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By Robert D. Pehlke, Arden L. Bement

A mass transfer coefficient for the removal of hydrogen from liquid aluminum by inert flush degassing has been determined experimentally at 700°C. A mathematical model has been derived, assuming transport control, which adequately describes the experimental data. The removal of hydrogen is shown to increase with decreasing bubble size, and with increasing flow of flushing gas. The presence of hydrogen in liquid metals in amounts which exceed the solid solubility at one atmosphere hydrogen pressure is highly undesirable, causing unsound ingots or castings, or resulting in difficulties during further fabrication. The removal of hydrogen from liquid metals can be accomplished by several methods, the principal two being vacuum treating and inert flush degassing. The design of a process involving either of these techniques is based on the mass transfer coefficient for hydrogen between the liquid metal and a hydrogen-dilute gas phase. In an effort to extend our knowledge in this area, an investigation of the rate of removal of hydrogen from liquid metals by inert gas flushing was undertaken. In view of the difficulties encountered with gas porosity in the casting of aluminum and aluminum alloys, and because of certain experimental advantages, liquid aluminum was selected for the study. PREVIOUS INVESTIGATIONS The removal of gases from liquid metals, particularly steel, has received considerable attention in recent years, The first definitive work of a theoretical nature was presented by Geller1 who considered the case where equilibrium exists between purging gases and metal bath during flushing, and also deviations from this ideal case. Hulme2 has surveyed a number of experimental studies and discussed some of the practical limitations of removing dissolved gases from molten metals. More recently a number of studies have been reported on degassing of steel melts by flushing with an inert gas.3'4 Considerable work has also been reported on aqueous and organic liquid-gas systems, and an excellent summary prepared by Hovis.5 The treatment of liquid aluminum by a flushing gas to remove dissolved hydrogen has been known for several decades.6 A number of gases have been used for this purpose, including nitrogen, argon, and chlorine, or mixtures of these gases. Tikkanen and Erkko7 have studied the relative density changes of aluminum castings poured from melts degassed with chlorine, nitrogen, and mixtures of the two gases. Their

Jan 1, 1962

By William E. Ford, Edward Salisbury Dana

1. Normal Class (6) Zircon Type 2. Hemimorphic Class (7) Iodusuccinimide Type 3. Pyramidal Class (8) Scheelite Type 4. Pyramidal- Hemimorphic Class (9) Wulfenite Type 5. Sphenoidal Class (10) Chalcopyrite Type 6. Trapezohedral Class (11) Nickel Sulphate Type 7. Tetartohedral Class (12) Mathematical Relations to the Tetragonal System THE TETRAGONAL SYSTEM includes all the forms which are referred to three axes at right angles to each other of which the two horizontal axes are equal to each other in length and interchangeable and the third, the vertical axis, is either shorter or longer. The horizontal axes are designated by the letter a; the vertical axis by c (see Fig. 166). The length of the vertical axis expresses properly the axial ratio of a : c, a being uniformly taken as equal to unity. The axes are orientated and their opposite ends designated by plus and minus signs exactly as in the case of the Isometric System. Seven classes are embraced in this system. Of these the normal class is common and important among minerals; two others have several representatives, and another a single one only. It may be noted that in four of the classes the vertical axis is an axis of tetragonal symmetry; in the remaining three it is an axis of binary symmetry only.

