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Trans No. Place Date Vol. 1. Wilkes-Barre, Pa. May, '71 1 2. Bethlehem, Pa. Aug., '71 1 3. Troy, N. Nov., '71 1 4. Philadelphia, Pa. Feb., '72.. 1 5. New York, N. Y. May, '72 1 6. Pittsburgh, Pa. Oct., '72 1 7. Boston, Mass. Feb., '73 1 8. Philadelphia, Pa. May, '73 2 9. Easton, Pa. Oct., '73 2 10. New York N. Y. Feb., '74 2 11. St. Louis, Mo. May, '74 3 12. Hazleton, Pa. Oct., '74.. 3 13. New Haven, Conn. Feb., '75 3 14. Dover, N. J. May, '75 4 15. Cleveland, Ohio Oct., '75 4 16. Washington, D. C. Feb., '76 4 17. Philadelphia, Pa. June, '76 5 18. Philadelphia, Pa. Oct., '76 5

Jan 1, 1941

Trans No. Place Date Vol. 1. Wilkes-Barre, Pa. May, '71 1 2. Bethlehem, Pa. Aug., '71 1 3. Troy, N. Nov., '71 1 4. Philadelphia, Pa. Feb., '72.. 1 5. New York, N. Y. May, '72 1 6. Pittsburgh, Pa. Oct., '72 1 7. Boston, Mass. Feb., '73 1 8. Philadelphia, Pa. May, '73 2 9. Easton, Pa. Oct., '73 2 10. New York N. Y. Feb., '74 2 11. St. Louis, Mo. May, '74 3 12. Hazleton, Pa. Oct., '74.. 3 13. New Haven, Conn. Feb., '75 3 14. Dover, N. J. May, '75 4 15. Cleveland, Ohio Oct., '75 4 16. Washington, D. C. Feb., '76 4 17. Philadelphia, Pa. June, '76 5 18. Philadelphia, Pa. Oct., '76 5

Jan 1, 1934

By F. C. Bond

Since the Third Theory of Comminution was presented eight years ago (I) it has found increasing use in crushing and grinding problems. The practical utility of its wok index equation is quite generally acknowledged (2). However, its theoretical basis has been questioned in at least three technical articles (3) (4) ('). The purpose of this paper is to present experimental proof that it is scientifically correct. Particles under compressive stress are strained and deformed. They absorb strain energy, and when this locally exceeds the breaking strength, a crack tip forms. The surrounding strain energy flows to the crack tip, which rapidly extends and splits the rock, releasing the strain energy as heat. The initial energy flow causes additional crack tips in highly strained areas. If the compression is rapidly applied by impact, crack tips may form before the strain energy has reached equilibrium in the particle, thus decreasing the total work input required for breakage. The energy necessary to break is essentially the energy necessary to produce crack tips, since the energy necessary to extend the cracks to breakage is already present as strain energy in the deformed particles. After breakage nearly all of this energy appears as heat. The crack length cannot be measured directly. However, in particles of regular and similar shape the crack tip length is considered as equal to the crack depth, or crack extension necessary to break, so that the crack length equals the square root of one-half of the surface area. The Third Theory states that the useful work done in crushing and grinding is directly proportional to the total length of the new cracks formed. It can be confirmed by showing that a constant work input produces a constant length of new cracks when reducing the same material to different product sizes. This is done in the present paper on a wide variety of material. The constant work input was supplied by one revolution of the 12" x 12" laboratory ball mill used in making grindability tests by the Allis-Chalmers method (12) (13) The new crack lengths produced per mill revolution were measured from all available grindability test results at 28, 35, 48, 65, and 100 mesh on fifteen different ores, and were found to remain substantially constant for each ore at all mesh sizes. A new technique is used for the measurement of crack lengths. Size distribution plots of the mill feed and product are made by the Third Theory method (9) and the crack lengths are obtained from these plots by the procedure described in the present paper. The energy input required to produce a unit length is of fundamental importance in the size reduction of brittle solids. The crack length Cr is expressed in centimeters per cubic centimeter of solid material. It bears a definite relationship to the external surface area of the crushed or ground solid. A uniform particle shape must be assumed before the surface area and crack length can be evaluated. In this paper it is assumed that the relationship between the surface area and the particle volume of a particle d microns in diameter is the same as that of cube d microns on a side. The external surface areas of particles with a cubical breakage probably agree approximately with this rule, and correction factors can be applied when physical measurements of the surface areas are available for comparison. However, the assumption of equivalent cubes has been found satisfactory for most calculation purposes. Assuming equivalent cubes, one cubic centimeter of particles d microns in diameter will have a crack length Cr of v30.000/d centimeters, and a surface area of 60,000/d square centimeters. The specific crack length is thus equal to the square root of one-half the specific surface area. Where Sa is the surface area in square centimeters per gram and Sg is the specific gravity of the ground solid, then Cr = vSg . Sa/2 = 173.2/ vd (1)

Jan 1, 1961

By R. L. Jones, H. Conrad

The effects of gain size on the room-temperature tensile properties of commercial(A- 70)-purity and iodide-purity titanium were investigated by concurrent tensile testing and thin-foil electron transmission studies. The mechanical tests showed that the effect of grain size on the yield, flow, and fracture stresses could be expressed by relations of the Hall-Petch type. The magnitude of the grain size effect on the yield stress was larger for commercial-purity than for high-purity titanium, but in both materials it was intermediate between that typically observed for fcc and for bcc metals. The effect of strain on the gain size sensitivity of the flow stress was found to reflect the grain size dependence of strain hardening. The electron transmission study indicated that the tensile behavior could be accounted for in terms of the dislocation densities and distributions formed during deformation. It was concluded that the effect of grain size on strength could be attributed to a relationship between grain size and the dislocation densities generated in initiating and sustaining plastic flow, the difference in stress levels being due to strain hardening. The relationships between recrystallized grain size, uniaxial tensile properties, and dislocation substructure have not been explored in any detail for a titanium. With titanium and its alloys finding increasing applications in aerospace systems, such information has become essential. The research described in this paper had two objectives: first, to document the effect of grain size on the yield, flow, and fracture stresses of unalloyed a titanium by the tensile testing of recrystalliied specimens at room temperature; second, to attempt an interpretation of the mechanical test behavior in terms of the dislocation structures formed on deformation, as observed by transmission electron microscopy of thin foils prepared from deformed tensile specimens. The observations reported here are restricted to room-temperature deformation; the effect of temperature on the yield and flow stresses of a titanium and the athermal nature of the contribution of grain size to the flow stress have been discussed elsewhere.1"3 EXPERIMENTAL DETAILS Two purity grades of unalloyed titanium have been investigated: Crucible Steel A-70, a typical commer- cial-purity product, and a high-purity iodide grade supplied by the Foote Mineral Co. Chemical analyses for interstitial impurity contents are given in Table I, together with values for the total interstitial atom fractions in terms of oxygen equivalents, which were calculated by the method outlined previously.4 ,5 According to the manufacturer's nominal analysis, the A-70 grade also contains about 3700 ppm of Fe. The A-70 grade was supplied as 1/4-in.-diam centerless-ground rod. The iodide grade was supplied as crystal bar which was consolidated to approximately 1/4-in.-diam rod by a single, rapid, molten zone pass, using electron beam heating. The 1/4-in. rods were cold-swaged to 0.078-in.-diam wires and 2-in. lengths were recrystallized in a vacuum of -5 x 10-5 torr, giving grain sizes in the range 0.8 to 30 . The thermal treatments and resulting grain sizes are summarized in Table 11. Since there was in no case any obvious sign of a bimodal dis tribution of grain sizes, the grain size values quoted in Table I1 are those obtained from mean linear intercept measurements involving >I00 grains. For the two coarse grain sizes the measurements were made using conventional optical techniques. It was noted during these determinations that the etchants used (10 pct HF; 30 pct HN03; 60 pct H20 and 2 pct HF; 2 pct H202; 96 pct H20 were both tried) etched grain boundaries very nonuniformly and optical polarization effects had to be employed to reveal boundaries which might otherwise have been missed. It was found that this problem became more acute with the finer grain sizes as the usefulness of polarization diminished.

