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By N. H. Fisher

Geographical Distribution 'he most important known deposits in Australia of what are commonly referred to as the beach-sand minerals are along the most easterly part of the Australian coast, between Southport, 17 miles north of the Queensland-New South Wales border, and Ballina, 50 miles south of the border, and most of the production has come from this area (Fig I). Smaller deposits are known to occur farther to the south at intervals for several hundred miles, and beaches have been worked at Yamba, 96 miles south and Woolgoolga, 150 miles south of the border and at Swansea, 60 miles north of Sydney. Important deposits have been shown to exist on north Stradbroke Island and others have been located farther to the north, as far as Tin Can Bay at the south end of Frazer Island. (Fig 2). Table I gives the list of operators with the location of their deposits and workings, their approximate maximum monthly capacity expressed in tons of heavy mineral produced by their concentrating plants before separation into individual mineral concentrates, their methods of mining and concentrating the minerals, and the products obtained. This table applies as of June 1948, but all the operators are remodeling or improving their plants and plant practices will be modified accordingly. In addition, active boring campaigns have been carried out by Alluvial Gold, Ltd., of Sydney, in the Cudgen-Cudgera area, and by Zinc Corporation Ltd., of Melbourne, on Stradbroke Island, and in other places. Physiography Submergence of the order of 100 to 200 ft at the close of the Pleistocene period left the pre-existing hills as promontories and the valleys as deep inlets. Wave action has built bay-bars and sandspits in a northerly direction from the headlands, and lakes and marshes have formed between these bars and the initial post-submergence coast line. These lakes and swamps have been or are being filled in by river-borne sediments or wind-blown sand. Beasley1 has presented evidence that suggests a recent emergence of the coast line of about 10 ft. The evidence for this belief is the presence of a black sand seam 1/3 mile inland and 17 ft above sea level (Fig 3), and although it is not entirely certain that this seam is of beach formation and owes nothing to windblown concentration, other evidence supports the suggestion of recent emergence. Such emergence would undoubtedly aid the formation of bars and sandspits and the easterly progress of the beach front, leaving a series of parallel dunes (Fig 4). This belt of north-south coastal dunes ranges up to 56 mile in width and as many as 15 lines of dune have been counted (Fig 3). The foredune is generally the highest, upto 25 ft high, and there is in many places a flat platform in front of the dune known as the berm. The dunes behind the foredune are lower and less well defined

Jan 1, 1949

By Olin M. Hart

Uranium ores occur in the Lower Cretaceous Inyan Kara group of heterogeneously stratified fluvial and fluvial-marine sandstones in the Black Hills of western South Dakota and northeastern Wyoming. There are three principal mining districts, each in the ancestral and present drainage area of a major river partially responsible for stripping the region to its present topographic form. Primary minerals in the deposits are coffinite and uraninite with minor amounts of paramontroseite and haggite. The ore minerals coat sand grains and fill interstices of complexly cross-stratified sandstone along solution fronts similar to "roll" type deposits of the other districts. Minerals of oxidized deposits are typically carnotite and tyuyamunite with different proportions of secondary vanadium accessory minerals. Ground water was the transporting medium and deposition of primary uranium and vanadium minerals occurred in reducing environments produced and controlled by physio-chemical characteristics of the sedimentary rocks.