Jan 1, 1922

By M. Duclos, A. Sawatzky

A simple model has been developed which describes the steady-state solute distribution in Ti-H type systems above the eutectoid temperature in the presence of a temperature gradient. The solute distribution is dependent on the shape of the phase boundaries. An interesting result, and one that is not observed at steady state in thermal diffusion below the eutectoid temperature, is the existence of a two-phase region. The heat of transport for hydrogen in a titanium, Q*a, over the temperature range 275" to 650.C is determined to be 4500 * 230 cal per mole. The heat of transport for hydrogen in B titanium, QB* over the temperature range 320" to 590.C is found to be 630 ± 200 cal per mole. It is also shown that thermal diffusion provides a method by which phase bounduries above the eutectoid may be determined in Ti-H type systems. IN modern technology materials are being used at constantly increasing temperatures under greater temperature gradients. Thus atomic migration in metal alloys due to a temperature gradient (thermal diffusion) may in some cases occur to an observable extent. The thermal diffusion of hydrogen in zirconium has in recent years received considerable attention1-' because of the use of zirconium alloys in nuclear power reactors. The thermal diffusion kinetics below the eutectoid (547°C) are fairly well understood. At steady state the solid solution, a, and hydride, 6, phases are completely separated with the hydride precipitating at the lower temperatures. No experimental work has been carried out in the a + B region although Droege4 suggested that a complete separation of the two phases, as observed at temperatures below the eutectoid, might not always occur. In the present investigation a simple model has been used to determine the steady-state solute distribution under a temperature gradient in Zr-H type systems heated above the eutectoid temperature. The solute distribution is shown to be dependent on the shape of the phase boundaries in the constitutional diagrams and several typical cases are discussed. The model has been applied to Ti-H. This system was chosen in preference to Zr-H because of its much lower eutectoid temperature (-300°C as compared with 547.C), thereby reducing experimental errors due to oxidation and hydriding. The heats of transport for hydrogen in the a and B phases of titanium also have been determined since they were required to compare the proposed thermal diffusion model with experiment. THEORY In the presence of a temperature gradient the atomic flux in a single-phase region of a two-com-ponent system of which the atoms of only one component are diffusing is given by:' J = - U\dx + RT3 dx) which can be written as: j-D(dn/dt +Q*n/RT2)dt/dx [11 J - -D\dT + RT2)dx [1] where D = diffusion coefficient, n = solute concentration, T = absolute temperature, R = gas constant, dT/dx = temperature gradient, and Q* = heat of transport. At steady state (J = 0) Eq. [I] leads to the solute distribution: n = noexp Q*/RT where no = a constant depending on total solute content. The heat of transport Q* can be experimentally determined from the steady-state distribution. In the present paper we shall determine the solute distribution in systems having the constitutional diagram exemplified by Ti-H shown in Fig. l.' As shown, N,(T) and NB(T) are the equilibrium solute concentrations in the a and 0 phases at temperature T. Lines AA' and CC' define the region of interest to us. The following assumptions are made: 1) Steady-state conditions prevail. 2) In a single-phase region all points on an isotherm have the same thermodynamic potential so that the composition over an isotherm is uniform. If a two-phase region exists, thermodynamic equilibrium is found only at phase interfaces. However, we assume the component of the concentration gradient along an isotherm to be small so that the composition in each phase is approximately the same as at the interface and is given by the constitutional diagram, Fig. 1. 3) There is appreciable diffusion of only one component. 4) We shall consider only the case where Qa*, QB*, and Qg*, the heats of transport for solute diffusion in the a, B, and 6 phases, respectively, are positive. This has been observed for the thermal diffusion of hydrogen in zirconium3 and titanium.10 We will show that the steady-state solute distribution above the eutectoid is primarily determined by the heats of transport and the temperature dependence of Na(T) and Np(T). It may be quite different from the steady-state distribution below the eutectoid. For example, we will see that, under certain conditions,