Jan 1, 1970

Trans No. Place Date Vol. 1. Wilkes-Barre, Pa. May, '71 1 2. Bethlehem, Pa. Aug., '71 1 3. Troy, N. Nov., '71 1 4. Philadelphia, Pa. Feb., '72.. 1 5. New York, N. Y. May, '72 1 6. Pittsburgh, Pa. Oct., '72 1 7. Boston, Mass. Feb., '73 1 8. Philadelphia, Pa. May, '73 2 9. Easton, Pa. Oct., '73 2 10. New York N. Y. Feb., '74 2 11. St. Louis, Mo. May, '74 3 12. Hazleton, Pa. Oct., '74.. 3 13. New Haven, Conn. Feb., '75 3 14. Dover, N. J. May, '75 4 15. Cleveland, Ohio Oct., '75 4 16. Washington, D. C. Feb., '76 4 17. Philadelphia, Pa. June, '76 5 18. Philadelphia, Pa. Oct., '76 5

Jan 1, 1942

By Oliver M. W. Sprague

THIS gold problem is full of complications and can hardly be handled adequately or comprehensively in any short period of time. Perhaps I might begin by mentioning a few aspects of the subject about which I suppose there will be no disagreement. The first of these is that we already have a stock of monetary gold in the United States far in excess of what is needed to support any desirable increase in the present volume of currency and credit. The second is that this already superabundant gold stock is certain to be considerably enlarged during the course of the war, and presumably during the months of readjustment following its conclusion. Some billions of additional gold, we may reasonably presume, will come into the country during these next few years, thus increasing the aggregate monetary gold stock from the present eighteen billions to perhaps twenty- two or even twenty-five billion dollars.

Jan 1, 1940

By Z. F. Oszter

This paper discusses the materials handling problems encountered in cement plants in the areas of raw and finished product grinding and cement storage. It illustrates by examples taken from actual installations, how optimum feed rate is maintained in grinding circuits with properly applied bin dischargers (vibrating hoppers, Mexican feed boxes and aerated bin bottoms) for materials with high moisture content and/or difficult handling characteristics. Initial operating problems with the equipment will be discussed and maintenance requirements will be indicated for comparison purposes. In a modern cement plant, properly functioning bins and feeders are as essential as process control, for no process control system, however sophisticated, can perform efficiently if raw materials do not flow into the plant processing facilities at the required time and rate. Most materials used in the manufacture of portland cement - such as silica sand, iron ore fines, crushed limestone, gypsum, clinker or cement itself-have difficult handling characteristics under specific conditions. High moisture content or even dampness due to condensation may create bin hang-ups, arching and ratholing, all of which result in improper functioning of the feeders or proportioning equipment. The occurrence of these problems in existing cement plants spurred a search for the corrective devices discussed in this article. The equipment investigated included bin dischargers in the form of vibrating hoppers for moist raw materials, Mexican feed boxes for clinker and aerated bin bottoms for cement. Operating experience with different types of bin dischargers showed that the actual performance of some did not come up to the expected level under prevailing operating conditions. The aim of this paper is to record the results of this experience and there- by aid designers and/or operators in selecting the most suitable equipment for their requirements. BIN DISCHARGERS (GENERAL) A discharger is a device that causes stored solids to flow out of a hopper without metering the rate of flow as a feeder does. The investigation discussed here encompasses the following types of bin dischargers used in a cement plant: (1) vibrating hoppers (horizontal motion), (2) whirlpool hoppers (horizontal and vertical motion), (3) aerated bin bottoms (air fluidization), and (4) Mexican feed boxes. Most of the bins used in the cement industry are of the plug flow type. Raw materials with difficult handling characteristics such as high moisture content may cause flow problems when fed through small openings (12 x 18 in.), even if two walls of the bin are vertical.' The most appropriate solution to these flow problems would be the installation of separate mass flow bins for the different materials such as silica sand, iron ore fines, crushed limestone and gypsum, with each bin correctly designed from test data obtained by measuring the flow properties of representative samples. However, limited storage capacity and plant space usually preclude this approach. Quantitative design of bins for flow based on measured flow properties of representative samples of the bulk solid to be handled is no longer an "engineering art," thanks to the basic research done on the flow of bulk solids in bins during the last decade.2, Where space limitations exist, however, or where improvements are being sought for equipment already installed, bin dischargers offer a satisfactory solution to flow problems. They can be applied effectively under flat-bottom bins or mounted to existing plug-flow bins with very little modification to these facilities. In both the foregoing cases, plug flow will be maintained, but the flow channel will be considerably increased so that it is larger than the discharger's bin-side diameter, and material flow can be sustained if the discharger is correctly selected. The main purpose of a bin discharger is to draw the bulk solids across the whole area of the bin outlet, to make the opening fully effective. As long as the bin-side opening of the discharger is large enough