Jan 1, 1968

By N. A. Tiner

A study was made of the effects of temperature, type of loading, and electric polarization on the fracturing behavior of copper and zinc coated with mercury. Copper showed an em-brittlement only in cyclic loading, whereas zinc showed an em-brittlenzent in both static and cyclic loading. The embrittle-ment of zinc in static loading was prevented by sub-zero cooling to a temperatzcre of about -70°F. The emhrittlement of both metals was sliglztly reduced by cathodic polarization of mercury. The basic processes involved in fracturing were discussed in the light of these observations. When a solid metal is in contact with certain liquid metals possessing high wetting characteristics, a weakening effect is produced, and the solid metal fractures in brittle manner at a relatively low stress. This lowering of the fracture stress generally is considered different from the stress cracking caused by a corrosive liquid environment and is attributed to the lowering of the solid-liquid interface tension at the grain boundaries.1-4 The purpose of this paper is to describe a number of observations on the special features of fracturing of copper and zinc coated with a liquid mercury film, and to analyze the basic processes involved in fracturing in the light of these observations. EXPERIMENTAL OBSERVATIONS I) Effect of Type of Loading—The evidence appears to indicate that in static loading, metals usually fracture by the initiation of microcracks in the interior preferentially at the grain boundaries or at the intersection of slip bands.' In cyclic loading, cracks develop on the surface within the active slip zones, and gradually propagate with increasing num- ber of cycles.6'7 Because of this difference in the manner of initiation of cracks, a series of bare and mercury coated copper and zinc specimens was subjected to static and cyclic loading, and their fracturing behavior was examined. The specimens were machined to 0.25 in. in diam and 1 in. in length from a high-purity commercial bar stock, and annealed at an appropriate temperature. Mercury was applied to the surface of the specimens by rubbing with cotton wool soaked in a saturated solution of HgCl2 or by etching with a dilute solution of HC1 and rubbing with purified mercury and by washing in water. The static tension load-extension curves were obtained by means of a Riele Screw Power Universal Testing Machine. The room-temperature load-extension curves for copper and zinc are shown in Fig. 1. The deformation behavior of copper, as judged from the general configuration of the load-extension curve, was not affected by mercury coating. The maximum load to fracture and the elongation at the maximum load were practically the same for both specimens. The mercury coated copper, however, showed somewhat less localized necking and had smaller reduction of area than the uncoated metal. The behavior of mercury coated zinc was radically different from the behavior of uncoated metal. The load-extension curves were the same at the

Jan 1, 1962

By Robert Maes, Robert de Strycker

The Cu-Sn-As systeM was studied in the region near the Cu-42 and (214-As binary diagrams, where reactions in the solid state appear, resulting from the decomposition of the y(Cu-Sn) phase and from the formation of the 7 phase (Cu,As). The techniques used were microscopic observation, thermal analysis by dilatometry, and X-vay diffraction. The formation of the 7 phase gives rise to a ternavy pevitectoid veaction; the decomposition of the y phase gives rise to five transitional reactions. The temperatures of almost all these reactions could be determined; in the most favorable cases , the accuracy of this determination was of 11.5-C. The 7 phase is stabilized by tin additions, the arsenic atoms being replaced by tin atoms up to 35 pct; this has allowed the preparation of pure j) phase and the confirmation, by extrapolation, of the conrposition of this compound in the Cu-As diagram. In the first part of this work, the solidification reactions in the Cu-Sn-As phase diagram were studied. In the copper corner, the structure of the alloys presented the evidence of reactions in the solid state: on the one hand, all the alloys containing the y phase of the Cu-Sn diagram showed, under the microscope, that this phase had formed different decomposition products after complete solidification; on the other hand, the appearance of the 7 phase of the Cu-As diagram necessitated the introduction of a peritectoid formation reaction. The study of the decomposition of the y phase has been done by preparing about forty alloys that were homogeneous y at high temperature. The formation of the 7 phase has been studied by means of a few alloys with a composition near the homogeneity field of this phase at room temperature. The part of the Cu-Sn phase diagram of interest for this study is represented by Fig. 1, with the phase designation which will be used in the remainder of this paper; it is drawn after Hansen and Anderko.' The Cu-As diagram has already been presented in Part I of this work; the significant features of this study are the existence of the arsenides CusAs and Cu5Asz, and the formation of a compound CUEAS, designated as the 7 phase, by a peritectoid reaction at about 325°C. EXPERIMENTAL METHODS The fundamental technique for the investigation of this part of the Cu-Sn-As constitution diagram was microscopic observation; the greatest part of the observed alloys has also been subjected to thermal analysis by dilatometry; a few selected alloys have then undergone an X-ray analysis by powder diffraction. Alloy Preparation. The alloys were prepared from the same products as in Part I of this study: cathode copper, arsenic with a purity better than 99.5, and tin with a purity of 99.98. The fusion of the ternary alloys was realized from