Jan 1, 1970

By D. P. Kedzie, R. A. Dodd

The fatigue strength, fatigue hardening, and effect of fatigue deformation on subsequent age hardening of supersaturated Al(Cu) solid solutions have been determined as functions of alloy composition and temperature. The fatigue strength/tensile strength ratios, determined at 150°, 25°, and -195°C, decreased with increase in alloy content for all temperatures, but the F.S./U.T.S. ratios at -195°C decreased much more rapidly than did the ratios for 150" and 25°C. This suggested that strain aging and/or age hardening occurred during tests at higher temperatures. Additionally, the F.S./U.T.S. ratios at 150°C exceeded those at 25°C for all compositions, indicating greater strengthening during fatigue at 150°C. The effect of fatigue or tensile deformation at 150°, 25°, and -195°C on subsequent age hardening showed that the deformatzon increased the rate of precipitation and indicated that mechanically produced vacancies were probably formed during deformation. Fatigue hardening was studied at 150°, 25°, and -195°C, and the effect of room-temperature rests after 10 and 100 cycles was examined. The results confirmed that strain aging occurred at the higher temperatures . DURING the last 15 years various mechanisms of fatigue crack nucleation and growth based on dislocation and vacancy interactions, operating singly or collectively, have been proposed. The probable consensus of present opinion is that the fatigue process in pure metals essentially involves dislocation interactions, and that vacancies formed by such interactions play a minor or inconsequential role. However, there is some evidence that age-hardened alloys tend to overage during fatigue, probably by local vacancy-enhanced diffusion, and strain aging also might be important in selected cases. Furthermore, it has been established that the behavior of quenched-in vacancies in Al(Cu) and other solid solutions is composition-sensitive. Therefore, it seemed worthwhile to investigate various aspects of the fatigue behavior of supersaturated Al(Cu) alloys and to examine the results in terms of vacancy-enhanced effects. EXPERIMENTAL The alloys used in this investigation were prepared from 99.994 wt pet A1 and OFHC copper, the latter containing 0.04 pet 0 as the principal impurity. Six alloys were made, containing, by actual analysis, 0.58, 0.96, 1.96, 2.85, 4.45, and 5.51 wt pet Cu. They were induction-melted in air in graphite crucibles, cast as 7-in. by 7/8-in.-diam rods in graphite molds, and hot-rolled to 5/8 in. diam. The experimental work was a three-part program involving the determination of a) 10' cycle fatigue stresses as a function of alloy composition and temperature; b) the effect of fatigue deformation on subsequent aging of the supersaturated alloys; and c) fatigue hardening as a function of alloy composition and temperature. For determining the 105 cycle fatigue stresses, a portion of the 5/8-in. stock was machined into Krouse rotating cantilever beam fatigue specimens, 2 in. in length by 1/4 in. minimum diameter. These were tested at +150°, 25°, and -195°C (liquid nitrogen) on a Krouse high-speed machine, with special weights to provide lower -than-normal loading ranges, this being necessitated by the small load requirements of those alloys of lower copper content. For the high-temperature tests a small resistance heater was designed to clear the collets and fit in between the chucks, while for the low-temperature tests a hollow nylon cylinder was used, having closed ends drilled to pass a fatigue specimen, and positioned similarly to the heater. A plexiglass container completely enclosed the fatigue machine; rubber gloves fixed to ports in the walls enabled the machine to be operated from outside the box. A tray of magnesium perchlorate dried the air in the container and prevented both atmospheric corrosion fatigue at room and elevated temperatures and troublesome ice build-up at low temperatures. A total of ten to fifteen specimens was used for each combination of alloy composition and temperature. The result of each test was plotted on a standard S-N diagram, and the next stress was selected on the basis of the trends indicated by previous specimens. In this manner a small portion of the S-N diagram was constructed, and the 105 cycle fatigue stress obtained. Small Krouse fatigue specimens were also used to study the effect of cyclic prestrain on subsequent

Jan 1, 1964

By J. P. Carson

THE Croton water-shed furnishes the source and storage of watersupply to both the old and the new aqueduct. The Croton river rises in the southern part of Dutchess county, about 68 miles from the lower end of New York city. Its three main branches, called the East, Middle and West branches, flow southward across Putnam county, joining, near its southern boundary, to form the Croton, which continues thence in a general southwest direction across Westchester county to the Hudson river at Croton Point, about 35 miles north of the city. The water-shed above the proposed site of the Quaker Bridge dam extends about 33 miles north and south, with an average width of 11 miles, making in all about 362 square miles, from which, by complete storage, an average daily supply of 250,000,000 gallons may be collected—sufficient for the needs of the city, probably, for the next fifteen years. The water-shed above the Croton dam is 23 square miles smaller, and furnishes the present daily supply of 100,000,000 gallons. By referring to the map it will be seen that the shortest approximately straight line between the proposed site of Quaker Bridge

