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By S. R. du Toit, W. J. Oberholzer, M. I. Watson, D. G. Krige

The objectives, essential features and implications of the 'random' and 'deterministic' types of ore value surfaces are examined as well as the basic requirements for a satisfactory prediction model. The 'random' method used on the South African gold mines and based on observed auto-covariance patterns is briefly discussed as well as its justification in preference to the 'deterministic' approach. Various mathematical models for auto-covariance patterns are examined for the one-dimensional case. It is also shown that these patterns as estimated for ore values in certain mines agree closely for various sizes of ore unit. In two case studies the variations in gold, uranium and ore thickness covariance patterns are examined and compared with certain geological features established independently from sedimentological studies.

Jan 1, 1969

By J. Marshall Downey

The most fortunately situated U. S. potash producer-whether in New Mexico, California, or Utah--once simply took from the ground a mixture of sodium chloride and potassium chloride, crushed it to a maximum of 10 mesh, and separated the two salts by physical methods. He piled the sodium chloride on the desert and sold the potassium chloride to fertilizer mixing companies. Seven companies in the Carlsbad basin of New Mexico now use at least three basic processes for making the separation and at least three more processes have been or are under investigation. In addition, two companies outside the basin use two methods for taking KC1 from natural brines

Jan 12, 1958

By Leonard C. Grimshaw

Diffusion of carbon from gases into iron has been the object of much research, because of its long recognized importance in carburizing processes, but the direct diffusion of carbon from steel into iron has received relatively little attention. Because of the increasing use of clad metals in industry, direct diffusion from steel into iron is becoming of practical importance. Therefore, the object of this investigation was to study the diffusion of carbon from several different kinds of steel directly into relatively pure iron, realizing that elements in the steels other than carbon might influence the rate of carbon diffusion. The previous work on diffusion of carbon into iron has been considerable, and includes many reports in foreign languages. This work has recently been well reviewed by Mehll and Krynitsky12 and the reader is referred to their excellent bibliographies. Methods of Study There are two main methods by which the direct diffusion of carbon from steel into iron may be studied. In one method, steel is first decar-burized in part, and diffusion of carbon then allowed to take place from the steel into the decarburized steel. This method is open to two serious objections: (1) the decarburized steel is not iron, but contains elements such as manganese, silicon, chromium or tungsten, which may be an essential part of the steel under study, and which may seriously influence the diffusion of carbon into the decarburized area; (2) there is from the start of diffusion an unknown carbon-concentration gradient between the steel and the decarburized area. Another method, which possesses neither of these disadvantages, is to study diffusion from steel into a thick plating of electrolytic iron. Herc the chief difficulty is to secure an electrolytic deposit of iron upon steel without introducing an oxide film at the interface that will interfere with diffusion. The author is able to deposit iron upon any kind of steel without introducing an oxide film at the interface, so that diffusion of elements from the steel into the iron is free to proceed unhindered.

Jan 1, 1938

By Leonard C. Grimshaw

Diffusion of carbon from gases into iron has been the object of much research, because of its long recognized importance in carburizing processes, but the direct diffusion of carbon from steel into iron has received relatively little attention. Because of the increasing use of clad metals in industry, direct diffusion from steel into iron is becoming of practical importance. Therefore, the object of this investigation was to study the diffusion of carbon from several different kinds of steel directly into relatively pure iron, realizing that elements in the steels other than carbon might influence the rate of carbon diffusion. The previous work on diffusion of carbon into iron has been considerable, and includes many reports in foreign languages. This work has recently been well reviewed by Mehll and Krynitsky12 and the reader is referred to their excellent bibliographies. Methods of Study There are two main methods by which the direct diffusion of carbon from steel into iron may be studied. In one method, steel is first decar-burized in part, and diffusion of carbon then allowed to take place from the steel into the decarburized steel. This method is open to two serious objections: (1) the decarburized steel is not iron, but contains elements such as manganese, silicon, chromium or tungsten, which may be an essential part of the steel under study, and which may seriously influence the diffusion of carbon into the decarburized area; (2) there is from the start of diffusion an unknown carbon-concentration gradient between the steel and the decarburized area. Another method, which possesses neither of these disadvantages, is to study diffusion from steel into a thick plating of electrolytic iron. Herc the chief difficulty is to secure an electrolytic deposit of iron upon steel without introducing an oxide film at the interface that will interfere with diffusion. The author is able to deposit iron upon any kind of steel without introducing an oxide film at the interface, so that diffusion of elements from the steel into the iron is free to proceed unhindered.