Jan 1, 1967

By A. A. Bauer, F. A. Rough, G. H. Beatty

AS a result of recent studies, the constitution of the zirconium-uranium system has been fairly well defined. A diagram for the system is shown in Fig. 1. However, both oxygen and nitrogen are known1-3 to have a pronounced effect on the limits of both ß- and e -phase regions. It has been shown that small amounts of oxygen severely constrict the compositional limits of these phase regions in the ternary zirconium-uranium-oxygen system. A previously published tentative diagram shown in Fig. 2 illustrates the ß-phase constriction resulting from oxygen additions. Generally, iodide zirconium has been used in constitutional studies of zirconium-uranium alloys. While this is the highest purity material available, cast iodide zirconium-uranium alloys will generally average from 200 to 300 ppm 0 and from 50 to 60 ppm N. Thus, while the constitution of the zirconium-uranium system is fairly well defined, it must be realized that this definition applies to alloys containing in the vicinity of 250 ppm 0 and 50 ppm N. The present investigation was undertaken to accurately determine the boundary between the ß-plus-P and ß phases at a single temperature in the binary zirconium-uranium system by quantitatively

Jan 1, 1959

By Thomas L. Watson

A part of the field-seasons of 1900, 1901 and 1902 mas devoted by the writer to a study of the manganese ore-deposits of Georgia. A report embodying the results of this study is rapidly nearing completion, and when finished it will be published as a bulletin of the Geological Survey of Georgia. I believe, however, the importance of these deposits warrants a separate and earlier publication than that made possible by the Survey, in which the more important results of the study are briefly set forth. It is principally for this reason that the present paper has been prepared. Previous Work.—Some of the more important deposits of manganese occurring in the Paleozoic area of Georgia were studied to some extent previous to 1890 by Dr. Penrose;t and again in the early nineties by former State Geologist, J. W. Spencer. In a recent paper published in the Transactions, on the " Geological Relations of the Iron-Ores in the Cartersville District, Georgia," Dr. Hayes briefly mentions the manganeseores of the same district. Distribution of the Manganese-Ores.—Georgia is divisible into three geologically-distinct areas which, named in order from southeast to northwest, are (a), the Coastal Plain; (b), the Crys-

Jan 1, 1904

McCulloch, Leon.-Experiments with Sherardizing. Discussed by Fred. L. Wolf, Willis M. Peirce, Jesse L. Jones, O. W. Storey, David R. Kellogg, William H. Finkeldey, L. H. Marshall 2 Bassett, W. H. and Davis, C. H.-Spectrum Analysis in an Industrial Laboratory. Discussed by C. S. Brainin, C. H. Davis, W. H. Bassett, George K. Burgess, George K. Elliott, Leonard Waldo, Keivin Burns 8 Roast, Harold J. and Pascoe, Charles F.-Arsenical Bearing Metals. Discussed by Jesse L. Jones, William A. Cowan,. William K. Frank, William M. Corse, Harold J. Roast 10 Bain, Edgar C.-Crystal Structure of Solid Solutions. Discussed by Ancel St. John, Edgar C. Bain, Paul D. Merica 14 Peirce, Willis M.-Studies on the Constitution of Binary Zinc-base Alloys. Discussed by George K. Burgess, Willis M. Peirce, D. H. Ingall, J. L. Haughton, K. E. Bingham 16 Webster, William R.-Application in Rolling of Effects of Carbon, Phosphorus and Manganese on Mechanical Properties of Steel. Discussed by George B. Waterhouse, J. O. Liebig, Ralph H. Sweetser, H. T. Morris, F. D. Carney, W. P. Barba, John H. Nelson, George K. Burgess 19 Barba, W. P. and Howe, Henry M.-Acid Open-hearth Process for Manufacture of Gun Steels and Fine Steels. Discussed by W. J. Priestley, Haakon Styri, C. T. Patterson, Harry Brearley, W. P. Barba, George F. Comstock, Alexander L. Feild 24 Kellogg, David R.-Electrolytic Deposition of Iron for Building up Worn or Undersized Parts. Discussed by Jesse L. Jones, William Blum, C. R. Hayward, George K. Burgess, C. P. Perin, David R. Kellogg 33 McQuaid, H. W. and Elm, E. W.-Effect of Quality of Steel on Case-carburizing Results. Discussed by H. J. French and L. Jordan, W. J. Priestley, M. H. Schmid, A. E. White, H. J. Stagg and S. C. Spalding, Henry S. Rawdon, J. S. Vanick 35 Phillips, Arthur and Davenport, E. S.-Malleableizing of White Cast Iron. Discussed by Samuel Epstein, H. A. Schwartz, A. E. White, R. S. Archer.... 58 Priestley, William J.-Effect of Sulfur and Oxides in Ordnance Steel. Discussed by Harry T. Morris, William J. Priestley, C. P. Perin, James H. Gray, W. P. Barba, Haakon Styri, Frank D. Carney, W. L. Harbrecht, George F. Comstock, E. J. Janitzky 67