Jan 1, 1891

Jan 1, 1951

By A. J. Hendron, D. U. Deere, F. D. Patton, E. J. Cording

In the design of structures founded in the near-surface rock, a distinction may be made between those problems that are related to the strength of the rock mass, and those that are related primarily to the compressibility of the rock mass. The mining engineer deals almost exclusively with problems involving strength in the design of open-pit slopes and underground openings. The civil engineer is similarly concerned with strength problems in the design of vehicular and water tunnels; underground power plants; cut slopes in rock for highways, canals, and spillways; and in the study of the sliding resistance of the foundations of gravity dams and the abutments of arch dams. Moreover, the civil engineer encounters problems in which the compressibility of the rock becomes the key element in the design. These problems include settlement of heavy structures supported on rock, deformation of the abutments of arch dams, and deflection of pressure tunnel linings. The design problems listed above are still solved largely on the basis of experience and rule-of-thumb. However, recent developments in rock mechanics give promise of providing more realistic approaches to certain aspects of the design. This paper, presents some of the more important recent developments which contribute to an understanding of rock behavior and which aid in design of rock structures. Typically, four steps are involved in the design of a structure, whether it be a machine element, a structural member of a building, or a structure in rock. These steps are listed below:

Jan 1, 1967

By George E. Thackray

In December, 1894, the Cambria Iron Company made a number of heats of Bessemer steel to be used in structures by one of its customers, subject to inspection and tests by a firm of consulting engineers, one of the requirements being that the material should riot exceed .08 per cent. of phosphorus. In other respects the requirements were such that they could only be met by material of good quality; but the general spe cification is not introduced here, as it is not the purpose of this paper to deal with anything except certain difficulties encoun tered in determining the phosphorus-content of the material in a manner satisfactory to both seller and buyer. Preliminary determinations of phosphorus were made in sample-ingots from each of the heats from which material was rolled for the order in question, and these preliminary chemical tests, made in the laboratory of the Cambria Iron Company, showed that, with very few exceptions, every heat was within the prescribed limit of phosphorus. After the material had been rolled, sample-drilling8 of finished material were taken from the various heats in the regular manner in use at the works, these samples being thoroughly mixed and divided into two parts, one of which was analyzed at the works' laboratory and the other sent to the inspecting engineer. Several hundred determinations were made from this mate rial without reaching an agreement between the work of the inspector's chemist and that of the works' chemist; but as it is not the object of this memorandum to treat of this part of the subject at length, it is considered sufficient to present herewith only a few of these first determinations. The analyses given in Table I. are those of the original series made on the heats which were afterwards resampled for final determination by an arbitrator; and they are selected for this reason, as the entire " comparison is thus rendered more complete.

Jan 1, 1896

By H. Hubert

The first attempts at direct utilization of blast-furnace gas in engines were made in 1895. For a considerable time the gas had been burnt in Cowper stoves for heating the blast for the furnace, and under the boilers which supplied steam to the blowing-engines, and others serving the furnaces. It was natural, therefore, that the idea of directly employing it in gas-engines should have occurred simultaneously to several engineers, notably to Lurmann and to Lencauchez, who had pointed out the blast-furnace as a powerful gas-producer. Nevertheless, nowhere had any attempt been made to apply it to this purpose up to the end of 1894, when Thwaite proposed it to Mr. James Riley, of the Glasgom Iron & Steel Company. About the same time investigations were being made in Belgium and in Germany, independently of Thwaite's experiments, which were not generally known on the Continent. The industrial world, which up to that time had hardly favored the idea, had thus been gradually prepared to receive it. The gas-engine, long restricted to small sizes and dependent upon the use of an expensive fuel obtainable only in large centers, now began to make headway. At the Paris Exhibition of 1889 two engines of 100 h.p. were shown and excited much interest among engineers. One had four cylinders, and was made at the celebrated works of the Deutz Company, and the other was a single-cylinder engine, exhibited by two French designers, Messrs. Delamare-Deboutteville and Malandin. In the meanwhile the design of gas-producers had made important progress, completely freeing the new engine from its

Jan 1, 1907

By B. E. Mix

THE present methods of unloading ore and coarse-crushing at the Magna plant of the Utah Copper Co. are the developments of the past five years. Hand dumping and breaking have given way to the rotary car dump and large gyratory; and the bucket elevators and stationary screens have been replaced by conveyors and shaking screens. The coarse-crushing plant may be broadly divided into two units: the primary crushing and the secondary crushing, or primary roll, unit. The former was erected in 1923; with the exception of the excavation, the construction was carried on by forces of the company. Excavation was started in the middle of March, the first concrete was poured July 16, erection of the steel building started Oct. 30, and the unit was com-pleted and operating Dec. 30. The unit has a capacity of over 24,000 tons of ore per day, and cost more than a million dollars. Remodeling of the primary-roll unit extended over a period of years preceding this, some of the work having been done as early as 1918.