Jan 1, 1938

By I. Lowthian Bell

THERE has been probably no improvement introduced into the manufacture of iron which created more surprise in the minds of practical smelters and of scientific men than Neilson's discovery of the hot blast. In 1829, Messrs. Dunlop & Co. consumed at the Clyde Works, near Glasgow, nearly 79 tons of coal to make a ton of pig iron, of which about 20 cwts. was employed under the boilers of the blowing engines, leaving nearly 7 tons for the consumption of the furnace itself. In the year 1833, by heating the air to 612' F. (322' C.), they redoccd the 79 tons to 3 tons by the mere burning of 8 cwts. of coal in the apparatus for raising the blast to this temperature. The statenlent just given is strictly true in a commercial sense, but when we come to consider the question as one of physical science, it is necessary to eliminate some of the conditions which conduced to so extraordinary a result. Anterior to Neilson's time the fuel employed in smelting iron was coke, and it was supposed at that period, erroneously, however, that coal in its raw state, when burned with cold air, was totsally unfit for the purpose in question. This mineral, as it was obtained from the Lanarkshire coal-field, contained about 35 per cent. of volatile matter, but the process of charring it was performed in so unskilful a manner that instead of receiving 88 cwts. of coke from 135 cwts. of coal, 60 cwts. only was the product of the operation. Again, the reduced colisumption of carbon in the furnace itself was accompanied by a corresponding diminution of blast, and this was followed by an economy of half a ton in engine coal. After making a proper allowance, however, for all these collateral circumstances, we are within the mark when we admit that in actual coke, which is really the form the fuel has to assume before it is burnt in the blast-furnace, not less than 30 cwts. was saved by heating the blast to 615° F. (322° C.). This unexpected economy, be it remembered, was obtained by the combustion of the 8 cwts. of coal, somewhat wastefully applied in the hot-air apparatus. Numerous have been the opirlions advanced by different authorities in the scientific world to account for the apparent anomaly, bat none,

By Robert Glass Cleland

THE DEATH of William E. Dodge occurred at a time when, all unwittingly, the company in which he had so long been the dominant factor was about to break with its old practices, its old traditions, its old interests, and transfer its major activities three fourths of the way across the continent and engage in an enterprise that differed almost as much from the original Phelps Dodge undertakings as the rough, arid mountains of the new region differed from the green hills and valleys of New England. To understand the effect of this transformation upon the fortunes of Phelps Dodge, one must change the setting of the present narrative from the familiar locale of the Atlantic seaboard to the land of "distance, silence, and solitude," that men called Arizona. In 1880 that Territory was one of the last frontiers of the Old West. To the Spaniards it had been a land of mystery and fable, the limit of the King's settlements, the far edge of the rim of Christendom. Through it Coronado; in a vain effort to find the fabulous Cities of Cibola, had led "the most brilliant company ever assembled in the Indies to go in search of new lands." Below its southern border, Father Kino, the "steel-thewed" Jesuit described by his

