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By E. S. Bartlett, D. N. Williams

QUANTITATIVE values for the oxidation rate of unalloyed molybdenum in air at temperatures above the melting point (1460°F) of the characteristic oxide are contained in the literature as a result of previous investigations. Lustman' reported values corresponding to 0.36 in. penetration per day (IPD) at 1500 and 1600°F in still air, noting essentially no variation in rate with temperature. Jones, Spretnak, and Speiser' reported values corresponding to 0.14 and 0.13 IPD at 1500 and 1800°F, respectively, in still air, attributing the decreased oxidation rate at higher temperatures to a lesser accumulation of the corrosive molten oxide on the surface at the higher temperature as a result of increased volatilization rate. Harwood3 ecently summarized work in the field, presenting generalized data corresponding to 0.48 to 0.96 IPD at 1800°F and 0.55 to 0.83 IPD at 1700°F in slowly flowing air. In a recent program at Battelle, it became desirable to know more about the characteristic oxidation behavior of molybdenum under varying conditions of temperature and atmosphere. Using oxidation-test apparatus designed for dynamic, continuous recording of weight change during testing,' values for the oxidation rate of molybdenum were obtained at temperatures from 1400 to 2150°F. In addition the effect of air flow on the oxidation rate was studied briefly at temperatures of 1600, 1800, and 2000°F. Exhaust of the contaminated atmosphere from the oxidation chamber was effected by an impeller pump attached to a 3/16-in.-diam opening in the oxidation chamber. The volumetric exhaust rate (cubic feet per hour) was normally maintained slightly in excess of the input rate to avoid condensation of MOO,,' on the sample suspension rod. The entering atmosphere was preheated prior to admission to the oxidation chamber by a 1 1/2-in.-diam cup packed with shredded asbestos. The experimental data are presented in Table I. Comparing conditions 2 and 3 (taking into account the temperature difference) and conditions 8 and 9. shows that in the absence of forced exhaust an atmosphere of moving air results in greater oxidation rate than a stagnant atmosphere. The use of forced exhaust, as shown by comparing conditions 3 and 4 and conditions 14 and 15: resulted in an even greater increase in oxidation rate. By virtue of the size of the atmosphere input and exhaust openings, it was calculated that the exhaust velocity was about 60 times that of the input velocity for essentially equal volumetric flow rates. Because of the proximity (about 3/4 in.) of the exhaust port to the specimen, it is logical to assume that cleansing of the atmosphere immediately surrounding the specimen was accomplished much more efficiently by the exhaust flow than by the input flow at a constant-volumetric flow rate. Also, it can be seen by comparing conditions 4 through 7 and conditions 11 through 13 that increasing the rate of atmosphere flow (by increasing input velocity with a proportional increase in exhaust velocity) above some optimum value has little, if any, further effect on the oxidation rate. These results suggest that there is a maximum oxidation rate for molydenum at a given temperature which is obtained when conditions are maintained such that the partial pressure of MOO3 in the atmosphere surrounding the specimen is at a low value. By controlling the partial pressure of MOO, surrounding the sample, it is possible to control the rate of volatilization of MOO:, from the surface. This, in turn, affects the rate of oxidation, since the thickness of the MOO3 layer determines the amount of oxygen which will be able to reach the reaction surface.' When the liquid oxide layer is less than some critical thickness, i.e., when the volatilization rate is high, enough oxygen is transported to the active surface to permit oxidation to proceed at the maximum rate allowed by the kinetics of the oxidation reaction. However, if the volatilization of MOO,, is suppressed, the thickness of the layer of MOO3 on the surface increases, and the diffusion of oxygen through the oxide layer becomes the rate-controlling step in the oxidation process. The lack of agreement between the present results and those of previous investigators is presumed to be due to differences in removal of the oxidation product (Moo,) from the immediate vicinity of the sample. By comparing conditions 1, 5, 10, 12 and 14, it is seen that when forced exhaust was used the oxidation rate of molybdenum increased with increasing temperature. A rapid increase was observed between 1400 and 1600°F, attributable to the effects

Jan 1, 1959

By Paul F. Kerr, Raymond F. Robinson

Uranium mineralization occurs in the footwall of the Sunshine vein from the 2900 to the 3700 level. Veinlets of uraninite associated with pyrite and jasper have been so extensively divided and recemented that units more than a few feet in length are seldom observed. The wall rock is St. Regis quartzite of the Belt series. The age of the uraninite, on the basis of isotopic analyses, is 750 * 50, which agrees with geological data suggesting that phases of the Sunshine mineralization are pre Cambrian. THE Sunshine mine in the Coeur d'Alene district, Idaho, is well known for its silver-bearing veins but prior to the summer of 1949 had not been recognized as a possible source of uranium. At that time, during a geiger counter reconnaissance by T. E. Gillingham, R. F. Robinson, and E. E. Thurlow, high radioactivity was noted and radioactive specimens were collected from the footwall of the Sunshine vein.' The detection led to the identification of uraninite-bearing veins, since explored jointly by the Atomic Energy Commission and the Sunshine Mining Co. After the occurrence was noted, the geology of the uranium deposit was studied by the Sunshine staff, and a laboratory examination of the ores was conducted at Columbia University. Several types of laboratory work were undertaken. Differential thermal curves were made of selected siderite samples and results from many more were secured through the work of Mitcham.2 X-ray diffraction and X-ray fluorescence analyses were employed on uraninite, jasper, and siderite. Chemical analyses were made through the cooperation of the Division of Raw Materials of the Atomic Energy Commission. General Geological Features Several silver-bearing veins cut the overturned north limb of the Big Creek anticline as mapped by Shenon and McConne1,³ while the Osburn fault, a long-recognized regional feature about a mile away, marks the north boundary of the Silver Belt. The Sunshine vein, Fig. 1, has a south dip more or less parallel to the 60" axial plane of the fold and cuts rocks of the Belt. Series, starting with the Wallace formation near the surface, continuing downward through the St. Regis formation, and probably extending into the Revett quartzite which lies below the bottom or 3700-ft level. The limb of the anticline is locally modified by secondary folds, one being prominently exposed in the uranian area along the Jewel1 crosscut near the Sunshine vein. Crumpling of the limb resulted from compression which formed the anticline and probably preceded the faults in which the vein deposits accumulated. Evidence of drag along these faults points to reverse movement in the uranium-bearing area and elsewhere. This is true of major faults in the mine workings, and the majority of faults which can be mapped, as pointed out by Robinson.' The St. Regis formation, as measured in the mine, appears to have an initial thickness of some 2000 ft, but the apparent thickness due to thickening during folding is some 3400 ft. Along the Sunshine vein the purple and green rocks characteristic of the Wallace formation in the nearby Military Gulch section p. 37 of ref. 5) have been completely bleached because of introduced sericite. Hydrothermal solutions acting on the wall rock have substituted for the original color a pale greenish cast, although no pronounced mineralogical change has resulted, as Mitcham has observed.' The silver and the uranium depositions appear to belong to distinct epochs resulting from several periods of emplacement. Likewise, multiple periods of deformation account for the faulting. Uraninite is generally associated with silicification, while silver . mineralization accompanies carbonate veins. Rarely, uraninite may be found in a matrix of siderite. Ordinarily uraninite formed prior to ar-gentian tetrahedrite. Where clusters of veins form a stockwork, uraninite-jasper veins often favor one trend while tetrahedrite-siderite veins favor another. During deformation, brecciation of the St. Regis quartzite provided openings between broken rock fragments for precipitation from vein-forming solutions. Fractures due to major breaks were filled during the first stages of vein formation, while later deformation displaced the first veins and provided new channels along which further mineralizing solutions proceeded. The uraninite veins, as the first formed, have suffered fracturing, displacement, and segmentation. Uranian vein segments uncut by faults and more than a few feet in length are rare or nonexistent. Siderite veins are more massive and often extend without a break for tens and even hundreds of feet. In general they show much less segmentation. While the siderite is usually later, there is an overlap in the periods of deposition, some earlier siderite veins being extensively segmented in much the same way uraninite veins have been broken. Vein silica is more extensively distributed than the uranium and iron mineralization it carries. Along the vein course concentrations of uraninite frequently fade away and barren white quartz continues, the transition often occurring within a few feet along strike or down dip. An example appears on the 3700-ft level where a uraninite vein, see Fig. 2a,