Jan 8, 1925

By R. S. Shoemaker, F. W. McQuiston

EMPEROR GOLD MINES Vatukoula, Fiji 1974 Operating Data to July 1 ORE DESCRIPTION: Ore bodies occur in basalt and associated ash beds overlain by andesite tuffs and sediments. The basalt in much of the ore mined is weathered with alteration of olivine to serpentine and iron oxides, and augite to chorite. The most important host minerals for gold are the tellurides sylvanite and hessite. Next in importance the sulphide s, pyrite, marcasite and arseno-pyrite. A small amount of free gold also occurs. Chalcopyrite, sphalerite, tetrahedrite, bornite, galena and native tellurium are present in small quantities. TYPE OF MINE: Underground and open pit ORE HAULAGE TO MILL: 3.5 ton bottom dump skips from underground. 7 ton trucks from open pit. CAPACITY IN TONS/24 HRS: 1345 short tons ASSAY HEADS (1973): 0.232 oz Au per ton, 0.357 oz Te per ton PRODUCTS: Gold Bullion (400 oz bars) Metallic Tellurium (1 2 lb bars ) RECOVERIES: AU 86.2% Te 88.0% ORE GRINDABILITY: 9.25 Kwh/T TOTAL POWER: 25.7 Kwh/T WATER: Pumped 112 mile to a 318, 000 gallon head tank. Consumption: 2 140 gal per ton, no reclaimed water used. TAILINGS: Pumped 2 /3 mile through 8" pipe. Uphill sections are steel. Downhill sections are fibro asbestos.

Jan 1, 1975

By C. W. Pollock

THAT a distressing explosion of some magnitude did not take place in the Berry No. 3 mine of the Ford Collieries Co. recently was solely because no source of ignition was present when the stage was set for such an occurrence. The mines of this company, which are in West Deer Township, Allegheny' County, Pa., have been operating in the double or thick Freeport seam since 1.909. During this entire period they have been classed as gaseous by the Pennsylvania Department of Mines, and some gas has been encountered from time to time almost entirely however in development work in the vicinity of clay veins or wants-and never to my knowledge on gobs or in rib work.

Jan 1, 1935

By E. M. Wise, T. E. Kihlgren, N. B. Pilling

SYSTEMATIC data are presented on the relation of composition of nickel silvers to color, tarnish resistance, hardness and liquidus temperatures, for alloys containing up to 30 per cent nickel and 50 per cent zinc, further modified at certain nickel and zinc contents by 0 to 8 per cent of tin and 0 to 10 per cent of lead. Attention has also been directed, using a still more limited range of alloys, toward a study of tensile properties and such casting properties and characteristics as fluidity, shrinkage and pressure tightness. In some of these, rather broad ranges of composition are dealt with; in others, it has been expedient to focus attention on the Federal Specification 20 per cent nickel silver casting alloy, WWP-541.