Jan 1, 1969

By Morris Cohen, Robert C. Ruhl

Fe-Ni-B alloys were inresligated by X-ray diffraclion after splat quenching. Although this rapid cooling did not produce a measurable supersaturation of dissol1ed boron in either binary Fe-B or Ni-B alloys, a marked increase in dissolved boron was achieved by the splal quenching of lernary Fe-Ni-B alloys. Boron additions up to 2.0 wl pcl to Fe-13Ni and Fe-24Ni alloys cause an increase in retained austenite from 0 to 59 pet and to 92 pet, respectively. The martensitic phase in the Fe-13Ni-9 at. pct B alloy is .found to conlain about 0.6 at. pet interstitial boron, as evidenced by the tetragonality of this phase, and about 3.6 at. pct substilutional boron, us deduced from the lattice paratrieler decrease, the balance of the boron being precipitated as (Fe,Ni)aR. The austenitic Fe-Ni-B plznses also contain both interstitial and substitutional boron. Iron-Boron System. The phase diagram and related information about the solid solutions and intermediate phases in the Fe-B system are given by ansen,' Elliott.2 and Pearson.1 The equilibrium solid solubility of boron in both ferrite and austenite is quite small: the maximum solid solubility of 0.02 wt pct B (0.11 at. pct B) occurs in iron at the eutectic temperature of 1150°C. while the maximum solubility in a iron is less than 0.01 wt pct.l There is disagreement in the literature as to whether these solid solutions are substitutional or interstitial. Based on the measured activation energy of boron diffusion in iron, it appears likely that boron moves interstitially in austenite. 4 However, this observation does not rule out the possibility that some of the dissolved boron may also occupy substitutional sites in this phase. Investigations of internal friction of boron in iron have suggested that boron is interstitial there.' Shevelev, 5 on the other hand, reports a decrease in the ferrite lattice parameter with dissolved boron content, thus indicating a substitutional solution. Unfortunately. Shevelev's methods and analysis are unclear. Goldhoff and spretnak6 have measured the lattice parameters of pure iron and an Fe-0.005 wt pct B (0.027 at. pct) alloy at both room temperature (ferrite) and from 920° to 1200°C (austenite). They reporte: a lattice contraction in the ferrite of 0.0003 ± 0.0002 due to boron, thus indicating a predominately substitutional solution. Appreciable (0.0010 to 0.0060) lattice contractions were found in boron-containing austenites, but these effects were much larger than could be accounted for by the substitutional solution of all the boron present. Nickel-Boron System. Elliott 2 gives a summary of thephase diagram and recent work on this system. The solubility of boron in nickel reaches a maximum of 0.03 wt pct at the eutectic temperature of 1080°C. Iron-Nickel System. ansen' presents the equilibrium diagram for this system and also discusses the metastable austenitic and martensitic phases along with the a=? transformations. The lattice parameters of Fe-Ni ferrites have been recently redetermined by Abrahamson and Lopata.7 Their data, Fig. 1, show an unusual change in slope at about 1.7 at. pct Ni. Very few measurements of the lattice parameters of Fe-Ni martensites are available in the literature. The values of Roberts and Owen8 are considerably higher than those measured in the course of the present work: they find that a, is constant at 2.874? from 8 to 30 at. pct Ni. Both the slope change in the ferrite parameters and the occurrence of a maximum plateau in the marten-sitic lattice parameters vs composition denote the

Jan 1, 1970

By Gilbert L. Eggert

The effects of reactor irradiation on age hardening in a Cu-2 wt pct Be alloy have been investigated in two neutron-energy ranges. During some of the irradiations, specimens were exposed to high-energy fission neutrons which passed through a boron-10 shield; during other bombardments, the boron-10 was omitted and specimens were irradiated in a reactor thermal column, or the fuel configuration was modified to increase the thermal-neutron flux at a location in the core. Differences in length, X-ray diffraction angle, and hardness indicated that low-energy neutron irradiation made a small contribution to changes in the measured properties. The influence of defects generated by knock-om with less than the Brinkman critical energy or by prompt (n,y) recoil is suggested as the cause of this effect. EXPERIMENTS designed to test the effects of reactor irradiation on the properties of age-hardening alloys have to the present time employed fluxes un-differentiated according to neutron energy. Billing-ton and Siegell in 1950 were the first to perform such an experiment and to compare the results with those obtained by thermal aging. These authors concluded that precipitation in a Cu-2 wt pct Be alloy was not enhanced by the radiation. However, 4 years later, Murray and Taylor,2 working with specimens of the same Cu-2 wt pct Be alloy, reported that an increase in density, hardness, and resistivity which followed reactor irradiation resembled changes associated with thermal aging at about 100°C. (It should be noted that these authors reported that higher aging temperatures caused a decrease in resistivity.) cupp3 reported hardness results similar to those of Murray and Taylor. Koppenaal4 showed that irradiation-enhanced precipitation and irradiation defect hardening were not simply additive but that they acted separately in an irradiated alloy. Kernohan et a1.,5 working with Ni-Be, offered evidence that beryllium was removed from solid solution by reactor irradiation and suggested that the mechanism was one of increased diffusion through the use of vacancies in the structure. piercy6 also found that more precipitate particles were formed by fission-neutron irradiation of a Cu-Co alloy which contained a small amount of particles before irradiation. He proposed that the additional particles were caused by an appreciable amount of diffusion during the final cooling of displacement spikes. The retrogression of extant precipitate particles found by Murray and Taylor2 and Boltax7 as well as piercy6 indicated that nuclei were dissolved within a high-energy spike region and, upon resolidification of the perturbed volume, new nuclei precipitate and grow by enhanced diffusion. Bleiberg et al.' and Konobeevski et al.' explained phase changes obtained by irradiating fissionable alloys in terms of retrogression and re-precipitation in regions of high-energy spikes. Parsons and Balluffi10 used electron microscopy to verify that crystallization did indeed occur in displacement spikes which were formed in amorphous germanium by fast-neutron irradiation. The concept that low-energy neutron irradiation might cause structure-sensitive property changes in semiconductors by atomic recoil associated with the (n, y) reaction was first proposed by Schweinler" and walker." This thesis was tested by Cleland and crawford" and found to be valid. Coltman et al.14 exposed a variety of pure metals to thermal-neutron irradiation at cryogenic temperatures and attributed the resulting resistivity changes to the action of defects created by (n, y) recoil. The present work was undertaken to extend the concepts of Schweinler," walker," and Coltman et al.I4 to the case of an age-hardening alloy and to determine whether or not the action of defects produced by thermal-neutron irradiation would en-hance age hardening. EXPERIMENTAL PROCEDURE Omeea West Reactor Irradiations.* Thermal-