Jan 1, 1954

By Cyril Stanley Smith

On the 6th of February 1684, Dr. Martin Lister mentioned at a meeting of the Royal Society1 that "brass is magnetical," and promised to give an account of that assertion at some other time. He repeated his promise but never fulfilled it, and it was left for William Arderon2 to show, in 1758, that brass could be made magnetic by hammering and that it would retain polarity after magnetizing. Twenty-seven years later Caval103,4 examined the matter in great detail. Working with cast calamine brass, he showed that it could be made magnetic by hammering and nonmagnetic by subsequent annealing at a red heat. He found that annealing at a very high temperature caused the samples to lose their magnetic quality permanently, even after subsequent cold-working, but that remelting and cold- working restored it. He encountered some samples of brass that could not be rendered - magnetic by any treatment. Experiments in which these were remelted with iron additions gave negative results, and Cavallo concluded that iron impurity was not the cause of the magnetism. He worked with 50-grain (3-gram) samples melted under the blowpipe, hence cooled very quickly. Bennet5 made whole crucible charges from copper and zinc, and found _ the resulting brass ingots to be magnetic only when iron had been added and then only after cold-working. All these observations applied to material in the cast condi- tion, in which coring would produce a continuous spectrum of composition and cooling would result in varying degrees of precipitation. This knowledge of the subject seems to have been forgotten in the nineteenth century. The older brass was made by the calamine process and frequently contained iron in amounts of 0.5 per cent or more, absorbed from the impure ore with which the copper and charcoal were heated in making the brass. When metallic zinc became available in commercial quantities, calamine brass gradually disappeared, and with it the knowledge of its curious magnetic properties. Only when sensitive apparatus replaced the compass needle of the earlier investigators could the effects be detected in relatively pure metal. The effect of cold-working in inducing ferromagnetism was rediscovered by Bitter8 in 1930 in a sample of impure copper, and this was confirmed by Lowance and Constant: Honda and Shimizu, l0,11 and others. In the same year, Tammann and Oelsen12 showed that copper-rich copper-iron alloys after certain heat-treatments could be rendered ferromagnetic or made more strongly ferromagnetic by cold-rolling. Kussman and Seeman13 showed that the change of susceptibility of relatively pure copper on cold-working was associated with the iron content, and concluded that actual precipitation of iron was caused by cold-working, which is a satisfactory theory until one considers the improbably high rate of diffusion that this would involve. When studying precipitation phenomena in

Jan 1, 1942

By Cyril Stanley Smith

On the 6th of February 1684, Dr. Martin Lister mentioned at a meeting of the Royal Society1 that "brass is magnetical," and promised to give an account of that assertion at some other time. He repeated his promise but never fulfilled it, and it was left for William Arderon2 to show, in 1758, that brass could be made magnetic by hammering and that it would retain polarity after magnetizing. Twenty-seven years later Caval103,4 examined the matter in great detail. Working with cast calamine brass, he showed that it could be made magnetic by hammering and nonmagnetic by subsequent annealing at a red heat. He found that annealing at a very high temperature caused the samples to lose their magnetic quality permanently, even after subsequent cold-working, but that remelting and cold- working restored it. He encountered some samples of brass that could not be rendered - magnetic by any treatment. Experiments in which these were remelted with iron additions gave negative results, and Cavallo concluded that iron impurity was not the cause of the magnetism. He worked with 50-grain (3-gram) samples melted under the blowpipe, hence cooled very quickly. Bennet5 made whole crucible charges from copper and zinc, and found _ the resulting brass ingots to be magnetic only when iron had been added and then only after cold-working. All these observations applied to material in the cast condi- tion, in which coring would produce a continuous spectrum of composition and cooling would result in varying degrees of precipitation. This knowledge of the subject seems to have been forgotten in the nineteenth century. The older brass was made by the calamine process and frequently contained iron in amounts of 0.5 per cent or more, absorbed from the impure ore with which the copper and charcoal were heated in making the brass. When metallic zinc became available in commercial quantities, calamine brass gradually disappeared, and with it the knowledge of its curious magnetic properties. Only when sensitive apparatus replaced the compass needle of the earlier investigators could the effects be detected in relatively pure metal. The effect of cold-working in inducing ferromagnetism was rediscovered by Bitter8 in 1930 in a sample of impure copper, and this was confirmed by Lowance and Constant: Honda and Shimizu, l0,11 and others. In the same year, Tammann and Oelsen12 showed that copper-rich copper-iron alloys after certain heat-treatments could be rendered ferromagnetic or made more strongly ferromagnetic by cold-rolling. Kussman and Seeman13 showed that the change of susceptibility of relatively pure copper on cold-working was associated with the iron content, and concluded that actual precipitation of iron was caused by cold-working, which is a satisfactory theory until one considers the improbably high rate of diffusion that this would involve. When studying precipitation phenomena in