Jan 1, 1935

By Arne F. Westgren

X-ray analysis and single-crystal study have been utilized in recent years as a new means of following constitutional changes in alloys. If such transformations can be suppressed by rapid cooling, they can be followed at room temperature in a particularly convenient manner. In the following we shall consider changes in solubility and polymorphic transformations with particular reference to phenomena of the age-hardening type. Finally a thermodynamic viewpoint is developed for examining such transformations. Changes in Solubility 1. Determinations of solubility limits in the solid state which show decreasing solubility with falling temperature are made as follows: A series of alloys extending into the heterogeneous region is prepared and quenched fromas high a temperature as possible, whereupon their lattice parameters are determined. Then one or more alloys are quenched from temperatures at which they are heterogeneous and their lattice parameters likwwise determined. For the purpose of determining the parameter the apparatus shown in Fig. 1 has been very useful for it produces sharp films in a short time which can be accurately read. High-order reflections (interferences) from the object are recorded on a film which is placed exactly perpendicular to the X-ray beam. The specimen usually has the shape of a small round bar.l Fig. 2 shows a selection of such exposures of silver-rich Cu-Ag alloys, and Fig. 3 gives the measurements made from these films. Fig. 4 gives the solubility curve which results.2 This curve is shifted to lower concentrations than the curve that is obtained from metallographic or physical methods. The X-ray method unquestionably gives more reliable data

Jan 1, 1931

By C. Graeme-Barber, R. L. Bell, T. G. Langdon

An analysis is made of the formulas and ,methods used to estimate the contribution of grain boundary sliding to the overall strain of a polycrystal. The errors involved in the approximations and/or ,mistakes in earlier work are assessed quantitatively so as to make possible the critical use of previously published data. SINCE it has been found that, under conditions of very slow creep, the strain due to grain boundary sliding (?gb) may contribute as much as 80 pct of the total creep strain,1,2 it is obviously important to have reliable methods for estimating this grain boundary strain. In two recent papers Stevens3,4 has drawn attention to the pitfalls encountered in assessing ?gb. He criticizes 1) the assumptions made in the derivation of some of the formulas for ?gb, and 2) the indiscriminate averaging procedures used for obtaining the quantities substituted in these formulas. These and further criticisms of earlier work are mostly valid. Unfortunately the only formulas and procedures recommended are either impossible or very difficult to apply in practice. Furthermore no attempt is made to assess the errors involved by the earlier approximations or mistakes, and so it is not possible to make critical use of any of these early dab. The present article attempts to improve on these shortcomings by reference to empirical verification of easily applied formulas whose theoretical derivations involve some otherwise unjustifiable assumptions, and by a quantitative assessment of the errors in previous work. DEFINITIONS First it is necessary to define the terms and symbols to be used. The choice of symbols preferred here is a logical combination and extension of the v introduced by McLean5 and the u by Brunner and rant.' In Fig. 1 the two grains X and Y are displaced by the sliding vector AC. u is the component of sliding resolved along the stress axis, v is that measured perpendicular both to the stress axis and to the specimen surface, and w is that measured perpendicular to the stress axis but in the plane of the surface. Two angles define the orientation of the grain boundary: 8, between the stress axis and the surface trace of the boundary, and +, the internal angle on a longitudinal section cut perpendicular to the surface. In computing the strain resulting from the boundary displacement at all the in- dividual boundaries in a polycrystal the components u, v, or w are sometimes averaged along a longitudinal line (i.e., parallel to the stress axis), sometimes along a transverse line, and sometimes at randomly chosen boundaries. Averages obtained in these three ways are given subscripts 1, t, and r, respectively. Stevens rightly calls attention to the possibility of non-equiaxed grain shapes either at the start or at the end of deformation. In this article all values of numbers of grains per unit length will refer to measurements made before deformation. The subscripts 1 and t will be used for the number of grains per unit length obtained along longitudinal and transverse lines, r for that obtained by averaging along a number of randomly directed lines. FORMULAS FOR ?gb ?gt, as a Function of u. An obvious truth is that cgb can, in principle, be obtained by summation of all the v components at the boundaries intersected by a longitudinal line of known length I, viz.: where nl is the number of grains per unit length, parallel to the stress axis, in the unstrained specimen. There are assumptions in the analytic derivation of Eq. [I] due to Brunner and rant' but ~achinger' arrived at Eq. [la] by a rigorous method. Unfortunately the experimental procedure required by Eq. [ la] proves very difficult as boundary migration tends to obscure the points at which the longitudinal line meets the grain boundary and the errors on such measurements tend to be large, see Fig. 2. For example, on a specimen of Magnox AL 80 at a creep strain of 9.7 pct, 300 measurements of u obtained from the points of intersection of a longitudinal line with the grain boundaries gave ul = 8.95 ± 3.58 pm, or an error of ±40 pct, at the 95 pct confidence limit. These large errors due to migration may be avoided by measuring u from the separation of the segments