Jan 5, 1922

By F. V. Lenel

Two years ago in Chicago a seminar was held on the theory of sintering of pure metal powders. As an introduction to this seminar D,.. Rhines1 gave an excellent survey of the literature on this subject, His method of presentatioll was to summarize the experimental observations on sintering and from them to develop a composite theory of sintering in which he combined all the important contributions to the theory into one organic whole. In contrast to the mechanism of sintering of pure metal powders, which, of course, al\vays takes place in the solid phase, sintering j,, the presence of a liquid phase, cannot be treated as one unified mechanism, such as the sintering mechanism of pure metals. The reason is that there are really several mechanisms depending upon the type of alloy system which is sintered and the field of its con. stitutional diagram ill which the sintering takes place, Two mechanisms have heen investigated and will be reviewed in this paper. Ill the first lnechanism the liquid is presellt during the entire time while the compacts are at the sintering temperature, In other words they are sintered between the liquidus and the solidus of the alloy system and are ~e~erogelleous during the entire sintering cycle. The second mechallism applies to alloys in which the liquid phase is formed during the sintering process, but disappears before the sintering process is completed through diffusion and formation of a solid solution. These alloys are therefore homogeneous at the end of the sintering cycle. This second mechanism is more complicated because of the two stages of sintering, the liquid and the solid, as they may be called. It is therefore not surprising that the few detailed investigations of sintering in the presence of a liquid phase have been concerned with heterogeneous sintered alloys, namely the tungsten-nickel-sinter ing which is the so-called "heavy alloy," and the cemented carbides. The mechanism of sintering of these systems is characterized by the fact that theoretical or near theoretical density is attained during sintering, while simultaneously a distinct grain growth takes place through solution of the smallest grains of the solid phase in the liquid phase and reprecipitation on the larger grains. In the first part of the survey this sintering mechanism which is called for short the heavy alloy mechanism is treated in detail. In the second part Of the survey experimental observations for the sintering of homogeneous sintered alloys where the liquid phase disappears before the completion of sintering are discussed. Much less systematic work has been done on these alloys to which the conlmercially important Porous bronzes and the iron-nickel-aluminum permanent magnet alloys belong. Emphasis will be laid throughout this survey upon the microstructural and density changes during sintcring because the Sintering mechanism can usually be described directly by these changes. Other