Jan 1, 1942

By M. E. Learmont, R. J. Lipp, I. Iwasaki

In the selective flocculation of iron ores, the concentration of alkaline earth ions in pulp solutions plays a critical role. Sodium silicate, alone or with sodium tripolyphosphate, has been used as a dispersant. When Ca+ + concentration exceeds 15 to 20 ppm, however, only a strong complexing agent, such as ethylenediaminetetraacetate (EDTA) was found to be effective (Heerema, Lipp, and Iwasaki, 1979). Some iron ores release Ca+ + in excess of 20 ppm. With ores that contain gypsum, the Ca+ + concentration may reach several hundred ppm. The purpose of this investigation was to compare the effectiveness of EDTA with nitrilotriacetate (NTA) in countering the adverse effects of Ca+ +, particularly at high Ca+ + concentrations. Emphasis was placed on the use of NTA since it is more cost-effective than EDTA. It is also used in detergents in some countries (Malaiyandi, Williams, and O'Grady, 1979). NTA, like EDTA, forms a soluble complex with Ca+ + with a 1:1 molar ratio. Its structure and the value of log Kca are given below together with EDTA (Shibata, 1963). [ ] For experimental materials, an equal weight mixture of Lac Jeannine hematite and a high-purity quartzite from Thompson, MN, both ground to - 30 µm (- 560 mesh) was used. Selective flocculation test conditions and procedures were identical to those used in previous investigations (Heerema, Lipp, and Iwasaki, 1979). The optimum level of starch addition for the above mixture was determined to be at 300 g/t (0.6 lb per st). Initially, a series of selective flocculation tests were performed on the mixture pulped with 10-3M CaC12 (40 ppm Ca + +) at pH 11. With no NTA present, flocculation of the entire suspension resulted. The selectivities achieved in tests with 90, 100, and 150% of the stoichiometric amount of NTA were virtually identical to each other and also to the selectivity of separation obtained in the absence of Ca+ + Such an observation could have been expected since Ca+ + concentrations up to a few ppm may be tolerated in selective flocculation (Krishnan and Iwasaki, 1982). A similar series of tests were performed at 10-2M CaC12 (400 ppm Ca+ +). The results are shown in Fig. 1 as grade¬recovery curves. For comparison, the results obtained in the absence of Ca++ are included. At 90% of the stoichiometric amount of NTA, a large enough concentration of uncomplexed Ca+ + was left in solution to cause indiscriminate flocculation. Note in this figure that NTA is capable of countering the adverse effect of Ca+ + even at this high concentration when it is used in excess of stoichiometric amounts. The free Ca+ + concentrations at 100 and 150% are calculated to be 2.5 and 0 ppm, respectively. [ ] The relative effectiveness of NTA and EDTA was then compared at 100% of the stoichiometric amount using 10-2M and 10-3M CaCI2 (Fig. 2). EDTA appears to be slightly more effective than NTA. The free Ca++ of 0.02 ppm in 10-2M CaC12 with EDTA compared to 2.5 ppm free Ca+ + with NTA might account for the difference. As evident, prohibitively high additions of EDTA and NTA were required to complex high concentrations of calcium ion. The use of both of these agents would result in the accumulation of complexed Ca+ + in recycle water.

Jan 1, 1985

By Herbert H. Kellogg

Graphs representing the standard free-energy of formation as a function of temperature for 21 fluorides are presented, along with estimated values for the standard free-energy of formation of 20 atedadditional fluorides. A few of the many possible uses of these data in metallurgical calculations are discussed, including the fluorination of oxides, sulphides, metallurgicaland chlorides, and the reduction of metal fluorides. RECENT papers which have presented free-energy data for oxides, sulphides, chlorides, carbonates, sulphates, and silicates in the form of free energy vs. temperature plots,1-5 have found important uses in teaching and metallurgical development work. This method of presentation of thermo-dynamic data serves to make available in readily usable form thermodynamic constants which are scattered throughout the literature, and to show by graphical means the stability relations which exist between the compounds of a given type. It is certainly desirable to have these free-energy-temperature diagrams for as many types of compounds as are of present or potential use in metallurgical processes. Thus, even though there are but few uses of metallic fluorides in extractive metallurgy today, the potential uses of fluorine processes are of great importance and serve as the principal justification of this paper. Recent developments in the production of fluoro-carbons have resulted in vastly improved methods for the production and handling of fluorine and corrosive fluorides, with consequent reduction in costs.".' The extractive metallurgist should no longer overlook possible fluorine processes when development of a new process for a relatively high unit-price metal is being considered. In a previous paperv he author outlined in some detail the importance and use of free-energy data in metallurgical calculations and also discussed the properties of a standard free-energy vs. temperature diagram. The same method of presentation is adopted in this paper, and the reader is referred to the earlier work for explanations of the use of free-energy data. Thermodynamic Data This paper presents standard free-energy vs. temperature diagrams, Figs. 1 and 2, for those fluorides for which the major thermodynamic constants are known. In the calculations of the standard free-energy of formation (AGO), values of the enthalpy of formation at 298°K (?Ho,) were taken from "Selected Values of Thermodynamic Constants"8 most of the values of standard entropy at 298°K (S°298) were taken from "Selected Values"," but in a few cases the values given by Kelley9 ere preferred; data for the Phase changes came from "selected Values" and several of Kellley's publics- tions;0-12 and most of the specific-heat data were taken from Kelley.l0 The appendix gives a detailed list of the sources of the data. As explained in an earlier paper,6 he accuracy of some of the standard free-energy relationships is not high. An error of +1 kcal at 1000°C is expected in most of the curves of Figs. 1 and 2. The error may be as high as +3 kcal in some of the curves. Rather than attempt to estimate the reliability of each curve, the source of the data used is reported in the appendix, and the reader may compare these data with newer values as they become available. Figs. 1 and 2 fail to show values for the fluorides of many important metals. In most cases this is because the entropy of the metallic fluoride is unknown. For preliminary calculations it is often useful to have available the best estimate of an unknown datum, rather than no information at all. With this in mind, Table I lists estimated standard free-energy values for a number of important metallic fluorides not included in Figs. 1 and 2. The values reported in Table I were, calculated by Brewer et al.13 and are based on estimated entropy values. The estimated uncertainty of the values for each fluoride were calculated from the uncertainty values given by Brewer1' for ?H°, and the entropy function.

Jan 1, 1952

By Cyril Stanley Smith

ON the 6th of February 1684, Dr. Martin Lister mentioned at a meeting of the Royal Society1 that "brass is magnetical," and promised to give an account of that assertion at some other time. He repeated his promise but never fulfilled it, and it was left for William Arderon2 to show, in 1958, that brass could be made magnetic by hammering and that it would retain polarity after magnetizing. Twenty-seven years later Cavallo3,4 examined the matter in great detail. Working with cast calamine brass, he showed that it could be made magnetic by hammering and nonmagnetic by subsequent annealing at a red heat. He found that annealing at a very high temperature caused the samples to lose their magnetic quality permanently, even after subsequent cold-working, but that remelting and cold-working restored it. He encountered some samples of brass that could not be rendered magnetic by any treatment. Experiments in which these were remelted with iron additions gave negative results, and Cavallo concluded that iron impurity was not the cause of the magnetism. He worked with 50-grain (3-gram) samples melted under the blowpipe, hence cooled very quickly. Bennet5 made whole crucible charges from copper and zinc, and found the resulting brass ingots to be magnetic only when iron had been added and then only after cold-working. All these observations applied to material in the cast condition, in which coring would produce a continuous spectrum of composition and cooling would result in varying degrees of precipitation. This knowledge of the subject seems to have been forgotten in the nineteenth century. The older brass was made by the calamine process and frequently contained iron in amounts of 0.5 per cent or more, absorbed from the impure ore with which the copper and charcoal were heated in making the brass. When metallic zinc became available in commercial quantities, calamine brass gradually disappeared, and with it the knowledge of its curious magnetic properties. Only when sensitive apparatus replaced the compass needle of the earlier investigators could the effects be detected in relatively pure metal. The effect of cold-working in inducing ferromagnetism was rediscovered by Bitters in 1930 in a sample of impure copper, and this was confirmed by Lowance and Constant,9 Honda and Shimizu, 10,11 and others. In the same year, Tammann and Oelsen12 showed that copper-rich copper-iron alloys after certain heat-treatments could be rendered ferromagnetic or made more strongly ferromagnetic by cold-rolling. Kussman and Seeman13 showed that the change of susceptibility of relatively pure copper on cold-working was associated with the iron content, and concluded that actual precipitation of iron was caused by cold-working, which is a satisfactory theory until one considers the improbably high rate of diffusion that this would involve. When studying precipitation phenomena in