Jan 1, 1952

By T. E. Leontis, R. S. Busk

WORK was initiated several years ago at The Dow Chemical Company to determine the applicability of powder metallurgy processes to magnesium and its alloys. Although it was found possible to apply the normal techniques of compacting and sintering, it was discovered early that the technique of extrusion offered special promise. This technique and the alloys produced were therefore studied extensively, and the present paper is a partial report of those studies. It is expected that a second paper will discuss more extensively some of the alloy systems simply mentioned here. Although the literature on powder metallurgy is very extensive, there are only two articles dealing with magnesium13,14 and there is no reference to the direct extrusion of the powder of any metal without the preliminary step of compacting. Furthermore, no mention has been made of the possibility of designing alloys by the technique of powder extrusion, particularly alloys that cannot be made in any other way. Sauerwaldl3 discusses the extrusion of magnesium and aluminum powder to produce alloys containing nonequilibrium phases, but again he emphasizes the importance of pre-compacting before extrusion. There seems to be general agreement that some form of hot-pressing is essential to obtain in a compact the full theoretical density of the metal used.'-" The nearest approach to the technique of direct powder extrusion is that of extrusion of pre-sintered compacts,'-" for which the best review through 1944 is that by Kieffer and Hotop.11 Ensign* discussed a specialized technique of "extruding" already compacted and sintered gears for the purpose of sizing. Sauerwa1d13 discussed the compacting and extrusion of magnesium and magnesium-aluminum alloy band-saw chips. The properties of the extruded compacts were found to be comparable with those of extrusions prepared from solid billets. He also extruded a compacted mixture of magnesium and aluminum powder and found the properties to be somewhat different from those obtained on an extrusion made from a cast billet of the same composition. The second reference dealing specifically with the powder metallurgy of magnesium is Stern's patent," in which is described the extrusion of scrap chips and turnings following a hot-pressing and sintering step. Considerable emphasis in most of these articles is placed on the necessity of atmospheric protection to minimize the danger of oxidation. Experimental Procedure The first experiments were made with the small extrusion press shown in fig. 1. With this press, billets of about 1/2 in. diam are used to produce wire

Jan 1, 1951

By Gerald Sherman

LARGE part of the mining industry is still under the shadow of the depression, and unwilling to undertake changes in plant or methods of operation that require large preliminary expenditures of money. Certain metals command fair prices: nickel, tin, and molybdenum. The precious metals, gold and silver, have been given greater values by natural processes of economics or by proclamation, but are of so much less importance in industry, in total value, and number of men employed, that they have not greatly raised the average for the mining business. The increased value of gold which was established in 1933 has stimulated .the search for new deposits, and aided efforts to revive some of the old mines 'Where it is hoped to find quantities of marginal ore now become profitable. The higher price did not increase production very much for 1934, but two discoveries of major importance, and others yet to be proved, will help later. The two referred to are the Lupa gold field in Tanganyika Territory, and the Silver Queen mine on Soledad Mountain near Mojave in California. The first was recently discovered, and is being developed by the East African Goldfields, Ltd. Uncompleted explorations of the croppings early in the year had exposed for measurement and sampling to a shallow depth, three ore shoots as gregating 7400 ft. in length and 6 ft. in width, containing 0.375 oz. of gold per ton. In the Silver Queen. an ore-

Jan 1, 1935

By W. Rostoker, S. A. Spachner

FOLLOWING the discovery of the w transition phase in certain titanium-chromium alloys by Frost, Parris, Doig, and Schwartz, much interest has centered on the alloys in which this phase is found and its mode of precipitation. The w phase has been found in alloys of Ti-Cr, Ti-Fe, Ti-Mn, Ti-MO,2 and Ti-v.3 The temperature-time-transformation characteristics have, as yet, not been determined for most of these. In this study, such transformation characteristics have been investigated for two heat-treatable titanium alloys known to exhibit transition phase phenomena. The alloys chosen, Ti-8Cr and Ti-13M0, are representative of two classes of binary equilibrium systems. In the