Jan 1, 1949

By James W. Shaffer

Aluminum is the most abundant metallic element and forms 8% of the earth's crust. Because of its chemical activity it does not occur in nature in a metallic form but principally in the silicates, feldspar, mica, shale, and clay. Bauxitic raw materials-bauxitic clay, aluminous laterite, and bauxite-develop from these aluminum silicate sources. Bauxite and aluminous laterite are naturally occurring mixtures of aluminum hydroxides and mineral impurities, and they are the major sources of aluminum. End Uses Bauxite is the basic ore of the aluminum industry. It is refined into aluminum hydroxide and calcined for feed stock to electrolytic smelters. Over 90% of the tonnage mined is refined and smelted into aluminum. The total tonnage consumed by other industries is small in comparison, but bauxite and alumina are important for the manufacture of refractories, ceramics, chemicals, abrasives, pharmaceuticals, catalysts, cements, dessicants, and flame retardants. Some aluminum-containing industrial products are made from clays and other materials but the majority originate from bauxite directly or from aluminum hydroxide and alumina refined from bauxite. Lateritic type bauxite is also used as building and decorative stone. Geology Mineralogy and Properties Bauxite is a mineral raw material composed principally of one or more aluminum hydroxide minerals and impurities of silica, iron oxide, titania, and other elements in minor or trace amounts. The important aluminum hydroxide minerals are gibbsite, boehmite, and diaspore. Bayerite, nordstrandite, and tucanite are naturally occurring aluminum hydroxides but are rare and not commercially important. Mixtures of gibbsite and boehmite are common, boehmite and diaspore less common, and gibbsite and diaspore rare. Gibbsite is aluminum trihydroxide. Boehmite and diaspore are aluminum oxide hydroxides and have essentially the same composition, but diaspore has a greater hardness and a more tightly bonded and denser atomic structure. Although not technically correct, the commercial terms trihydrate and monohydrate are frequently used to distinguish types of bauxite. If bauxite is all or nearly all gibbsite, it is referred to as a trihydrate ore; if boehmite or diaspore or a mixture of both are the dominant minerals, the bauxite is called a monohydrate ore. If substantial amounts of both gibbsite and boehmite are present, the bauxite is frequently referred to as a mixed ore. Properties of major bauxite minerals are shown in Table 1. Silica, iron oxides, and titania are major impurities always present in deposits of bauxitic raw materials.. Silica impurities usually occur as clay minerals, micaceous minerals, or quartz, but cristobalite and feldspar are found in some deposits. The most common clay minerals are kaolins; however, illites and chlorites are often found in small quantities. Varying proportions of aluminum, iron, and clay minerals make bauxite, aluminous laterite, ferruginous laterite, and bauxitic clay deposits gradational with each other. Hematite and goethite are the common iron mineral impurities in many bauxites. Magnetite and ilmenite occur in deposits derived from basic igneous rocks. Other iron minerals associated with bauxite are maghemite, pyrite, siderite, and marcasite. The titanium minerals found in bauxites are anatase, leucoxene, rutile, ilmenite, titaniferous

Jan 1, 1983

By Randall L. Neal

This paper discusses the impact of taxes at the state and federal level on typical on-shore oil and gas exploration economics in the USA. Taxes considered are the windfall profits excise tax, state production (or severance) taxes, state income tax, and federal income tax. Also considered will be market prices for oil and gas in the USA. The effect of government take as a percent of revenue, on rate of return, discounted Payout, and discounted cumulative cash flow is shown on the attached tables. The conclusion drawn is that tax laws, while rarely the most important factor to be considered when drilling a well, can have significant impact on the profitability of oil and gas ventures, and should be considered when determining where to drill. Hypothetical exploration wells were analyzed for the impact of tax laws on project profitability. The results of this study show that when factors other than taxes are postulated to be the same (such as producing rate, capital, operating costs, and prices), cash flow can vary by as much as 68% due to the differences in the tax laws. Other significant findings for the cases studied include: (a) that discounted payout varied by as much as 1.8 years, (b) that rate of return differed by up to 67% and (c) the total tax rate as a percentage of revenue had a maximum variance of 33%.

Jan 1, 1982

GRAHAM BRIGHT,* East Pittsburgh, Pa.-Bee-hive coke ovens are usually located at the mines, where the gases from the ovens are not strongly objectionable because the communities are not thickly built up. The byproduct oven will naturally he located near centers of industry, to which the coal can be brought from different directions and desirable mixtures can be made; where also the byproducts can be readily marketed, while the gas can be utilized for industrial and domestic purposes. Not much thought seems to have been given to the gases escaping from the byproduct coke oven, which are more or less objectionable in thickly populated sections. When the byproduct oven shall have been more widely installed, this question is likely to become serious, and it will be necessary to apply remedies. May I ask what has been done, or is going to be clone, in this direction? S. A. Moss, ? Lynn, Mass.-One cause of escaping gas is that the gas exhausters do not supply the proper suction. If a satisfactory regulating governor is applied and the correct kind of gas exhauster is used, the trouble will be eliminated. J. I. THOMPSON,? Pittsburgh, Pa.-The hoppers Co. has made a careful study of the question of smoke prevention. The smoke caused by the operation of the byproduct coke ovens is infinitely less than that caused by bee-hive ovens.