Jan 1, 1941

By E. P. Abrahamson

The effect of transition element binary solid solution additions upon the re crystallization temperature of nickel has been investigated. All additions raised the re crystallization temperature. Both the rate of change of re crystallization temperature with at. pet solute and the limit of initial linearity are found to correlate with the free atom ground state outer electron configuration of the solute element. A comparison of all of the correlations for the transition elements studied has yielded a set of empirical relations, which allows the prediction of the effect of dilute binary transition elements on the recrystallization temperature of other transition elements. The work of Abrahamson, et al.1-7 on dilute binary solution alloys indicated a correlation between the free atom ground state electron configuration of the solute and both the brittle-ductile transition and re-crystallization temperature. Further, it has been shown3,4 that the limit of initial linearity may also be correlated with the solute electron configuration. Since previous studies have dealt with bee and hexagonal base elements, this study is made to note what effect, if any, the fee base structure might have. Nickel also serves to give a solvent configuration which will allow the comparison of all of the transition element solvents. Olsen8 has studied the effect of some trace elements upon the recrystallization of nickel. He included only Ti, Zr, W, Mn, and Co of the transition elements. The differences in change of recrystallization temperature were attributed to the solute atom size and to the solubility of the solute in nickel. PROCEDURE All alloys were made using 99.9 + pet Ni with 0.003 C, 0.015 Fe, 0.007 0, and 0.0007 H. The solute elements were 99.9 + pet pure. According to the published binary phase diagrams9 and metallo-graphic examinations at X750, all solute elements were in solid solution. The alloys were arc melted and remelted four times in the form of cubic 200-g buttons under an argon atmosphere. They were then hot forged at 800oC to 0.750 in. diam, machined to 0.60 in., vacuum annealed for 1 hr at 700°c, swaged to 0.40 in. and annealed at 700oC for 1 hr in vacuum. The grain size was checked and found to be 77 * 20 grains per sq mm. The specimens were then swaged to 0.187 in., yielding 76 ± 1 pet cold work. All alloys were then chemically analyzed for the solute addition. The interstitial contents remained at the values of the starting material when checked on random alloy specimens. The swaged rod was cut into 8.25 in. lengths and heat treated in a gradient furnace for 1 hr. The gradient was maintained at 250" to 850°C over an eight inch length, recorded by twelve thermocouples. Control was ± 3oC, accomplished at the hot end. The recrystallization was determined metallo-graphically over the entire specimen. The criterion chosen was that point on the specimen showing the first recrystallized grain at a constant magnification, X200. Specimens were repeated, and the agreement was found to be generally ± 3oC.

Jan 1, 1962

JUST as I have told you that it is impossible to give an exact rule for the bell scale, so I say the same concerning the clappers. Yet, if one wishes the bell to sound well, it is necessary that it have a proportioned blow; for if it is struck with a clapper that is lighter than it should be, it will not give out all the sound that it contains, and if it is struck with a heavier one than it can support, it is forced and the sound is made crude and harsh, in addition to the danger of breaking the bell. Therefore-the clappers must be made so that they bear a certain proportion to the bell, and in order not to proceed by chance, I have diligently tried to find the method as well as possible. I have found that experienced masters [99] have given to bells weighing ten pounds a clapper of one and a half pounds [and, to larger ones, clappers as tabulated on the next page].* Larger numbers than these I have not found because, in truth, few of the extraordinarily large ones are made in our regions. In my opinion, the masters should not be limited to these rules for the differences in clappers but should proceed according to the kind of bell, using a certain discretion for it is not possible to give a definite rule.

Jan 1, 1942

By D. H. Thompson, A. W. Tracy

Season-cracking is a type of failure of brass that results from the simultaneous effect of stress and certain corrodants. The object of this paper is to present data that will aid in a more complete understanding of the mechanism of season-cracking and related phenomena. Results presented show that certain high copper alloys are susceptible to season-cracking or stress-corrosion cracking, and possible explanations are discussed. Starting at least as far back as 1906, many papers have been devoted to this subject but the symposium1 held in Philadelphia in 1944 is the richest source of information. In order to study season-cracking, several of the many variables were held constant so as to learn the effects of others. Season-cracking is generally understood to refer to the corrosion cracking of brass having internal stresses;²,³ it is a special case of the general stress-corrosion cracking. Inasmuch as applied stresses are more readily produced and controlled, they were used exclusively in this research and the resulting phenomenon must he called stress-corrosion cracking.²,³ Only constant tensile stresses were used. The agents believed to be most frequently responsible for season-cracking are ammonia. amines and compounds containing then]. Both moisture and oxygen also appear to he necessary. Therefore, an atmosphere containing ammonia, water-vapor and air was selected for these tests. Briefly, the work consisted of exposing sheet metal specimens, having a reduced section ¼ by 0.050 in., of copper-base alloys to the effect of static tensile stresses between 5,000 and 20,000 psi and simultaneous contact with a. continuously renewed atmosphere containing 80 pct air, 16 pct ammonia and 4 pct water vapor at 35°C. The gas mixture and the speci- mens were maintained above the dew-point. The time-to-failure in minutes was the primary measure of results. In order to limit the experiment to finite time, it was considered that a specimen which had neither failed nor undergone microscopically detectable cracking in 40,000 min. (4 weeks) while under a stress of 10,000 psi or more could be considered immune to cracking. This is merely a convenient limit and is not to be considered proof of immunity. Supplementary tests in the absence of stress using weight loss or microscopical appearance as measures of attack were made. Apparatus The apparatus used in this research is shown in Fig 1. To facilitate the description it may conveniently be divided into six parts: stress-producing units, test chamber, gas train, electrical controls, timers and gas analysis device. A stress-producing unit is shown in an exploded view at the left in Fig 2. At the right is an assembled unit with a specimen in place in the lower portion; it is this part that remains in the ammonia atmosphere during a test. The upper part contains a spring, a central threaded rod, a large nut and necessary washers, pins, and so forth. Stress is produced in the specimen by screwing down the top nut against the spring, thus putting a tensile load on the central rod and so on the specimen. The wrench that turns the nut by extending through the upper cap, is seen at the upper right of the figure. The magnitude of the load is gauged by measuring from the pin that extends through the side of the tube, to a fixed point on the large flange. Measurement is made with a vernier beam caliper, shown at the right of the figure. The necessary spring compression to give a desired stress is calculated from the calibration curve of the spring and the dimensions of the specimen. The test chamber, center Fig 1, consists of a thermally insulated steel box 32 in. long by 10 in. high by 7 in. wide. A horizontal baffle reaching nearly to each end divides the chamber equally. Below this baffle are inlets for air and ammonia, a heating coil and a fan. Thus the gases are warmed and mixed in the lower level and flow past the specimens in the upper level. A thermo-regulator and thermometer project into the upper space. The top is pierced by 12 ports flanked by 3/8 in. threaded studs. A test starts when a port is opened and a unit containing a stressed specimen is thrust through it and bolted down against a neoprene gasket. The test chamber is held at 35°C. The gas train, right rear Fig 1, carries ammonia and air continuously to the test chamber. Tank ammonia passes through two reducing valves, a needle valve, a flow meter and into the test chamber. The air from either the plant compressor or a small laboratory compressor passes through wool towers and flow controls to the flow-meter. It then bubbles through water at 34°C and through a heated line to the test chamber. Electrical controls, left rear, Fig 1, provide rectifiers and mercury relays for the test-chamber and humidifier-heating-control circuits and outlets for