Jan 1, 1965

By Robert Maes, Robert de Strycker

The Fe-Ni-As phase diagram has been established by the study of about a hundred alloys, by microscopic observation, and by thermal analysis, with arsenic contents up to 50 pct. The iron and nickel arsenides present extensive solid-solution fields, owing to the substitution of nickel by iron and vice versa; the extent of the solubility field of each compound has been determined with an accuracy of ±1 pct. In the investigated range of compositions, the solidification reactions were established, and the temperatures of the invariant reaclions detevmined with a preciston of iZ°C in the most favorable and ±5°C in the least favorable cases. The isothermal lines of the liquidus surface have also been drazum, with an accuracy estimated at i5°C. Reactions in the solid state, which take place for the formation or the decomposition of certain phases , were investigated in detail. ThE constitution diagram of the Fe-Ni-As system is fundamental for the understanding of the properties of nickel speiss; these by-products of the extraction of certain nonferrous metals indeed often contain the three elements iron, nickel, and arsenic as main constituents. The Fe-Ni-As system has already been the object of earlier investigations. In 1932, Guertler and Savels-berg' have presented some elements of the ternary phase diagram, for arsenic contents up to 55 pct (all percentages in this paper are given in weight percent), including the vertical section FezAs-Ni&s2. This investigation is, however, incomplete and certain anomalies suggested the necessity to verify the results published by these authors: the section Fe2As-Ni5AsZ, for example, is presented as quasi-binary, with a field of complete miscibility in the solid state, even though these compounds do not have the same structure. Recently, ~useck' established an isothermal section at 800°C in the Fe-Ni-As system by X-ray diffraction and microscopic examination of water-quenched alloys. These techniques are sometimes inaccurate for the determination of the fields where alloys are liquid at the investigated temperature, and they may lead to erroneous conclusions when a compound exists at the investigated temperature but is not stable at room temperature and cannot be maintained by quenching. LIMITING BINARY PHASE DIAGRAMS The Fe-As constitution diagram has been the object of several investigations which have been reviewed by Hansen and Anderko.3 For the Ni-As phase diagram, a recent study has been effected by Yund.4 In this system, Heyding and calvert5 have determined the existence of a compound of unidentified structure at arsenic contents slightly higher than those corresponding to Ni5As2 and at temperatures lower than about 200°C; by analogy with iron and cobalt arsenides, this compound could correspond to the formula Ni2As, as suggested by Kulle-rud; although this is not definitely established. In the region of arsenic contents from 35 to 55 pct, Fried-rich7 detected anomalies in the solidification reactions; an interpretation of these anomalies was given by Hansen ,8 which assumed that the solidification reactions in practice are not in equilibrium, but are meta-stable. The main features of the Fe-Ni constitution diagram are the existence of a complete miscibility field, at least at high temperatures, for the fcc phase (which will be designated by My in the remainder of this work) and of a limited solubility field for the bcc phase (designated by Ma). EXPERIMENTAL METHODS The fundamental technique used in this investigation was microscopic observation, which allowed the determination of the reactions occurring during solidification of the alloys, and possible reactions in the solid state.

Jan 1, 1968

By O. K. Miniato, L. Massé, K. Nobe, J. S. Aronofsky, W. F. 213-000-000-016 Seyer

MUCH work has been done dealing with the effect of mechanical stress on electrode potential in an electrochemical system. The contradictory nature of the experimental results indicates the complexity of the problem although thermodynamic considerations show that a simple relationshir, should exist. In those systems where a gas was the electromotive active substance satisfactory agreement between theory and practice has been found. Des Coudres' found this to be so even when the active substance of the electrode, in this case mercury, was in the liquid state. In contrast, attempts to correlate theory and experiment for the solid state have met with a very limited success. The early workers in this field, Andrews,2 Walker and Dill3 used iron, certainly one of the most reactive of metals. Others have made use of less active metals such as copper and nickel. Recently Fryxell and Nachtrieb4 investigated the electrochemical behavior of gold and silver under both tensile and compressive stresses and concluded that it was doubtful whether true stress potentials could ever be measured. Much of the lack of success to measure the thermodynamic stress potential can be ascribed to the presence or formation of a complex film on the metal surface in contact with the electrolyte. Further, the theoretical stress potential is very small and therefore difficult to measure directly. Thus the calculated emf between a 24 B & S gage cold-drawn copper wire stressed with a weight of 1 kg and an unstressed portion of the same wire is only 2.60 X 10"7 volts. This is very small compared to that which can be produced by chemical reactions at the metal electrolyte interface which in turn can be so large as to mask completely the stress potential. Hence in this type of measurement all chemical side effects must be eliminated or reduced as much as possible. It was for this reason that the system copper-sodium chloride solution was selected for study. INSTRUMENTATION In the many preliminary experiments conducted, two major difficulties were encountered. The first was to measure the small electro-potentials to be expected and the second to obtain a suitable electrode surface. The conventional potentiometric method was found to be unsatisfactory for measuring the small emf expected. However, by using an L & N No. 2290 galvanometer having a resistance of 915 ohms consistent measurements were possible. The reference electrode was always the unstressed one made from the same sample of wire. The steady current flow was approximately 10-8 amp. Lewis and Randell5 have stated that for currents of the order of 10-8, if there is no sensible polarization, the measured emf may be taken as a reversible one. To check the galvanomenter readings an alternative method was devised to measure the potential difference between the wires. This involved a Liston-Falb d-c breaker amplifier model 10, an L & N k-2 potentiometer and a moving-coil galvanometer having a sensitivity greater than 0.1 µv (microvolt) per mm. To increase further the output voltage of the amplifier a d-c amplifier, model B. L.-932 was introduced into the circuit. This amplifier was in turn connected to a Brush recorder which had been calibrated previously by the test signals from the Liston-Falb instrument. These test voltages employed took into account the impedance of the input current. Unfortunately, this method had too low a sensitivity for measurement below 10 µv. Above this value the voltage agreed reasonably well with those obtained directly by the simple galvanometer method. The main advantage of the amplifier setup was that one did not have to wait until no deflection occurred on the galvanometer in the circuit when first exposing the wires to the solu-