Jan 11, 1918

By Eugene McAuliffe

MANAGEMENT and control of any body of workmen can be effected through various - well-known methods ' though many managers hold certain personal theories of control that range from an absolute dictatorship to what might be called the principle of laissez faire, or the "let alone" method. Managements of many mines, factories, smelters and refineries have been compelled in recent years to accept certain restrictions in hours of labor as well as in methods employed, imposed either by federal or state laws, or by labor agreements. Broadly speaking, regulations of the above character were brought on the industry by managers who failed to recognize fully the rights of their employees to proper sanitary, safe, and compensatory working conditions, as well as working hours that were proper and just. As an example of poor management and worse psychology, we have only to hark back to the days when many bituminous coal operators maintained an inadequate number of pit cars for the number of miners or loaders employed, or if the pit cars were available, the haulage facilities

Jan 1, 1934

By Richard P. Rothwell

The communication which I hare to lay before my fellow-members of the Institute, is no elaborate paper, nor the statement of any great discovery; it is simply the record of convenient methods of conducting topographical survey?, and of keeping the notes of the same; methods that have grown out of practical experience, and have saved me many a day's labor by facilitating office and field work, and at the same time secured a greater degree of accuracy than is obtained by the methods now in general use. I assume it as granted that no topographical map is worthy of the name, except it represent the elevations and depressions of the surface by means of horizontal or contour lines. In the Ordnance Survey of Great Britain, the contour lines are traced for every fifty feet vertical height, I believe, by running out the line with level and compass through all its meanderings on the surface; this, of course, is a very tedious, though accurate process, but " in the woods," where many of our surveys have to be made, it would be practically impossible. Some time ago, I made an extensive and quite elaborate topographical survey and contour map of the southern portion of the Cahaba coal-field, in Alabama, the object of the survey being to

Nature: Man is but one of the creatures which in- habit the earth, a dust speck in the universe. Thinking man has been concerned with his place and purpose in the universe since the earliest Egyptian and Chinese philosophers. Ancient creeds, as well as modern religions and philosophies of life, were concerned with the same problem. While such considerations and concepts have been valuable, theoretical philosophizing and dogmatic concepts are inadequate for a satisfactory solution of world problems of today. The concepts of man and life and their ultimate purpose should be sought in the relations of intelligent man to man and their relation- ship to the physical world. The quintessence of nature's accomplishment-man- is also the greatest disturber of nature and the greatest enemy of his own kind. While his spirit and mind defy and overcome natural limitations, his physical self is controlled by the same basic biochemical laws that govern any other form of living matter. This paradoxical duality of human voluntary and involuntary relations to nature is the source of the perpetual conflict between mind and matter. Therefore, the higher the spiritual evolution and perfection of the individual's mind, the greater and deeper the conflicting elements in their expression; and conversely, the simpler the mind or the mental and spiritual heritage, the less is the individual concerned with the conflicting elements.

Jan 1, 1950

By A. M. Gaudin

It is only in recent years that substantial progress has been made in developing a physico-chemical picture of the solid state. The molecular concept, so useful in dealing with gases, was naturally carried over to the field of crystalline solids; it has resulted in the firm implanting of erroneous concepts that only now are being eradicated successfully. Two simply written and effective books on the subject are Crystal Chemistry by Stillwell' and An Introduction to Crystal Chemistry by Evans. A more complete treatment of the subject is available in a book by Wells. The monograph by Hucke14 also touches on a subject most easily perceived by reference to the brief introduction by Bragg; that master of the field. These texts make it clear that while some solids are built of molecules, many are built of ions, others of atoms connected in the form of giant molecules, and still others of cations and electrons. The various lattices in which these entities are systematically arranged, the joint use of several of these entities, and the transitional character of some of the bonds make for the great variety of crystalline solids. The purpose of this paper is to point out a most important corollary of present views on the structure of solids. In this connection the classification of solids in Table I is helpful.