Jan 1, 1950

By J. J. Gilman

Zinc monocrystals, when compressed nearly parallel to their basal planes (within 20), deform in a new way; and certain deformation markings, called "-bands," are typical of this new mode. Characteristics of these bands are described. Mechanical behavior of low angle zinc monocrystals was investigated in some detail. Recrystallization did not occur upon annealing of banded specimens that were free of deformation twins. -Bands do not seem to be the result of nonbasal slip, but rather, a result of a microbuckling mechanism. u-Bands differ qualitatively and quantitatively from ortho kink bands. A dislocation model, consistent with some of the features of u-bands, is described. THE plastic deformation of zinc monocrystals with slip planes (0001) nearly parallel to the stress axis was studied in this investigation. In a previous investigation, it was shown that some low angle zinc crystals (those with slip planes making angles of more than about 2.5+1° with the compression axis), deform by ortho kinking while others (those with slip planes making angles of less than 2.5+1° with the compression axis) deform in a new way.' This new mode of deformation will be described in some detail here. Some of its striking features are: 1—it operates only for compressive stresses, 2—its temperature dependence is anomalous, and 3—it exhibits a new type of "yield-point" behavior. The mode of deformation to be discussed is not new in the sense that no previous evidence of its existence had been reported. The markings that it creates on the cleavage surfaces of zinc crystals have been described by several investigators.'" However, this is the first time that it has been made to operate under controlled conditions so that its response to mechanical variables, temperature, and aging treatments could be investigated and its geometry completely described. Apparently. Jillson' as well as Holden3 and Pratt" believed that the small bands they observed were simply small versions of ortho kink bands. In fact, two of these authors3,6 "alled the markings "micro kink bands." In spite of the precedence, it is felt that this term is not entirely suitable because these bands do not have the same genesis as kink bands, and they are qualitatively different in structure. As will be indicated by later discussion, the bands seem to be related to the tensile deformation bands observed in aluminum. The present author has chosen to call the bands "micro deformation bands," or simply ",ubands," and the deformation process, ''p-banding." Experimental Methods Crystals were grown from 99.999+ pct Zn obtained from the New Jersey Zinc Co. The details of the technique are given elsewhere." It should suffice to say that the crystals were seeded for orientation control, and precision pyrex tubes were used for molding them. About 40 crystals were used, yielding some 130 specimens. Fig. 1 illustrates the typical form of the specimens and shows how the orientation angles are defined. The crystal specimens were usually 1 3/4 in. long and about 150 mil in diameter. The angle between the slip or cleavage plane (0001) and the specimen axis is designated by xo, while a is the angle between the maximum slope of the (0001) plane and the nearest close-packed direction [1210], vary ing from 0°to 30°. The crystals were cut into specimens with a jeweler's saw and the ends were squared by filing (specimens held in V-block). Crystals of this orientation are stiff toward bending, so this procedure introduced only deformation localized at the ends. Then the specimens were polished either chemically in 50 pct HNO³ or electrolytically in 20 pct chromic acid. The mechanical tests were made with an Instron testing machine. This machine weighs by means of electric strain gages on elastic bars and is quite stiff, since the full-load deflection of its load cells is at most 0.002 in. Most of the testing was done at a

Jan 1, 1956

By B. C. Craft

Louisiana experienced deeper and increased drilling during 1934, resulting in the discovery of five new fields: Bosco, Acadia and St. Landry Parishes; Lake Hermitage, Plaquemines Parish; Roanoke, Jefferson Davis Parish; Gillis, Calcasieu Parish; and Four Isle, Terrebonnc Parish. New sands were discovered at New Iberia, Iberia Parish; Lake Washington, Plaquemines Parish; Sligo, Bossier Parish; and in the Rodessa gas field, Caddo Parish. Other miscellaneous events worthy of mention are the continued leasing of prospective oil and gas lands in North and South Louisiana, extensive geophysical work in the Gulf Coastal area, and increased interest in the development of flank production on piercement type domes, resulting in the acquisition of flank acreage and the leasing of several shallow domes in the Gulf Coast and Interior salt-dome areas. The total oil production for Louisiana during 1934 was 32,529,082 bbl., an increase of 6,929,280 bbl. over 1933. The total daily production at the end of the year from 2421 wells was 102,752 barrels. North Louisiana During the year, 144 oil wells and 68 gas wells were completed in North Louisiana as compared with 111 oil wells and 47 gas wells during 1933. The North Louisiana oil production was 9,274,050 bbl. as compared with 10,023,580 bbl. during 1933, a decline of 749,530 bbl. The normal decline in the old fields and especially in the Zwolle area was partly offset by increased production in the Converse field, Sabine Parish, and by acid treatment of wells in the Zwolle, Converse and Caddo fields. There were no new fields discovered during 1934. During the year R. W. Norton enlarged the boundaries and reserves of the Rodessa gas field. A series of gas-bearing sands, was discovered in J. B. French, No. 1-B, sec. 34, 23 N. 16 W., below the oolitic lime found at 5500 ft. in which formation all previous wells had been completed. The total depth of this well was 5825 ft. Subsequent drilling has resulted in