Jan 1, 1968

By Charles S. Barrett

THE experiments reported in this paper have been fruitful in disclosing the mechanism of the deformation of iron in compression. They have established the nature of "deformation bands," "etch bands," or "X-bands," that have been a recognized but little understood feature in the structure of cold-worked metals since the early days of metallography, and have shown the role of the bands in the development of preferred orientations by cold-working. The work has also shown the relation of the orientation of individual grains to the preferred orientation of the aggregate. Some of the methods previously used in the determination of the indices of slip planes and slip directions are shown to be untrustworthy in the presence of deformation bands. The conclusion is reached that many slip planes and slip directions must operate during each stage in the compression of a single crystal, and that theories failing to take account of this require revision. In conducting the experiments a method of compression has been used by which extreme reductions can easily be reached, even to the limit set by the metal's capacity to deform without fracture. The work is a portion of a research program on the plastic properties of iron and steel. It is being used as a foundation for studies of orientations resulting from recrystallization and is being extended to other metals and other types of deformation. PREVIOUS WORK The previous experiments are few and have given confusing results. Ono1 compressed a polycrystalline alpha-iron specimen between two flat plates of a testing machine and found that severe deformation oriented the crystals into a duplex preferred orientation, one set of crystallites having a cube diagonal of the body-centered cubic lattice parallel to the compression axis, and another set having a cube axis parallel to the compression axis. We shall speak of this structure as a. double fiber texture of the type [111] + [100]. Wever2 also made an X-ray determination of the texture

Jan 1, 1938

By J. F. Olk, E. D. Spaulding, R. E. Thurmond, G. A. Komadina, R. W. Hernlund, J. A. Journeay

THE Pima pit is a 1700x1400-St oval, the long T axis parallel to the strike of the orebody. The north side of the pit is carried as a final pit slope that coincides with the footwall of the orebody. The south side and east and west ends of the pit are working slopes continually being stripped back toward the final slopes. An inclined roadway extending from the natural ground surface on a 5 pct grade down to the north- east corner provides access to the pit. This road enters the pit 130 ft below the natural surface and continues as a pit ramp on a 5 pct grade to the 3150-ft bench (roughly the base of the alluvial cover). At this point the ramp system is steepened to a 12 pct grade and continues to the pit bottom. The 5 pct grade is maintained in the alluvial section to facilitate scraper haulage out of the pit. In addition to this main access ramp, temporary working ramps in the alluvial areas allow shorter routes to dumps. These are left on top of working benches and do not change the overall working slopes. Below the base of the alluvium, haulage is by truck down to the skip loading point or up from the bottom to the skip loading point.

Jan 4, 1958

By J. P. Murphy, T. E. Leontis

DURING the last few years, the trend in the aircraft and automotive industries has been toward higher and higher operating engine temperatures. This has created considerable interest in the effect of temperature on the properties of alloys. In the magnesium field, it has been recognized for many years that the addition of cerium imparts high strength and good resistance to creep at elevated temperatures. Beck,1 in his treatise on-magnesium, has summarized the work of German investigators. This includes the unpublished data of Menking, showing the increase in strength and hardness of extruded alloys containing 2 to 20 per cent Ce at temperatures from 200 to 300°C. (68° to 572°F.) and the results of Vosskühler, who demonstrated the improved resistance to creep of alloys containing 6 per cent Ce plus 2 per cent Mn and 0.5 per cent Ce plus 2 per cent Mn at 150°C. (302°F.). Wellinger and Keil2 have also reported the creep properties of a forged magnesium-cerium-manganese alloy at 200° and 250°C. (392° and 482°F.). Haughton and Prytherch have determined the tensile properties of various forged magnesium alloys containing cerium, cerium plus manganese, cerium plus calcium, cerium plus nickel, cerium plus nickel plus manganese, and cerium plus cobalt plus manganese at temperatures up to 290°C. (554°F.). Magnesium-cerium alloys have been used in some commercial applications. It is reported that an alloy containing 3 per cent Ce plus 0.5 per cent Mn plus 0.5 per cent Ca is being used on a forged impeller in Great Britain. Two forged parts made from an alloy with a nominal composition of 5 per cent Ce and 2 percent Mn have been found on the German .BMW-801D aircraft engine. These two forgings consist of a supercharger impeller and a rear cam-follower guide. In this country, several types of pistons have been made experimentally in both .the cast and the forged conditions from an alloy containing 6 per cent Ce plus 2 per, cent Mn and in the cast condition from an alloy of magnesium plus 10 per cent Ce. The cast pistons have been tested in various types of internal-combustion engines, with promising results. This paper presents the results of an extensive investigation on the properties of various cerium-containing magnesium alloys in both the cast and the forged conditions. Data are presented to show the beneficial effects of increasing amounts of cerium on the mechanical properties of magnesium at elevated temperatures. The effects of heat-treatment on the properties of these alloys and the attendant changes in the microstructure are discussed. The