Jan 1, 1959

By T. E. Seidel, A. U. MacRae

The dependence of the electrical and crystalline properties of silicon containing ion implanted boron atoms have been studied as a function of the incident dose, substrate temperature, and annealing tempera-ture. Hall effect studies show that the compensation due to defects is negligible after annealing at and above 500°C for a dose of 1013 ions per sq cm. Steps occur in the isochronal annealing curve for the sheet resistance at 300°C and 800°C and the mechanisms responsible for these steps are discussed. The range of the ions at 150 kev is 3500 * 5001. Electron diffraction studies on samples implanted with 150 ker ions show the existence of damaged (polycrystalline) silicon closer to the surface than the range of the ions. Etching and subsequent annealing of etched and unetched specimens suggest that the poly crystalline silicon is closer to the surface than the bulk of the distribution of ions. THE purpose of this study is to investigate some electrical and crystalline properties of ion implanted boron in silicon. Sheet resistance, Hall measurement, depth distribution by chemical staining, thermal probe and electron diffraction have been used to study the properties of samples implanted in a random direction with ions having energy up to 150 kev. The boron-silicon system has been the subject of considerable study'-7 due to its possible application in the fabrication of electronic devices. The implanted ions produce considerable crystalline damage to the substrate crystal before they lose most of their primary energy and come to rest. Fortunately, most, if not all, of this damage can be removed by subsequent annealing or by holding the substrate at an elevated temperature during the implantation process. Sheet resistivity measurements of the p-type layers produced by boron implantation into room-temperature silicon, reveal that the annealing occurs in a two-step process: the first occurring at -300°C and the second at -800°C.' Electron-microscope and low-angle electron diffraction studies of this damaged material indicate that the bombarding ions produce an amorphous silicon region about the trajectory of each ion.' At high doses, these damaged regions overlap and an amorphous surface layer results. Furthermore, the 800°C annealing step, appears to be associated with the elimination of this gross damage. The depth distribution of the as-implanted and also the annealed samples have been studied by an angle lap and staining technique as well as by Hall measurements.3-7 We find the experimentally determined ranges of the boron are less than those calculated by the Lindhard-Scharff-Schiott theorys (hereafter referred to as the LSS theory). Our results are in essential agreement with pre- vious results. In addition, we have made Hall measurements on samples bombarded with a low dose (2 x 1013 ions per sq cm) to minimize impurity banding effects, and find that deep ionized levels influence the carrier concentration and room-temperature hole mobility until the sample is annealed at temperatures above 500°C. Above this temperature, the data corresponds to that obtained when silicon is doped with boron by conventional techniques. We have also made a depth distribution determination of the crystalline damage due to the implanted boron by using glancing angle electron diffraction techniques. It was found that the gross damage depth distribution of heavily implanted samples is closer to the surface than the depth distribution of the electrically active boron. By removing this gross damage, without affecting the distribution of the implanted boron, we have determined that the 800°C annealing stage is not exclusively due to the improvement in the crystalline perfection of the amorphous material but also appears to be associated with the annealing of some point defects. These results and their relation to previous results are discussed in the following sections. IMPLANTATIONS Boron ions were implanted into silicon samples using an accelerator capable of operating from 10 to 150

Jan 1, 1970

By A. D. McMaster, M. L. Gimpl, N. Fuschillo

There is interest in the use of rhenium metal films as resistive elements in thin-film circcits, and already some zvork has been done using er)aporated rhenium films. It has been found that rheniim films protected from the atmosphere by an evaporated layer of silicon monoxide show excellent electrical stability. Unprotected films, however, are subject to aging- effects, notably the increase in electrical resistivity as a function of time. This phenomenon can be understood as primarily one of oxidation of the thin films. This paper is concerned with the study of the oxidation and crystallization behavior of such unprotected films. It has been found that the oxidation rates are a function of the substrate temperatures used during the deposition of Lhe metal films. The strictures observed in the films are correlated with the film resistivities and some data are presented to establish the existence of the various types of oxides of rhenium. ThERE is some interest in the use of thin films of rhenium metal as resistive elements in monolithic, thin-film integrated circuits. Some work has been done using evaporated films and it has been found that such films, if protected from the atmosphere by an evaporated layer of silicon monoxide, show excellent electrical stability up to temperatures of 500"." Rhenium films unprotected from the atmosphere tend to age and the electrical resistivity of the films increases as a function of time. Rhenium films, of the order of <100A thick, prepared by electron-beam evaporation techniques are found to oxidize very readily when exposed to dry air at room temperature. It would seem, therefore, that this aging phenomenon could be attributed to the oxidation of the metal films. In this investigation, the oxidation and crystallization behavior of thin films of rhenium evaporated onto silicon monoxide substrates were studied as a function of the substrate temperatures used during the evaporation. The films were examined using electron-microscopy and electron-diffraction techniques. EXPERIMENTAL RESULTS Rhenium metal was evaporated onto suitable prepared substrates which were heated to various temperatures. The evaporations were performed in a vacuum of approximately 5 x 1CT5 torr. The evaporation was carried out at a rate of approximately 10A per omin. The final film thickness was approximately lOOA and the resistance ranged from 5000 to 10,000 ohms per square. The substrates used for supporting the metal films were made by evaporating 75A of silicon monoxide onto freshly cleaved mica. The silicon monoxide film was then floated off the mica by immersing the composite in water. The film could then be picked up on a clean nickel grid. Silicon monoxide substrates were chosen because of their similarity to quartz and glass substrates commonly used for making thin-film resistors. Fuschillo, Gimpl, and McMas-ter have also shown that silicon monoxide films have only minor structural changes at temperatures up to 800°C. This fact simplified the interpretation of any changes observed in the electron micrographs or electron-diffraction patterns obtained from the deposited rhenium films. After the evaporations were completed, the substrates were cooled to room temperature, except where noted differently, before the coated substrates were removed from the vacuum system. All aging of the deposited films was done in a desiccator. The evaporated films were examined in an electron microscope equipped with a hot stage that would permit continuous observations of the samples up to temperatures of 1000°C. RESULTS A series of electron micrographs of the rhenium films deposited on the silicon monoxide substrates are shown to Figs. 1 to 3. In all cases, the metal films are approximately 100A thick and the micrographs were taken 1 hr after the deposition was completed. here was no apparent structure in the films deposited on the substrates held at the higher temperatures. The

Jan 1, 1967

By F. P. Bullen

Empirical relationships between fracture stress, orientation angle, and diameter of crystal have been determined at 77°K. Orientation ranges of markedly different behavior were found—a law of constant normal stress&apos; of value a (diameter)-1/2 for the fracture of ductile crystals, and a condition of shear stress (or strain) for more brittle crystals. The observations are not consistent with current theories. An interpretation is advanced which is also applicable to observations on the effect of prestrain at room temperature on the subsequent fracture stress at 77°K and to the effect of cyclic stressing on the cleavage strength.&apos;&apos; The law of constunt normal stress&apos; and the brittle ductile transition are also explained. The interpretation is more consistent with the initiation of cracks by intersecting dislocations than with theories based on stress -concentration by dislocation arrays. ZINC single crystals are particularly suited to the study of cleavage because fracture occurs on the basal plane over a wide range of crystal orientations. Analysis of the conditions of stress and strain at fracture in crystals of different orientations should indicate which parameters control the cleavage process. Unfortunately, controversy has arisen over the correct empirical relationship between tensile fracture stress and orientation. Schmid&apos;s observations1,2 favored a &apos;law of constant normal stress&apos;, as observed in other materials.2 For zinc, however, the observed values are far below the theoretical strength and cannot represent the true limit of cohesion between neighboring atomic planes. Hence, the interpretation of such a &apos;law&apos; is not straightforward. Deruyttere and Greenough3,4 found a complex variation between tensile fracture stress and orientation; this variation did not agree with a &apos;law of constant normal stress&apos;. Two theories have been advanced to account for their observations: a) the propagation of cracks from low-angle boundaries,5 and b) the release of energy from piled-up dislocations during crack-propagation.4 The present work resolves the apparent discrepancy between the observations and shows that neither of the above theories are applicable to the tensile fracture of zinc single crystals. A phenomenological explanation, along the lines suggested by Gilman,&apos; is advanced and successfully applied to previously unexplained effects. EXPERIMENTAL DETAILS &apos;Crown Special&apos; redistilled zinc was used, except for one comparison series op tests using &apos;Tadanac&apos; electrolytic zinc. Crystals of 1 mm diam, subsequently called &apos;1 mm crystals&apos;, were grown from the melt in vacuo in precision-bore Pyrex tubes internally coated with graphite. Several specimens 1 in. long were cut from each crystal and chemically polished. Jigs were used to minimize handling strains, and crystals were mounted in the Polanyi machine the day prior to testing to allow recovery from any such strains. One-mm crystals were chemically polished for long periods to obtain 0.1 mm (approx) crystals. One-mm crystals were cemented into miniature gimbals by &apos;Araldite&apos; casting resin. The Appendix gives the reasons for using gimbals and the results obtained by other methods. More complete details of all techniques are given elsewhere.7 The symbols and terminology used are as follows: X = orientation angle (angle between tensile axis and line of greatest slope in the basal plane). T = tensile stress (on true cross-section) S,N = shear and normal stress (components of T with respect to the basal plane) ? = shear strain D = crystal diameter. The subscript &apos;f&apos; will be used to denote values at fracture. PART I-ANNEALED CRYSTALS EXPERIMENTAL OBSERVATIONS One-mm crystals were used to establish the variation of fracture stress at 77°K with orientation at fracture (Xf), Fig. 1. For 18 deg = Xf = 55 deg, a &apos;law of constant normal stress&apos; was observed. For Xf > 55 deg, the fracture condition approximated to a constant shear stress. At Xf< 18 deg, twinning occurred before fracture so that the results were not typical of homogeneous single crystals,4,8— such specimens will not be considered herein. The dependences of fracture stress upon Xf were of similar type for 6 mm,* 1 mm, and 0.1 mm crystals,