Jan 1, 1935

By David T. Peterson

Calcium metal was found to deoxidize thorizcm at 1000° to 1200° C. The reaction kinetics were determilled and related to the diffusion coefficients of oxygen in thorium. The solubility of oxygen in thorium, the minimum oxygen concentration, and the diffusion coefficient were determined from 1000° to 1200°C. This firocess results in the lowest oxygen concentrations zohich have been reported for thorium metal. FOR many years it has been known that calcium metal will reduce thorium oxide to thorium metal. This reaction has been the basis for several methods of preparing thorium metal. From the equations giv-by Kubaschewski and vans, ' AF" for the reaction Cao, + Tho,(,) - CaO(,, + Th(,) was calculated and found to be -3.4 kcal at 1000°C, -2.5 kcal at llOO°C, and -2.0 kcal at 1200°c. Thorium is very slightly soluble in liquid calcium, and the solubility of calcium in solid thorium is very low. Consequently these metals would be in essentially their reference states. If thorium containing oxygen were equilibrated with liquid calcium between 1000° and 1200°C, the oxygen content of the thorium would have to be below the solubility limit in thorium. Oxygen is one of the impurities most difficult to remove from thorium and is the most abundant impurity in metal prepared by almost all known methods. Fortunately, oxygen does not have a large influence on the properties of thorium because the solubility in solid thorium is very low. EvenT in thorium containing 100 ppm of 0, particles of thorium oxide can be observed in the microstructure. In view of the incompatibility of thorium oxide and liquid calcium and the low solubility of thorium oxide in thorium, the deoxidation of thorium by this method was investigated. For thorium containing an amount of oxygen well in excess of the solubility limit, the reaction should proceed in the following sequence. The oxygen content of the thorium matrix near the surface would be depleted by the diffusion of oxygen to the surface. At the surface, the oxygen would react with calcium to form calcium oxide. To maintain equilibrium within the thorium, thorium oxide would dissolve to keep the matrix saturated. Consequently, the thorium-oxide particles would disappear first at the surface and then the particle-free rim would grow in thickness. If the rate-controlling step were the diffusion of oxygen through this layer of thorium which was growing in thickness in direct proportion to the amount of oxygen removed, the well known parabolic time law should be observed. If the oxygen concentration at the surface of the thorium and at the inner surface of the deoxidized rim were known, the diffusion coefficient of oxygen in thorium could be calculated from the parabolic rate constant. EXPERIMENTAL PROCEDURE The thorium metal used in this study was prepared by calcium reduction of ThF, by the method described by Wilhelm.' The analysis of this metal is given in Table I. The carbon was determined by combustion, the oxygen by the HC1-insoluble residue method, nitrogen by the Kjeldahl method, and the other elements by emission spectroscopy. A section of this ingot was hot rolled at 600°C to 1/4 and 1/8-in. thick plates. Specimens approximately 7/8 in. square were cut from these plates, and all surfaces of the specimens were cleaned and smoothed by filing with a clean file. Individual specimens were placed in 1-in. diam by 2-in.-long tantalum capsules. Approximately 1 g of clean, high-purity calcium was placed in the capsules and an end closure arc-welded in place. The tantalum capsules were sealed in Inconel crucibles to protect the reactive metals from oxidation. The entire loading procedure was done in a glove box filled with pure argon. The loaded crucibles were placed in a muffle furnace, controlled within 2OC of the desired temperature, for a measured length of time. After the specimen had cooled to room temperature, it was sectioned perpendicular to the large faces and through the mid-point of two of the sides. The sectioned specimen was mounted and polished through Linde A abrasive. The rim which was free of thorium-oxide particles could be clearly observed microscopically as mechanically polished. Twenty measurements of the thickness of the rim were made at equally spaced points far enough from the end of the

Jan 1, 1962

By Robert B. Hall, Charles W. Bauer

Alunite, KA13(SO4)2(OH)6, was used from the 15th century until early in the present century as a source of potash alum and aluminum sulfate. Since early in this century its use for this purpose has declined to virtually nil with acid treatment of bauxite or clay replacing alunite as a source of alum. During the First World War alunite served as an emergency source of potassium sulfate fertilizer in the United States and Australia. More recently, alunite has been investigated as a nonbauxite ore of aluminum, with potassium sulfate and sulfuric acid as recoverable byproducts. The Soviet Union established a commercial-scale plant in the mid-1960s producing cell-grade alumina from alunitic ore and recovering byproduct potassium sulfate and sulfuric acid. Interest in nonbauxite ores, including alunite, is expected to continue in countries that presently are dependent on imports of bauxite or alumina to support their aluminum industries. The US has the largest aluminum producing and fabricating industry in the world but imports more than 90% of its aluminum-bearing raw materials. This chapter reviews the status of alunite as a potential source of aluminum with byproduct fertilizer, and the resources available to support this industry, whenever this becomes economically feasible. Historical Background Alunite has received little attention until recently, yet for centuries it held a higher place than many of the industrial minerals considered essential today. The deposits of alunite at Tolfa, northwest of Rome, were mined almost continuously from 1462 until about the middle of the present century (DeLaunay, 1907; Lombardi, 1977). The potash alum made from the alunite, called Roman alum, was a valued commodity in international trade, being used in the making of paper, in tanning leather, and as a mordant in textile dyeing. The industry at Tolfa is said to have been controlled by the Vatican and was a source of revenue for the Papal State until fairly recent times (Lombardi et al., 1977). Since early in the present century, the preferred method for making alum has been by acid treatment of bauxite, clay, or other aluminous material, so that alunite has fallen into near-total disuse as a source of alum chemicals. Appreciable quantities of mixed alunite-kaolin rock still are quarried in the Tolfa district for use by the Italian cement industry (Lombardi and Mattias, 1979), but the role of this material in the making of Italian cement is not clear. A large deposit of alunite-bearing rock in Chekiang province, mainland China, is said to have yielded a "great quantity" of alum over a period of several centuries (Yih, 1931). During the 19th century, alunite deposits in France, Spain, Australia, and other countries were exploited as raw material for making potash alum and aluminum sulfate. Interest in alunite was revived during the First World War, not for alum, but as an emergency source of potassium sulfate fertilizer. Large veins of nearly pure alunite had just been discovered on Alunite Ridge, 11 km southwest of Marysvale in Piute County, Utah (Butler and Gale, 1912), and these were quickly brought into production for making potash fertilizer to replace supplies cut off from the famous deposits at Stassfurt, Germany. An estimated 225 kt of Marysvale alunite was mined and processed at that time (Callaghan, 1973). Similarly, Australian alunite deposits were mined as a source of potash fertilizer during both world wars (Hall, 1978).

Jan 1, 1983

By Carlton D. Hulin

The usual concurrence in time and space of intrusive igneous activity, favorable structural disturbance and mineralization, which is so manifest in the mineralized district necessarily indicates a close interrelationship between these events. Evaluation of available evidence leads to the recognition that an appreciable time interval exists between the emplacement of the igneous intrusive and the formation of associated ore deposits. During this interval known portions of the intrusive are completely solidified, highly differentiated magma facies are injected as dikes, and important faulting occurs, which may fracture and shatter the solidified intrusive body. The highly differentiated dike types could only have originated in some deep portion of an underlying plutonic body that had reached an advanced stage of magmatic differentiation. Appearing after these dikes, the mineralizing solutions may likewise be presumed to have originated at great depth. Certainly no source for these solutions can be found in near-by portions of the intrusive igneous body. The association of igneous intrusives and clustering ore deposits must be recognized as resulting from structural control. The emplacemerit and the subsequent solidification and cooling of the intrusive set in operation forces that are responsible for the favorable structural disturbances that control the mineralized district. The emplacement of the body of fluid magma weakens the crustal rocks to the extent that failure due to strains originally present in the rock body may occur. Faulting of any type and of any magnitude may be the result. Subsequently, owing to the change of state from fluid magma to crystalline granitic rock, volume decreases approximating 10 Per cent may Occur, with resultant shrinkage and collapse within the rock body. Following solidification, thermal contraction, induced by cooling of the rock body, causes a further volume reduction of 6 per cent. This thermal contraction, extending over a lengthy period of time, results in a succession of minor fault movements. These small fault movements, occurring progressively throughout the period of mineralization, are responsible for maintaining the permeability of the rock body, without which access of the mineralizing solutions and the formation of the ore deposits of the mineralized district would be impossible. Introduction A proper understanding of the causes that have localized our mineralized districts should be of considerable value to geologist and engineer alike. under current conditions the known ore reserves of productive mining camps are being rapidly depleted. Although ore of the future will be derived in part from deposits now known and from Ore bodies that are still to be discovered within the limits of productive mining districts, in part at least it must come from mineralized districts whose existence or importance yet remain to be recognized. The mining geologist is thus faced with two problems of paramount importance: (I) the location of new ore bodies within known mineralized areas and (2) the location of new mineralized districts within whose confines, previously unknown, valuable Ore deposits may occur. Any contribution to our knowledge concerning the causes for the localization of mineralized districts

