of Adnic at ordinary and elevated temperatures were given in Mining & Metallury.2 A patent3 was granted on Adnic, April 28, 1925. Work was first started on this alloy during December, 1921. An investigation of the patent situation in this country and abroad, and also a search of the literature, did not reveal any work on the ternary diagram, copper-nickel-tin; and the only wrought copper-nickel-tin alloy found was that known as "Newloy," composed of copper, 64 per cent.; nickel, 35 per cent.; tin, 1 per cent. This was being manufactured and sold by Wm.. Gallimore & Sons, Ltd., Sheffield, England, for unplated spoon and fork stock, and first came to our attention in January, 1922. The preliminary work in connection with the development of Adnic was started by casting four, binary copper-nickel alloys of the compositions shown in Table 1. Various amounts of tin were added to each of these mixtures, to produce the series of ternary copper-nickel-tin alloys also given in Table 1. A 200-gm. sample of each of these was cast by melting in a clay graphite crucible and allowing the melt to slowly cool with the furnace. A longitudinal section from each of these castings was polished and etched for-examination. The castings were not homogeneous solid solutions, but showed the usual cored structure associated with cast alloys. However, from an examination of these sections we roughly determined

Jan 1, 1928

By M. J. Pool, J. R. Guadagno

THE relative partial molar heats of solution in liquid tin have been determined for phosphorous, arsenic, and antimony at 750°K. This work was carried out as part of an over-all program to determine the heats of formation of the III-V semiconducting compounds. A differential twin-type liquid tin solution calorimeter was used in the investigation. All three elements are endothermic upon solution in tin. The relative partial molar heats of solution go through a minimum value at arsenic. No concentration dependence of the heat of solution was found in the dilute (0 to 2 at. pct solute) solution range investigated. The measured heat effects and the calculated relative partial molar heats of solution at infinite dilution are listed in Table I along with the relative heat contents of the solutes calculated from the data of kelley.1 All of the values are referred to 750°K even though the calorimeter temperature fluctuated by *1°K during the course of the experiments. In this range of temperature change no variations were found which were outside the experimental error. This would be expected since the partial molar heat of solution is in general a very insensitive function of temperature. The limits of error given in Table I represent the standard deviation from the mean. The reported error estimates only apply to the estimated precision of the data and not the accuracy. Systematic errors could be present which would affect the absolute values given. This is especially true in the case of phosphorous and arsenic where vaporization could occur. If this were true, the experimental values reported here would be too high and the true partial molar heat of solution would be less than that given in Table I. Moreover, the heat-content data could be in error and this would also affect the calculated values. The relative partial molar heat of solution of phosphorous at infinite dilution in liquid tin is given in Table I. This value is based on eight drops at

Jan 1, 1965

By A. M. Adair

The effect of cathodically charging zone-refined iron with hydrogen and the resultant yield stress-grain size relationship has been investigated by tensile testing at -31°C. The resulting Petch plots (using a least-squares analysis) reveal a significant reduction in the slope and an increase in the intercept for specimens cathodically charged with hydrogen, regardless of whether the hydrogen is present during testing or is removed by evacuation. Other than surface blistering, the major effect of cathodically charging this material is to create occasional grain boundary cracks and thus presumably a large number of free dislocations at grain boundaries. These results are consistent with the hypothesis that the slope of the Petch plot is related to the stress required to activate dislocation sources at or near pain boundaries. While there is no significant effect of the presence of hydrogen on the lower yield stress of this material, the ductility is considerably reduced. After hydrogen removal by evacuation, the ductility recovers substantially and almost complete recovery of ductility is experienced by the smaller grain size specimens. THE influence of hydrogen on the mechanical properties of ferritic materials has received much attention throughout the history of the metallurgy profession. This interest has stemmed from the obvious importance of preventing the catastrophic failure of parts in service, and from the desire to determine what mechanism is responsible for the observed behavior. The various mechanisms proposed for hydrogen em-brittlement have been discussed in detail by Tetel-man,&apos;who concludes that a combination of the applied stress and hydrogen pressure within voids best accounts for the many experimental observations reported. From a quite reasonable correlation of the strain aging and delayed-failure behavior of a variety of materials,2-7 Troiano and coworkers are of the opinion that the delayed-failure mechanism (slow strain rate embrittlement as well) is better explained as a lattice effect; solute elements diffuse to regions of high triaxial stress, form uncondensed atmospheres there, and effect a reduction in the cohesive strength of the lattice. Since hydrogen yield points8,9 have been observed in ferritic materials, and since the hydrogen embrittlement process may be related to strain aging, one further contribution to embrittlement could be hydrogen-dislocation interactions which make crack blunting by plastic deformation a more difficult process. The etch" relationship offers a means of comparing the relative ease of initiating and propagating plastic deformation in metals and alloys. In the present study, this relationship was used to compare the behavior of zone-refined iron in three conditions: uncharged, cathodically charged with hydrogen, and cathodically charged with hydrogen and evacuated. These Petch plots and the observed ductility parameters allowed a separation of the effects of the very presence of hydrogen and the act of cathodically charging hydrogen into this material. MATERIALS AND EXPERIMENTAL PROCEDURE An ingot of zone-refined iron was obtained from Battelle Memorial Institute which contained the following (typical) interstitial impurities in ppm: carbon, 10 * 5; nitrogen, 1; oxygen, 22; hydrogen, 0.9. The ingot was cold-reduced to a 1/2-in.-sq cross section, recrystallized 1 hr at 575°C, and then straight-rolled to a thickness of about 0.105 in. Tensile specimens were milled from the strip having a 1-in. gage length

Jan 1, 1967