Jan 1, 1963

By Robert D. Pehlke, Weldon L. Daines

The reduction of manganese oxide from a basic slag by silicon dissolved in liquid iron at steelmaking temperatures was studied to determine the rate-controlling step for the process. The experiments were carried out under an argon atmosphere in a resistance-heated vertical-tube furnace. The two liquid phases, slag and metal, were held in zirconia crucibles. Sampling and chemical analysis of the slag phase led to time-concentration curves for the system. Results obtained by varying parameters such as temperature, stirring rate, concentration, and melt geometry defined the limiting reaction mechanism. The reduction of manganese oxide by silicon is a fast reaction and reached equilibrium within 90 min. The rate of stirring has a marked effect on the reaction rate, while, on the other hand, the effect of temperature is very small. This identifies the rate-controlling step as diffusion rather than interfaciul chemical reaction. The variation of other parameters revealed that a) diffusion of manganese in the iron phase is the slow step, b) the value of D/6 for manganese in iron at 1550°C is 7x 10-4 cm per sec, c) the energy of activation for the apparent rate constant is 7 kcal per mole, and d) increasing the amount of silicon in the iron decreases the diffusion coefficient of manganese. THE equilibrium relations pertinent to the reduction of manganese oxide from a steelmaking slag by silicon dissolved in liquid iron have been studied, but little is known about the mechanisms that control the rate of the process. The purpose of the present investigation was to study the rate of reduction by silicon and to determine the rate-limiting step. The effects of stirring rate, temperature, composition, and melt geometry were investigated as a means of identifying the controlling step. On the laboratory scale, relatively little work has been done in the area of slag-metal kinetics, primarily because of the problems confronted in attempting to contain liquid slags and metals in laboratory crucibles at steelmaking temperatures. Since graphite is an ideal material for a crucible, several investigations have been carried out on the reduction of various oxides from a slag by carbon in graphite-saturated iron and on the transfer of sulfur between a slag and graphite-saturated iron. Most of this work has been performed in induction furnaces. Studies where the container was not graphite are extremely limited. A single kinetic study of manganese transfer between molten iron and basic slags was carried out by Sano, Shiomi, and Matsushita.&apos; These investigators prepared calcium oxide and titanium oxide crucibles to contain the two-phase system. Only a few experiments were carried out and the results had to be treated qualitatively. Despite the paucity of kinetic data, a large quantity of information is available in the literature concerning the thermodynamics2-12 and physical properties&apos;3-21 of the slags containing manganese oxide and the dilute liquid iron alloys containing manganese and silicon which were involved in this research program. EXPERIMENTAL METHOD A vertical-tube resistance-heated furnace was used in this investigation to study the slag-metal reaction Although most previous slag-metal studies were carried out in induction furnaces, a resistance furnace has several advantages including better control of temperature and stirring rate. Hence, a resistance furnace was selected for this study, and its design is shown schematically in Fig. 1. Slip-cast, fine-grained, low-porosity, lime-stabilized cubic zirconia crucibles were used for the kinetic experiments. The crucibles were 4 1/2 in. high and 2 1/8 in. OD with a 1/16-in. wall. The crucibles were only slightly

Jan 1, 1969

By H. H. Kaveler, W. R. Evans, Jack Tarner

The geological features, development history and engineering detail of the Shuler Field and the results of approximately two years of unitized operation of the Shuler Jones Sand Pool, were discussed in a prior publication.&apos; The purpose of this paper is to present the results of pressure maintenance in the Shuler Jones Sand Pool after nine years of unit operation. GENERAL INFORMATION The Shuler Jones Sand Pool is located in and about Section 18, Township 18 South, Range 17 West, Union County, Ark. The pool was discovered .in September, 1937, unitized in February, 1941, and subjected to gas injection operations in July, 1941. Water was first returned to the reservoir in July, 1944. The reservoir is an anticlinal trap covering about 4,000 acres. The 154,000 acre-ft of sandstone initially consisted of approximately 150,000 acre-ft of productive oil zone and 4,000 acre-ft of gas-cap. The average depth of production is 7,400 ft. Maximum closure of the reservoir is 135 ft and the oil column lies between a gas-oil contact at -7,270 ft and a water-oil contact at -7,370 to -7,380 ft. The field is approximately four miles long. east and .west, and one and one-half miles wide. The sand grains are angular and vary from fine to medium size. The porosity of the sandstone averages 20.2 per cent. The specific permeability averages 400 md. Some zones have as high as 30 per cent porosity and specific permeability of 4,000 md. The reservoir rock is not uniform in character but consists of sandstone zones interspersed with shale. The variation in rock characteristics is evident in the electric log and core analyses presented in the original publication. Asphalt present in the pore space of the sandstone limited the reservoir to the southeast and apparently blocked any encroachment of water from that direction. The initial reservoir pressure at a subsea depth of 7,300 ft was 3,520 psi. The reservoir temperature was 198ºF. Initially, the solution gas volume was 765 cu ft per bbl and the reservoir volume factor was 1.45. The gas solubility and formation-volume-factors of the reservoir liquid are related with reservoir pressures above 300 psi as follows: Solution gas, cu ft per cu ft, S = 0.0334 P + 18.65 Formation volume factor of reservoir oil, FVF = 8.0 x 10 -5 P + 1.168 Gas volume factor, standard cu ft of gas equivalent to one cu ft of gas at reservoir conditions of temperature and pressure, F = .062 P - 4 Pressure (P) measured in psia. The equation for the gas volume factor presented above is based on a direct measurement of a sample of the gas and is a correction of that used in the original paper. The gravity of the oil produced is from 32 to 34" API. CALCULATION OF INITIAL OIL IN PLACE The Jones Sand production history is interesting because it lends itself to analysis by material balance. Production statistics from discovery of the Jones Sand through 1949 and material balance calculations of the initial stock tank oil in place are shown in Table I. The usual procedure in testing the application of material balance calculations is to compute the apparent initial volume of oil in place, using production and pressure information obtained at different time periods. If the apparent oil in place volumes computed increase with successive time periods, water encroachment is indicated and approximations must be mads to correct for its influence. The first requirement in utilizing such calculations is reliable reservoir pressure, accumulated gas, oil and water production, and PVT data. Calculations of apparent oil in place in the Jones Pool, based on field data