Jan 1, 1959

By Gunnar Thaning, Borje Bjorkvall

At LKAB Central Division for Metallurgical Research at Malmberget, Sweden, fired pellets are examined in respect to mechanical and reduction properties. The paper deals with descriptions of the test methods. It also involves the rationale for the choice of these tests. Their correlation to the blast furnace operation will be examined. The mechanical tests used are the ISO-tumbler test and the cold compression strength test. Concerning the metallurgical properties, experiments have shown that some superbasic pellets in particular have different disintegration properties in different temperature ranges. Pellets which have favorable reduction properties when tested under isothermal reduction at high temperature may disintegrate to a large extent under low temperature reduction. This is also valid for some types of acid pellets. Consequently, it was found to be necessary to determine the reduction strength both at high and low temperatures. In the low temperature range, the disintegration is measured by tumbling the pellets in soft reducing conditions at 600°C in a modified Linder test equipment. The high temperature reduction strength is determined under load in the Burghardt-Grebe equipment. However, in order to get more information of the high temperature strength, LKAB intends to introduce a softening test. The tendency of high temperature disintegration will also turn up in the swelling test. The swelling properties are examined according to a procedure developed at LKAB. In this test the pellets are subjected to free swelling without mutual contact. The reducibility of the pellets is recorded in the swelling test.

Jan 1, 1974

By Richard L. Coleman

Metallurgical testwork to develop a flowsheet is described, beginning with background information required right through to a final process flowsheet. Both laboratory and pilot plant testing are reviewed with emphasis on the former.

Jan 1, 1978

By J. M. Dahl, R. J. Warrick, O. K. Riegger, H. Van Vlack

A liquid which is rich in oxygen (and silicon) develops at steel rolling temperatures in resulfurized and plain-carbon steels. This liquid fluxes solid manganese sulfide. The composition of the liquid and the resulting microstructures vary with the manganese/silicon/oxygen ratios in the steel. The observations and conclusions zuhich are presented are used 1) to suggest a mechanism for MnS deformation in resulfurized steels, and 2) to rationulize hot-shortness anomalies between plain-carbon and resulfurized steels. 1 HIS is a summary of the dependence of sulfide inclusion microstructures upon steel composition, and an interpretation of the behavior of sulfide inclusions at steel-rolling temperatures. Sulfide inclusions are known to have several metallurgical effects upon steel. Their effects upon hot-shortness are best appreciated. Although hot-shortness is well known, it is questionable whether its mechanism is fully understood because there are several anomalies in our interpretation. For example, why should not high sulfur contents produce extensive hot-shortness in free-machining steels ? A second metallurgical consequence of sulfide inclusions appears because sulfide inclusions improve machinability. Furthermore, globular inclu- sions are to be desired over elongated inclusions. To date, we know that lower silicon contents (< 0.010 pct) favor the globular sulfides, but we do not know why this interrelationship between silicon content and inclusion shape exists. Finally, the evidence is strong that the surface quality of a hot-rolled steel is particularly sensitive to the sulfur content. SUMMARY OF PREVIOUS WORK The role of sulfur in hot-shortness was first suggested during the past century. It is uncertain who was the first to conclude that sulfur was less deleterious in the presence of manganese, and that manganese altered the sulfide phase from a liquid FeS to a solid MnS at steel-rolling temperatures. However, Urban and chipman&apos; emphasized that liquid FeS may accumulate as an interdendritic film during solidification. More recently, Keh and Van lack&apos; showed that the intergranular liquid does not completely surround the metal grains at all rolling temperatures. Rather, a small finite dihedral angle exists when geometric equilibration is attained at

Jan 1, 1962

By W. H. Emmons

MANY mineral veins occupy faults, and movements on certain warped fault planes have resulted in openings. On normal faults the [ ] steeper parts have the widest openings, and on reverse faults the flatter parts have the widest openings. Theoretically the width of the opening is the sine of the angle of deflection times the amount of movement on the fault plane, but actually the widths of some of the openings are probably less because of readjustments of walls along joints or of other readjustments. The first treatment of the subject seems to have been in a book on mineral veins by John Leithart, published in Newcastle, England, in 1838. Later the subject was treated in various texts published in Germany, in England, and elsewhere. The subject was not given much prominence in the earlier American literature on economic geology, but has interested several workers in that field in the past decade. In this paper examples of districts showing ore shoots on warped faults, with relations noted, are described. Fault veins of the three depth classes of veins are noted. Many epithermal veins are in normal faults, and commonly the larger ore shoots are in their steeper portions. Many mesothermal veins are in reverse faults and many others are in normal faults. The flatter parts of veins in reverse faults are commonly wider than the steeper parts, although they are not always as rich as the steeper segments of the veins. There are not many hypothermal veins in faults of measured displacement.