Jan 1, 1949

By Carlton D. Hulin

The usual concurrence in time and space of intrusive igneous activity, favorable structural disturbance and mineralization, which is so manifest in the mineralized district necessarily indicates a close interrelationship between these events. Evaluation of available evidence leads to the recognition that an appreciable time interval exists between the emplacement of the igneous intrusive and the formation of associated ore deposits. During this interval known portions of the intrusive are completely solidified, highly differentiated magma facies are injected as dikes, and important faulting occurs, which may fracture and shatter the solidified intrusive body. The highly differentiated dike types could only have originated in some deep portion of an underlying plutonic body that had reached an advanced stage of magmatic differentiation. Appearing after these dikes, the mineralizing solutions may likewise be presumed to have originated at great depth. Certainly no source for these solutions can be found in near-by portions of the intrusive igneous body. The association of igneous intrusives and clustering ore deposits must be recognized as resulting from structural control. The emplacemerit and the subsequent solidification and cooling of the intrusive set in operation forces that are responsible for the favorable structural disturbances that control the mineralized district. The emplacement of the body of fluid magma weakens the crustal rocks to the extent that failure due to strains originally present in the rock body may occur. Faulting of any type and of any magnitude may be the result. Subsequently, owing to the change of state from fluid magma to crystalline granitic rock, volume decreases approximating 10 Per cent may Occur, with resultant shrinkage and collapse within the rock body. Following solidification, thermal contraction, induced by cooling of the rock body, causes a further volume reduction of 6 per cent. This thermal contraction, extending over a lengthy period of time, results in a succession of minor fault movements. These small fault movements, occurring progressively throughout the period of mineralization, are responsible for maintaining the permeability of the rock body, without which access of the mineralizing solutions and the formation of the ore deposits of the mineralized district would be impossible. Introduction A proper understanding of the causes that have localized our mineralized districts should be of considerable value to geologist and engineer alike. under current conditions the known ore reserves of productive mining camps are being rapidly depleted. Although ore of the future will be derived in part from deposits now known and from Ore bodies that are still to be discovered within the limits of productive mining districts, in part at least it must come from mineralized districts whose existence or importance yet remain to be recognized. The mining geologist is thus faced with two problems of paramount importance: (I) the location of new ore bodies within known mineralized areas and (2) the location of new mineralized districts within whose confines, previously unknown, valuable Ore deposits may occur. Any contribution to our knowledge concerning the causes for the localization of mineralized districts

Jan 1, 1949

By K. E. Manchester, A. H. Clark

Hall measurements have been made on three groups of silicon samples, which were implanted with boron, aluininunz, and phosphorus ions. Boron and phosphorus implants show essentially bulk properties when annealed under previously determined conditions, i.e., 15 min at 80O°C for boron and 10 mirz at 600°C for phosphorus. Bulk properties were also observed in alu?rrilzum-implanted samples when ion concentrations were below 1015 cm-'; however, strange low- terrzperalure behavior and a falloff in cavrier concenlralion was observed for sarnples with ion concenlration abozle loL5 ern-'. This can be attributed to solid-solubility effects since the average bulk concentration f0.r the sample exhibiting bulk properties was below the reported solubility limit for aluminum, while the other samples were above the limit. A detailed study of the annealirzg process indicates that mobilities reach bulk c~alues in phosphorus implants at 250DC, in alutninurn ivnplanls a1 500°C, and in boron implants at 700°C. A simple rnodel has been proposed to fit the annealing data. THE technique of semiconductor doping by direct injection of energetic ions is being actively investigated at this Center. Previously published results from this laboratory have been concerned with the investigation of implanted profiles in silicon and the electrical properties of the resultant p-n structures.1'2 Diode properties have been reported for junctions produced by implantation of boron ions and aluminum ions in n-type silicon and phosphorus ions in p-type silicon. Reverse current characteristics, as well as electron diffraction data, have indicated that the damage to the structure produced by the energetic ions during the stopping process can be minimized by a gentle anneal. The time-temperature conditions for this process have been determined by sheet resistivity studies.3 Electrical profiles of implanted phosphorus ions which have been determined by a differential sheet conductivity technique are based on the assumption that the carrier mobilities and activation energies for ionization are the same as in bulk silicon. These assumptions have been substantiated experimentally by measurement of Hall constants and resistivities of these implanted structures and the results are presented herein. After establishing the bulk property equivalence of the annealed layers, a more detailed examination of the annealing process was undertaken. The sheet resistivity technique initially used to determine anneal conditions has been broadened to include Hall constants and mobility behavior with anneal conditions. PROCEDURE The three groups of samples prepared for Hall measurements were implanted with mass-separated beams of boron, aluminum, and phosphorus ions. Ion concentrations are equivalent surface concentration and they have been determined from beam current measurements during implantation. Implant conditions for the samples are shown in Table I. In all cases, the samples had previously been angle-lapped on one edge and the junction delineated with an HF-copper sulfate solution. The surfaces of the implanted regions of the samples were exposed to the delineating solution and in the case of the "n"-type phosphorus-implanted areas it was later discovered that a finite amount of surface could be etched by this solution. This is discussed in the section on results. The implanted samples were ultrasonically cut into the conventional six-probe configuration shown in Fig. l.* In the annealing studies, for which the meas- urements were taken at room temperature, the sample holder was a Bakelite jig incorporating tungsten mechanical probes. The other measurements were taken using a conventional liquid-nitrogen cryostat, in which the temperature could be varied from 77" to about 400°K. For these measurements, 10-mil aluminum dots were evaporated onto the samples and alloyed with the silicon at 530°C for 15 min. The samples were then mounted in flat-packs, and gold wires were bonded to the aluminum dots. The electrical measurements were made with either a Leeds & Northrup K-5 Potentiometer, a Keithley 147 Nanovolt Null Detector, or a Keithley 601 Electrometer. No external bias was applied to the substrate. There is an inherent self-biasing arrangement at one or the other of the current contacts (depending upon the polarity), and this suffices to limit the current flow to the implanted layer. The magnetic field was generated by an A. D. Little electromagnet. Except for occasional checks of linearity of the Hall voltage with