Jan 1, 1951

By W. R. Evans, H. H. Kaveler, Jack Tarner

The geological features, development history and engineering detail of the Shuler Field and the results of approximately two years of unitized operation of the Shuler Jones Sand Pool, were discussed in a prior publication.&apos; The purpose of this paper is to present the results of pressure maintenance in the Shuler Jones Sand Pool after nine years of unit operation. GENERAL INFORMATION The Shuler Jones Sand Pool is located in and about Section 18, Township 18 South, Range 17 West, Union County, Ark. The pool was discovered .in September, 1937, unitized in February, 1941, and subjected to gas injection operations in July, 1941. Water was first returned to the reservoir in July, 1944. The reservoir is an anticlinal trap covering about 4,000 acres. The 154,000 acre-ft of sandstone initially consisted of approximately 150,000 acre-ft of productive oil zone and 4,000 acre-ft of gas-cap. The average depth of production is 7,400 ft. Maximum closure of the reservoir is 135 ft and the oil column lies between a gas-oil contact at -7,270 ft and a water-oil contact at -7,370 to -7,380 ft. The field is approximately four miles long. east and .west, and one and one-half miles wide. The sand grains are angular and vary from fine to medium size. The porosity of the sandstone averages 20.2 per cent. The specific permeability averages 400 md. Some zones have as high as 30 per cent porosity and specific permeability of 4,000 md. The reservoir rock is not uniform in character but consists of sandstone zones interspersed with shale. The variation in rock characteristics is evident in the electric log and core analyses presented in the original publication. Asphalt present in the pore space of the sandstone limited the reservoir to the southeast and apparently blocked any encroachment of water from that direction. The initial reservoir pressure at a subsea depth of 7,300 ft was 3,520 psi. The reservoir temperature was 198ºF. Initially, the solution gas volume was 765 cu ft per bbl and the reservoir volume factor was 1.45. The gas solubility and formation-volume-factors of the reservoir liquid are related with reservoir pressures above 300 psi as follows: Solution gas, cu ft per cu ft, S = 0.0334 P + 18.65 Formation volume factor of reservoir oil, FVF = 8.0 x 10 -5 P + 1.168 Gas volume factor, standard cu ft of gas equivalent to one cu ft of gas at reservoir conditions of temperature and pressure, F = .062 P - 4 Pressure (P) measured in psia. The equation for the gas volume factor presented above is based on a direct measurement of a sample of the gas and is a correction of that used in the original paper. The gravity of the oil produced is from 32 to 34" API. CALCULATION OF INITIAL OIL IN PLACE The Jones Sand production history is interesting because it lends itself to analysis by material balance. Production statistics from discovery of the Jones Sand through 1949 and material balance calculations of the initial stock tank oil in place are shown in Table I. The usual procedure in testing the application of material balance calculations is to compute the apparent initial volume of oil in place, using production and pressure information obtained at different time periods. If the apparent oil in place volumes computed increase with successive time periods, water encroachment is indicated and approximations must be mads to correct for its influence. The first requirement in utilizing such calculations is reliable reservoir pressure, accumulated gas, oil and water production, and PVT data. Calculations of apparent oil in place in the Jones Pool, based on field data

Jan 1, 1951

By S. R. B. Cooke, H. S. Choi, D. H. Harraway, I. Iwasaki

The mineralogy of natural iron ore samples and their slimes have been investigated and the nature of slime interference in iron ore flotation has been studied. The results have been correlated with the flotation behavior of a natural ore sample. Various conclusions have been reached as a result of these studies. In the flotation of iron oxide ores, desliming is generally considered to be an essential step to successful separation, irrespective of whether the iron oxide or siliceous gangue minerals are to be floated, although some workers have found empirically that certain collectors and reagent combinations are less sensitive to the presence of slime than others. The detrimental effect of slime is considered to be twofold. First, the presence of slime presupposes a high reagent consumption because of high specific surface. When clays are present and when cationic collectors are used abstraction by ionic exchange may augment this condition. Attempts to compensate by the addition of large amounts of reagent result in only partial correction. Second, slime coatings on granular particles tend to interfere with the bubble-mineral contact. The nature of slime coatings in flotation is quite complex and has been the subject of considerable study; an attempt was recently made by Fuerstenau et al.&apos; to relate the slime-coating density with flotation recovery and with the properties of the electrical double layer at the mineral surfaces. Although major constituent minerals in the oxidized iron ores of the Mesabi and Cuyuna ranges are hematite and goethite (limonite) as the iron oxides, and quartz and chert as the siliceous gangue, very little is known of the mineralogy and of the chemical and physical characteristics of the slimes, and still less of the interaction between slimes, collector, and the mineral surfaces. For pragmatic reasons iron ore slimes are defined as — 20p material, based upon the calculated settling velocity of a quartz sphere of the stated diameter, and of all other equal-settling mineral particles. Active slime interference with flotation is usually attributed to particles 5p in size or finer, the extent of such interference appearing to depend not only on the mineralogy but also on the size distribution of each mineral in the slime fraction. The objective of this work was to acquire a more specific knowledge of the constitution of iron ore slimes and of their role in flotation. The mineralogi-cal composition of natural slimes was obtained by differential thernal analysis (hereinafter referred to as DTA), electron microscopy, and chemical and X-ray analyses. Some flotation tests were made on natural ore samples. The surface properties of several constituent minerals were investigated by electrophoretic measurements and by determination of the adsorption of some typical flotation collectors. Finally, simplified flotation tests were made on granular goethite and quartz in the presence of various artifically prepared slimes; the results were compared with laboratory flotation tests made on natural ores. MATERIAL AND METHODS Mineralogy of Some Iron Ore Slimes: Samples of two wash-ore tailing::, hereinafter identified as A* and B, *Sample A of the present investigation 18 the same am ore A in ref. 3. of a wash ore C, and of a paint rock D, all from the Mesabi range, were selected for investigation on the basis of prior information concerning their flotation behavior. The two wash-ore tailings, when deslimed, were known to respond well to flotation, whereas the wash ore was high in goethite, tended to be slimy, and responded poorly to flotation. The paint rock also exhibited sliming tendencies, and was suspected to contain relatively large quantities of clay minerals because of its high A1203 content. Gruner states that the paint rock of the Mesabi frequently contains kaolinite. To ascertain the relative sliming tendencies of each sample a standardized desliming method was employed. All samples were ground through 65 mesh using jaw and rolls crushers. A 500-g sample of each