Jan 1, 1946

By M. L. Holzworth, Philip R. Sperry, Paul A. Beck

INTRODUCTION THE basic work of Z. Jeffries1,2,3 has long ago established the main features of grain growth in the presence of a dispersed second phase. Working with sintered specimens of initially fine grained tungsten, to which various amounts of thoria have been added, Jeffries found that grain growth was inhabited, that is, practically prevented, up to a certain annealing temperature. When this temperature, which increased with the thoria content, was exceeded, extremely large grains developed abruptly from the fine grained matrix. Such a "coarsening temperature" was later found by Gross mann13,14 in certain types of steel, while Bain showed" that in other steels grain growth was gradual, without inhibition and abrupt coarsening. Later work16,17,18,19,21 demonstrated the connection between coarsening and aluminum additions. The viewpoint that the direct cause of inhibition and coarsening in aluminum killed steels is a fine dispersion of aluminum oxide21 appears to be held quite generally, although some doubts have been voiced even very recently.20 In steels with Ti additions the titanium carbide phase is considered responsible for the inhibition effects found.20 The coarsening temperature increases, with the titanium content. That coarsening may occur, as a result of certain heat treatments, even in low carbon rimmed sheet steel, was shown by Samuels,22 He also detected coarsening in a steel ingot of similar composition, after giving it the same heat treatment as that used by him for the sheet material, In this instance the identity of the inhibiting phase has not been determined, However, Tangerding found 23 that even the few small carbide particles, which occur in carbonyl iron, have a very marked inhibitive effect. As a result of an oxidizing anneal at 850°C, large grains begin to form at the surface of the carbonyl iron specimen, and gradually grow inward as the subsurface oxidation of the carbide particles progresses and eliminates the obstruction, The carbide particles can be removed also by annealing in hydrogen, with similar results. But if the oxidizing anneal of 10 hr at 850°C in air, is followed by annealing in hydrogen for 75 hr at the same temperature, grain growth is more spectacular; usually the whole specimen is transformed into a single crystal (approx. 1,5 cm X 5 cm). The reversed procedure, that is, hydrogen annealing followed by oxidizing annealing leads to smaller grains. Tangerding arrived at the logical conclusion that there must have been in his specimens some additional obstruction to grain growth resulting from a minor impurity, other than carbon. It seems likely that this obstruction was caused by an oxide formed during the oxidizing anneal and gradually reduced during the subsequent hydrogen-annealing. Other instances of grain growth inhibition of varying severity, associated with a dispersed second phase, have been described by several authors. Notable examples: lead with 0.06 pct Cu or Ni,24 cartridge brass with 0.12 pct Cr,25 or with up to 0.15

Jan 1, 1948

By J. Chupak, D. J. Salley, G. L. Simard

Radiotracers were demonstrated to be of considerable value in a study of the interaction of dithiophosphate with galena. The interaction had characteristics of both chemisorption and chemical reaction, being complex because of the nature of the galena surface. Sorption was rapid and markedly reversible, and flotation occurred at relatively small amounts of dithiophosphate sorbed.

Jan 1, 1950