Jun 1, 1955

By F. H. McDowell

For more than two hundred years Mexico has been enriching the world from her inexhaustible wealth of precious metals. From this source alone, over three thousand five hundred millions of dollars have been poured into the coffers of Europe and America. During these centuries the wants of the country in manufactured goods have been supplied from the mills and machine-shop of the Old World. English, French and German merchants in Mexico have vied with each other in their efforts to control the importing of these goods from their respective countries. The overthrow of Maximilian, the departure of the French and the restoration of the Republic, largely influenced by the strong stand taken by the United States Government during our own civil war, established a new order of things. Americans were encouraged to visit the sister republic, examine into the needs of the country, as well as its resources, and interest themselves in the work of development. More recently, under Presidents Diaz and Gonzales, liberal inducements have been extended to American capitalists to build railroads, open mines, erect reduction-works, raise cattle and improve the crude systems of agriculture. The Mexican Central Railway has been pushed south from the Rio Grande to the Capital, and, by its branches and connections, makes the whole mineral belt of the country accessible.

Jan 1, 1885

By A. W. H. Morris, E. A. Steigerwald

The jatzgue beizazriov oj Mietal matrix co))zpos~tes in tension -lensiom loading has been imestigated as a junction of Dolume fraclion veinfovcelnent using the model systems of a silver matrix reinforced with contlnuous or dzscontztinuous aligned tungsten jilamenls and continuous aligned steel filamenls. Appreciable impvocetnents in fatigue strength were obseved in all syslems inzvesLigated, the degree of sl renglhenng-increasing with increasing volume fraclion of reinforcement. The mode of fatigue failure was found to be a function of colutrre jp-actiotz and was also noted to be controlled by the relative fatigue and strength characlerislics of the matrix and reinforcemenl. THE advantages to be gained by suitably incorporating high-strength filaments or whiskers into metallic matrices are well-recognized.' To date emphasis has been placed on the experimental determination of tensile strengths and elastic moduli of metal matrix composites measured parallel to unidirectionally aligned filaments. Several attempts have been made to relate experimentally measured tensile properties to theoretical values calculated from the properties of the components on the basis of the relatively simple "rule of mixtures" analysis. However, relatively few data have been reported in the literature on the fatigue behavior and mechanism of fatigue failure of metal matrix composites. In a study of fatigue crack propagation in aluminum plus steel wires and aluminum plus tungsten wires, Forsyth et a1.2 found that the incorporation of small numbers of filaments suitably dispersed were capable of substantially reducing the rate of fatigue crack propagation. For this purpose, the strength of the filaments appeared to be more important than the aspect ratio and the authors reported that parallel filaments were not the most favorable orientation for increased strength. In a basic study of the fiber reinforcement of metals, Williams and 0'brien3 report preliminary results which indicate a considerable improvement in fatigue strength in reversed bending fatigue of a steel wire-reinforced aluminum alloy composite. In a study of the influence of interfacial bonding on fatigue behavior, Baker4 has also reported improved fatigue properties in stainless steel-reinforced aluminum composites. In contrast, Ham and place5 report that, although tensile properties are improved greatly by filament reinforcement, the reinforcement of copper with continuous, brittle tungsten wires up to 23 vol pct was comparatively ineffective against fatigue. The authors attribute the poor fatigue properties of the composite to fatigue hardening of the matrix at the tips of cracks which can build up stress concentrations sufficiently large to fracture proximate filaments. Baker and cratchley6 failed to find marked improvements in the reversed-bending fatigue properties of silica-reinforced aluminum. The study was complicated by the complex behavior in a composite during the compres-sive half-cycles imposed in this type of loading. This was manifested in the failure of the composites by de-lamination, a contributing factor being the presence of aluminum oxide at the matrix-filament interface. Prior to the general acceptance of filament-rein-