Jan 1, 1943

CHARGING of an open-hearth heat is begun as soon as possible after the previous heat has been tapped. Ordinarily, about 40 min is required to drain and dress the furnace hearth, make up the taphole, and perform routine repairs of the banks. Repairs to the upper back wall and to the front wall and jambs can ordinarily be done while the first scrap charge is being heated and are therefore allowed to wait in order to save furnace time. Any major repairs required on the hearth or other parts of the furnace necessitate longer delays because such repairs must be made while the furnace is empty. Although charging practice varies considerably in detail with the type and proportions of scrap and iron used, many factors are common to all varieties of charge. Such general considerations are dealt with first. CHARGING EQUIPMENT AND STOCK HANDLING The physical equipment available for loading and weighing the stock, transporting it to the furnace, and charging it, may have a major effect on charging practice. Limestone, scrap, and all other solid melting stock are charged mechanically by means of equipment illustrated in Fig 2-1. The charging of hot metal is shown in the background of this figure. Mechanical equipment and plant layout for stock handling are described in Chapter 1. It is generally desirable to charge the scrap about as fast as the physical volume can be put into the furnace. Charging scrap that is too heavy or adding the charge too rapidly (less than 45 min) may be detrimental to melting rate because of excessive chilling of the entire furnace system and also because of poor conduction of heat to the lower layers in the furnace; but the more common problem is the reverse one of charging light &apos;scrap fast enough to maintain a normal heat time. A limiting factor may be the height to which the scrap may he piled in the fur-

Jan 1, 1951

By Frank L. Gaddy

Falls of roof account for over 50% of the fatalities that occur in coal mines in the US. Thus, roof control is one of the more important phases of underground mining. In reality, the control of roof influences the system of mining and is a major determinant of the width and spacing of working places, operations at the mining face, ventilation control, and surface subsidence. Frequently, the control of roof is the largest single cost item. Roof control is a never-ending task, not only at the working face and throughout sections where men are working, but along haulways and air- ways that must be maintained for the life of the mine. This is because roof, even the hest of roof, slowly deteriorates, so it must be frequently examined, with corrective support applied when needed. As coal is excavated, stresses are set up in the roof because the previous equilibrium is upset, resulting in pressures that cause fractures and slight movements that are frequently hard to detect. Unless the immediate roof, in the excavated area, is given support by artificial means, it might fall or there might be a succession of falls, varying from a thin scale to several feet, depending on the nature of the top. Exceptions to this are those rare mines, or sections of mines, with hard, strong, nonweathering roof that requires no support. GENERAL CLASSIFICATION OF ROOF There are two broad types of roof as far as support is concerned: the immediate roof above the coal and the main roof. Artificial support for mining purposes is only concerned with the immediate roof as nothing except large blocks of solid coal, or massive concrete, will support the main roof. The immediate roof is generally a few feet thick but call vary from inches to 6.1 m (20 ft) or more. There are examples of where there is no imrncdiate roof as the massive main roof lies directly on the coal