Jan 1, 1962

By T. M. Morris

THE rate of flotation of solid particles determines the percentage recovery of these particles which can be obtained during a given time interval. It is an established fact that the recovery is greatest in the fine sand size range and falls off on either side of this size range. It is also a fact that the history of the development of concentrating devices has been marked by a desire to recover the small particles: tables were developed to treat material too fine to recover in jigs; flotation recovers material too fine to be recovered on tables. As our ores become more complex and require finer grinding, a greater proportion is in the slow-floating size range. It is therefore of economic importance that the effect of size of particle upon rate of flotation be studied. Many studies have been made along this line. The present investigation attempts to quantify the rate of flotation by means of a rate equation, and then compares the effect of size upon the rate of flotation. It was found that the flotation rate constant increases with increase in diameter of particle in the size range smaller than the optimum size particle. The flotation rate constant decreases with an increase in diameter of particle in the size range coarser than the optimum size particle. This suggested two different actions taking place, and these are discussed. Suggestions for further work in order to improve the flotation rate of both fine and coarse particles are made. The usual method of expressing rate is to plot cumulative percent recovery vs time. If we knew the equation of this kind of curve we could replot it as a straight line, and the slope of the line would be an index of the magnitude of the flotation rate. It is easier to compare straight lines than curves. The basis used for obtaining the equation of the recovery vs time curve is the law of mass action. This law states that the "rate of a chemical reaction is proportional to the `active masses&apos; of the reacting substances present at any given time." This, of course, implies a constant temperature. We can modify this for our use by using the term flotation reaction instead of chemical reaction and the term floatable particle instead of active masses. [ ] where C denotes concentration of particles, t denotes time, k denotes a proportionality constant. If the exponent of C is 1, then we have a first order rate reaction. If the exponent of C is 2, then we have a second order rate reaction. For a first order rate reaction, we obtain, after integration, [ ] where k is again a proportionality constant and has the dimension of the reciprocal of time. C, is the original concentration or weight or percentage of floatable particles. C, is the concentration or weight or percentage of floatable particles remaining in the flotation cell after time t. If all particles of the mineral to be floated were capable of floating we could take C, as 100 and C, would be 100 - R, where R is the cumulative percentage recovery of mineral at time t. But it is not usual for all of the particles to be capable of floating, because of surface oxidation, etc. Therefore, we must introduce a factor x which is the percentage of unfloatable mineral. Hence the first order equation is [ ] It has been proposed by various workers1-3 that this equation describes the flotation rate. More recently N. Arbiter4 states that a second order rate equation fits the recovery vs time curve more closely than does a first order rate equation. Morris&apos; has discussed the evidence presented for this statement. It has been concluded that the first

Jan 1, 1952

By W. S. Hyler, W. L. Bruckart

The powder metallurgy and arc-cast types of wrought molybdenum stock were studied in rotating beam fatigue. Endurance ratios of unnotched specimens after 5x10 cycles were found to be 0.74 and 0.81, respectively. Fatigue notch factors (K,) of 1.36 and 2.05, respectively, were obtained on V-notched specimens having a theoretical stress-concentration factor Kt = 3.1. MOLYBDENUM and its alloys are rapidly gaining importance as engineering materials of construction for high temperature applications. AS a wrought material, molybdenum and its alloys are outstanding above 1800°F. It is necessary, however, with molybdenum to provide elevated temperature oxidation protection. This is currently being studied by a number of investigators. Thus far, there have been no published data on the fatigue behavior of molybdenum either at room temperature or at elevated temperature. The knowledge of fatigue behavior, particularly notched fatigue behavior, becomes increasingly important as the engineering importance of a material increases, especially from the design standpoint. The work described here was directed toward determination of the notched and unnotched rotating beam fatigue characteristics of molybdenum at room temperature. Also, it was desired to learn whether any difference exists between wrought molybdenum of the powder metallurgy and the are-cast types. Fabrication History of Bar Stock For this work, bar stock was procured from Climax Molybdenum Co. (are-cast type) and from Westing-house Electric Corp. (powder metallurgy type). The processing histories of these materials are listed in Table I. The first lot of are-cast molybdenum was deoxidized by aluminum additions. The second lot was deoxidized by carbon." Both lots of the powder Microstructure A microscopic examination of these materials, as received, revealed the powder metallurgy molybdenum to be free of inclusions and to be finely fibered. On the other hand, the are-cast C molybdenum possessed numerous carbide inclusions, and the arc-cast A appeared to have coarse grained fibers. These are shown in Fig. 1. Owing to the large apparent difference in fineness of fiber between the are-cast A and the powder product and are-cast C, a check was made of the recrystallized grain sizes to determine whether these differences persisted. A series of recrystallization anneals revealed mixed grain sizes in both the are-cast A and the powder product. Variations in grain diameter of as much as 50 times were found after full recrystallization at 1200°C for 30 min. There was no distinction between the two. Arc-cast C was not checked. Room Temperature Mechanical Properties Prior to subjecting the materials to fatigue tests, room temperature mechanical properties were determined. These data, together with the tensil: strength of the notched bars, data,togetherare listed in Table tensil: There were no significant differences in the tensile strengths of the two types of molybdenum. However, the powder metallurgy material was generally more ductile and yielded at a somewhat lower stress than the arc-cast material. Tensile strengths of the notched specimens indicated a slightly greater notch strengthening effect in the are-cast C than in the powder product, lot 2. Room Temperature Fatigue Properties Sample Preparation: Specimens were prepared for use in R. R. Moore rotating beam fatigue machines. These specimens had a continuous radius test section with a minimum diameter of 0.260 in. The specimens were prepared by grinding to shape and polishing to produce a smooth unworked surface. Polishing consisted of rotating a disk in the continuous radius section on which were attached, successively, emery belts of 240, 400, and 600 grit. The specimens were slowly rotated during the operation. The belt speed was high, and rotation was such that polishing scratches were longitudinal. Unnotched Fatigue Properties: Unnotched fatigue data were obtained from a number of specimens of each of the four lots of molybdenum. The results of the tests are presented in Fig. 2. From this figure,

Jan 1, 1956