Jan 1, 1968

By C. H. Li, R. J. Stokes, T. L. Johnson

The effect of alumina particles on the nucleation and growth of cracks through a silver- chloride matrzx has been investigated. It has been found possible to promote fibrous cracking in dispersion-strengthened silver, chloride under notch-impact conditions at temperatures at which silver chloride alone cleaves brittlely The modification) of fracture beIzavzor is thought to be due to the relaxation of hydrostatrc stress beneath a notch by the nucleation of cavities near alumina particles. In recent years, composite or dispersion-strengthened materials have been studied primarily to understand their high resistance to plastic flow particularly at elevated temperatures. Dislocation models have been developed with which it is possible to deduce with fair success the effects of interparticle distance, particle size, temperature, upon yielding and creep behavior.l-4 Much less attention has been paid to the fracture behavior of these materials (with the notable exception of common structural steels) and little is known experimentally about the manner in which inclusions affect the nucleation and growth of cracks through a matrix. Nevertheless a beginning has been made in connection with fibrous cracking in ductile matrices where inclusions appear to play an essential ro1e.5-7 During the severe localized plastic deformation which accompanies necking in a tensile test, cavities are believed to develop at inclusions; these cavities subsequently grow and coalesce by plastic flow until separation is complete. It is of interest to consider whether inclusions can affect fracture behavior under loading conditions which restrict the plasticity of the matrix itself (for example, cleavage under conditions of a high imposed strain rate at low temperatures). It is particularly interesting to study these effects in a solid which shows a spectrum of behavior ranging from fully ductile to semi-brittle behavior. Such a solid is silver chloride whose mechanical behavior depends sensitively upon temperature and strain rate.'," The present paper is concerned with a study of the influence of inclusions (in the form of alumina particles) on the fracture behavior of silver chloride loaded uniaxially at low strain rates at room temper- ature and also under notch impact conditions over a wide range of temperature. In particular, it will be shown that the alumina particles can exert a startling effect on the ductile-brittle transition temperature of notched silver chloride and that the magnitude and nature of the effect depends upon both the quantity of alumina and the shape of the alumina particles. 1. EXPERIMENTAL PROCEDURE 1.1 Materials Used. Silver chloride powder of analytical reagent (AR) quality having an average particle size 6 was supplied by the Mallinckrodt Chemical Works (st. Louis, MO.). Acid washed 900 mesh alumina powder, designated A38-900, was supplied by the Norton Co. (Cambridge, Mass.). This powder was added to silver chloride in two forms: a) the as-received condition in which the individual particles were of random irregular shape; their statistical average size was 7; b) in a condition in which each particle was spherically shaped by a fusion technique. In this case, the statistical average particle size determined with the optical microscope was approximately the same (about 5p) but electron micrographic evidence indicated that many ultra fine particles were present in the spheroidized powder. 1.2 Preparation of Composite Materials. Silver chloride-alumina composites containing 2.5, 5, and 15 pct by volume of alumina were produced by the extrusion of mechanically mixed powders blended in a ball mill for 24 hr at room temperature. The mixtures were compacted at 50,000 psi at room temperature in the form of billets 3/4 in. in diameter and 1 in. long which were then extruded with a 16:l reduction ratio at 370°C through a radius-type steel die having a 5 deg lead-in angle. An extrusion temperature of 370°C was selected to ensure that all composites had sufficient plasticity to be extruded. Apart from this general requirement, the choice was arbitrary. 1.3 Microstructure of Composites. Attempts were made to check the distribution of alumina metallo-graphically by polishing transverse and longitudinal sections of the extruded rod. Specimens were wet-ground to 600 emery paper and lapped successively with 5 and 0.25-p grades of diamond paste. They were etched for 10 sec in 10 pct sodium thiosulfate solution and lightly polished in concentrated ammonium hydroxide. The most effective way to render the alumina particles and grain boundaries visible was to radiate the surface with intense white light to decorate the grain boundaries and the particle-matrix interfaces photolytically.

Jan 1, 1962

The Institute conducts jointly with the American Society of Civil Engineers, American Society of Mechanical Engineers and American Institute of Electrical Engineers, certain activities as listed below, and is joint owner with them of certain properties. United Engineering Trustees, Inc. When Mr. Carnegie made his gift which made possible a home for the engineering societies, a separate corporation was organized to act as a holding company and to manage the common property. This was long known as the United Engineering Society but the name has now been changed to one which more nearly reflects the real function of the corporation. It holds title to the Engineering Societies Building and to various funds placed in its charge and is managed by a Board of Trustees of which three are chosen by each of the four societies, American Institute of Mining and Metallurgical Engineers, American Society of Mechanical Engineers, American Institute of Electrical Engineers and American Society of Civil Engineers, which own equal and undivided interests in the property. The land and building cost two million dollars. The interest of each of the Founders societies, aside from especial trust funds, is now valued at $493,352. The A. I. M. E. trustees are Arthur S. Dwight, J. V. N. Derr and George D. Barron. The President of the Board is Francis Lee Stuart and the Secretary, Alfred D. Flinn.

Jan 1, 1923