Jan 1, 1981

By T. C. Poulter, B. M. Caldwell, D. E. Brink

The flash X-ray has been used more than a decade to study the configuration of the jet from a shaped charge. The high-speed, rotating-mirror smear camera has provided time-distance graphs of detonations and shock fronts in transparent materials, and the high-speed framing camera has given pictorial representations of the progress of explosive phenomena. Adequate means for measuring the paths and velocities of all parts of the shaped-charge cavity Iiner during the collapse phase have not existed heretofore. A technique enabling the single-lens framing camera to make stereoscopic photographs of the cavity liner while it is collapsing has been developed. Analysis of this photographic record gives the directions and velocities of various parts of the Iiner surface, permitting direct quantitative measurement where this has previously been impossible. Significant improvements in shnped-clrarge design are expected to result. INTRODUCTION The familiar oilwell jet perforating charge, generally referred to as a "shaped charge", is related to the Mun-roe charge first described by C. E. Munroe in 1888 and later by Neumann in 1910. It differs in construction from the Munroe charge in that its cavity is lined with some inert material (usually metal)&apos;, and it differs in performance by projecting a fast jet of dense liner material against the target instead of a stream of expanding detonation products. Fig. 1 represents a typical shaped charge in axial cross section. The charge is circularly symmetrical about its longitudinal axis. The cavity at the right is lined with metal, usually copper; and, with the exception of air, the liner is otherwise completely empty. High-explosive material is intimately in contact with the convex surface of the liner and extends in the other direction to the booster. This is a pellet of high explosive having somewhat different characteristics and serves to couple the detonator to the main charge. When the detonator is fired, a small hemispherical reaction zone of very high temperature and pressure occurs at its output end. The booster responds, adding its own latent energy to the reaction, thereby initiating the main charge. The reaction progresses throughout the main charge at a velocity of 7 to 8 mm/microsecond until all the explosive material has reacted. With a reaction pressure of about 160,000 atm, the surrounding material is moved rapidly away from the high-pressure zone. As the detonation proceeds along the cavity liner, moving from apex to edge, the liner is collapsed toward the axis of the cavity, where liner material from all parts of the concave surface converges. A zone of extraordinarily high pressure results. with only one escape path—outward along the axis. The particles from the liner, thus, become a jet of very high velocity, with a density characteristic of the material from which the liner was made. The kinetic energy of the jet, concentrated in a small area of the target, has great penetrating power. It overcomes the strength of any target, and the target material crumbles or deforms plastically to escape from the path of the jet. An unlined cavity charge, on the other hand, projects a turbulent body of hot gaseous material against a target and erodes the exposed surface. With equal quantities of explosive, the penetration effectiveness of an unlined charge is a small fraction of that of a lined charge. Given an explosive charge with a detonator at one end and an axially symmetrical metal-lined cavity at the other, one has a perforator of considerable potency. To maximize the penetrating and other desirable effects,

By Alfred W. Gauger, George A. Burrell

The senior author of this paper, while in Colorado on other official business, made a trip to the Cripple Creek gold-mining district to get more data than are at present available regarding the composition of the gas that issues from the rock into the mines of the district. This was done at the suggestion of George S. Rice, Chief Mining Engineer of the Bureau of Mines. There are -many questions of interest and importance in connection with the ventilation of the mines in the Cripple Creek district, such as the menace to life and mining of a suffocating gas entering the mines from the rock, the danger due to powder smoke (from blasting operations), and danger of continued inhalation of rock dust by the miners. This report confines itself to the first problem, the gas from the rock, and principally to one phase of this question, the composition of the gas and its effects on men and lights. A more thorough study of this and other ventilation problems is planned. That the rock gas is a real menace is shown by the fact that miners (variously estimated from 25 to 50 by different persons interviewed) have been killed by it in the 25 years that mining has been vigorously carried on at Cripple Creek. Many men have had narrow escapes from death, some of them having been incapacitated for days. In addition, much loss of time results because at certain periods of the year or on certain days it is impossible to enter some workings. At a few mines, fans force air into the workings, thus supplementing the natural ventilation and much improving conditions, but the improvement is not entirely adequate at all times. Origin of the Gas Lindgren and Ransome1 think that the gas found in the rocks of the Cripple Creek mining district represents the last exhalations of the ex-

Jan 1, 1917

By D. M. Boulin, E. S. Greiner

Single crystals of vanadium were bent at 293" and 77°K to a maximum fiber strain of about 1 pct. Analysis of slip line and etch markings of- crystals deformed at either temperature show the slip planes are {112}. The slip directions at 298° and 77°K, deterwined from the asterism axes of rotation of crystals compressed in a {110} direclion, were (111). Etch pits, associated with dislocations, were observed in the plastically deformed vanadium. There was no evidence of mechanical twinning. THIS paper presents results on single crystals of vanadium plastically deformed by bending and compressing at 298° and 77°K. Bcc metals have been observed to slip on {110}, (1121, and (123) planes while the slip direction has invariably been found to be ( 111) 1 Lindley and smallman2 have studied the deformation intension of polycrystalline vanadium between 298° and 20°K and reported that at and above 77°K the deformation is predominantly by slip, but at 20°K the deformation is associated with twinning. Later, Edington and smallman3 found that single crystals of vanadium compressed in a (111) direction at 77°K deformed by twinning on { 112}( 111) systems. Clough and pavlovic4 have reported that mechanical twins were observed in vanadium loaded by impact at 77°, 173°, and 195°K, respectively. PREPARATION OF SINGLE CRYSTALS The vanadium single crystals were made from commercial vanadium reported to contain 0.03 pct C, 0.03 pct 0, 0.02 pct N, 0.0X* pct Ca, 0.0X pct Si, proximately 0.8 cm diam, 4 cm long and were grown in (100) and (110) directions. A crystal for studies of etch pits was gound to have a face parallel to a {l00} plane by the Bond crystal-orienting technique.7 In order to avoid straining, the crystals were placed on the steel mount with a low-melting organic compound (glycol phthalate) before grinding. Crystals for the bending experiments were ground to have the four side faces parallel to ( 100) planes. The crystals were electropolished8 in 10 pct H2So4 using a current density of about 3 amp per sq cm to remove the strained surface material. The crystals were bent slowly by three-point loading in a stainless-steel jig designed by Sylwestrowicz.9 The end rollers of the jig were 3.8 cm apart. DEFORMATION AT 298°K The bent vanadium crystal, after removal from the jig, had a radius of curvature of 20.4 cm over the 2-cm length close to the center loading roller, where the maximum bending moment occurred. This radius of curvature corresponded to a maximum fiber strain of 0.9 pet. The side faces contained slip bands as shown in Fig. 1. These bands are straight where the strain is high, top and bottom of micrograph, but are curved on either side of the neutral axis in the center. This curvature of the slip bands in the low-stress area may be due to cross slip. The plastically deformed crystal was subsequently electropolished and then electroetched in 10 pct H2SO4 solution, using a current density of 0.25 amp per sq cm. The structure is shown in Fig. 2. The directions of the traces on two adjoining faces were plotted stereo graphically, Fig. 3.* Since there were two sets of

Jan 1, 1968

By W. C. Hagel, H. J. Beattie

Variations in the secondary phase reactions of six nickel-and cobalt-base alloys were determined as a function of solu-tioning from 1700" to 2200°F and aging at 1200" to 1800° F for times up to 1000 hr. Room-temperature impact energies and hardnesses were also measured. Precipitation hardening of these alloys results mainly from the grain-interior formation of ? &apos;; M23C6 appears principally as grazn-boundary cells which can be eliminated by intermediate high-temperature aging treatments. Cellular precipitation of ?&apos; occurs up to 1500°F in cobalt-nickel alloys devoid of chromium, where precipitation by this mode can be attributed to a large degree of lattice disvegistery. THE usefulness of nickel- and cobalt-base alloys is dependent on balancing the strength and ductility provided by the solid-solution matrix, dislocation-type subboundaries, grain-boundary phases and genera1 precipitation within individual grains. Since equilibrium relationships for complex austenitic alloys are not easily fixed, a satisfactory balance

Jan 1, 1960