Jan 1, 1969

By E. P. Dahlberg, R. E. Reed-Hill

On the assumption that stress or strain relaxation occurs as the result of a thermally activated process, equations are derived relating to tensile experiments that give the strain as a function of the time under the condition of constant stress, and the stress as a function of the time for constant strain. It is demonstrated that if the strain-rate equation i = previously proPosed by Kuhlmann., is used as a starting point, then the relaxation of strain at constant stress may be expressed by the equation c = (-RT/(Y) 1tz tanh (t + is the strain capable of being relaxed at any given instant. Similarly, it is shown that the relaxation of stress at constant strain may be given by a = (-RT/B) In tanh (t + t0)/27, where a is the instantaneois value of the relaxable stress. The fact that these relationships reduce to well-known empirical equations at both large and small values of the stress Or strain is also shozcn. The present theory is shown to agree well with experimental data obtained from tensile elastic aftereffect experiments on a zirconium specimen prestrained at 77 k as to make it strongly anelastic. It is also demonstrated that elastic aftereffect data obtained using torsional specimens ?,Lay agree reasonably well with the equation derived for the case of tension. RELAXATION experiments are often employed as a means of studying metallic deformation mechanisms.' The simplest and most commonly employed techniques involve stress relaxation at constant strain and strain relaxation at constant stress. In general, however, investigations of this nature have been seriously handicapped in the past by a lack of suitable equations giving the time dependence of the relaxing variable over an interval that extends from small strains up into the region where internal-friction experiments become strain-amplitude dependent. This paper presents a derivation of such a set of equations for the case where the time-dependent part of the strain is anelastic or recoverable and the specimens are loaded in simple tension. The relaxation of strain under the condition of constant stress will be considered first. Let us assume that strain relaxation occurs as the result of a reversible thermally activated process that occurs at a number of relaxation centers lying in an elastic matrix. Then, following Kuhlmann,2 we may express the rate of strain relaxation as follows: where C is the strain rate, AFx the free energy of activation of the process controlling strain relaxation, a, the effective or average resolved stress at the relaxation centers, u an activation volume, R the universal gas constant, T the absolute temperature, > a factor with dimensions of a volume that accounts for the strain contribution of a successful operation of a unit process, N the number of relaxation centers per unit volume, and v the Debye frequency. The first term on the right of Eq. [I] represents a strain rate in the direction favored by the stress, while the second term represents the rate in the opposite direction. It is implied in Eq. [I.] that both F and v are symmetrical with respect to the two basic directions of operation of a relaxation process. Eq. [I] may also be written where and S and Q are the activation entropy and activation energy, respectively, of the relaxation process. In the following, A will be considered a constant. This is compatible with a set of experimental conditions where the relaxation rate is controlled by a single basic reversible process in which it may be assumed that the temperature dependence of the product ?Nv is negligible in comparison with the temperature variation of the exponential term. It is also implied that v, 7, and N do not depend strongly on a, . In deriving a relationship for the strain as a function of the time from her equation, equivalent to Eq. [2], Kuhlmann2 chose to consider only the limiting cases where the time was either very small or very large. It will now be shown that it is possible to integrate Eq. [2] to obtain a single equation valid over a wide range of strains if the concept of relaxable strain is introduced. The use of this quantity, which is the difference between the instantaneous value of the strain and the value of the strain at complete relaxation, represents the primary point of departure of the present theory from that of earlier workers. Let us express the effective stress at the relaxation centers in terms of strain. For this purpose we may use the following equation derived by zener3 for the case of strain relaxation at slip bands: where M? and M are the relaxed and unrelaxed moduli respectively, go the applied constant tensile stress, and m an average orientation factor that takes account of the fact that a,, the effective stress at the relaxation center, may not be a tensile stress (i.e., a

Jan 1, 1967

By B. B. Rath, Hsun Hu

In wedge-shaped bicrystals of zone-refined aluminum it is observed that (111) pure tilt boundaries migrate under the driving force of their own inter-facial free energy. The boundary velocity is a power function of the driving force. The driving force exponent decreases with decreasing angle of misorien-tation. For example, at 64O°C, the exponent decreased from 4.0 for a 40 deg to 3.2 for a 16 deg tilt boundary. An evaluation of the driving force acting on the boundaries during their motion indicates that for low driv-forces, up to about 2 x l03 ergs per cu cm, the velocity is relatively independent of misorientation, whereas at higher driving forces a 40 deg tilt boundary exhibits the highest velocity. The measured activation energy for boundary migration approaches that for bulk self-diffusion at low driving forces, decreasing from 33 to 27 kcal per mole as the driving force is increased from 1 x l0 to 5 x l03 ergs per cu cm. These results are compared with current theories of grain-boundary migration. In previous experimental studies of grain boundary migration the driving force has been limited to a difference in stored energy across the boundary. This stored energy has been introduced into the crystal either by prior deformation1-3 or by grown-in lineage structure. A part of the energy stored in the deformed crystal is released by recovery either prior to or concurrently with grain boundary migration, thus introducing an uncertainty as to the magnitude of the driving force responsible for grain boundary migration. The grown-in lineage structure, though thermally stable during annealing, neither provides conditions under which different levels of energy may be stored in the imperfect crystal nor provides a control of orientation difference across the migrating boundary of a growing grain. Furthermore, because of variation in the lineage structure, it is difficult to determine accurately the energy stored in the imperfect crystal. Several investigations of grain boundary migration during normal grain growth have also suffered from difficulties in estimating the driving force because of uncertainties in the principal radii of curvature.~ In the present investigation the velocity of pure tilt boundaries in zone-refined aluminum bicrystals of selected orientation (40, 30, and 16 deg around the [Ill] tilt axis) has been measured in the absence of a dislocation density difference across the moving boundary, thus eliminating the previous experimental difficulties. The driving force for boundary migration is derived from a gradient of the total interfacial free energy of the migrating boundary in wedge-shaped bicrystals. A similar method was attempted by Bron and Machlin in a study of grain boundary migration in silver. However, they found that one of the crystals was deformed and consequently the motion of the boundary was partly due to a difference of stored energy across the boundary. The observed behavior of boundary velocities as affected by the driving force is examined in the light of the predictions of the current theories of grain boundary migration.7"10 The effect of boundary misorientation on velocity is compared with the theory of " which is based on a dislocation core model for high-angle boundaries. EXPERIMENTAL METHOD Seed-oriented bicrystals of zone-refined aluminum, 2.5 cm wide, 0.5 cm thick, and 12 cm long, containing tilt boundaries with a common (111) axis, were grown from the melt in the direction of this axis. Spectro-graphic analysis, reported earlier,'' indicated the purity of the crystals to be 99.999+pct. Three such bicrystals containing 16, 30, and 40 deg tilt boundaries were used. Wedge-shaped specimens were prepared from these bicrystals by spark cutting followed by electrolytic polishing. The angle of the wedge was usually 40 deg and the specimens were usually 0.25 cm thick. The intercrystalline boundary was located within 0.2 to 0.5 cm from the tip of the wedge. Fig. 1 shows a section of an oriented bicrystal containing an outline of a wedge-shaped specimen. The crystallographic directions shown in Fig. 1 represent the orientation of one of the crystals (the larger section of the bicrys-tal); the orientation of the other crystal differs only by rotation around the common [lil] axis. The parallel faces of the wedge always corresponded to the common (171) planes in both crystals, whereas the orientation of the side faces varied, depending on the misorientation angle. The bicrystal orientations were determined

Jan 1, 1970

By T. M. Geffen, J. L. Sanderlin, F. F. Craig, D. W. Moore

Scaled reservoir models have been used to study the effect of gravity on oil recovery performance in frontal-drive operations; namely, water, gas, or solvent flooding. The difference in density between the reservoir oil and the injected fluid causes their segregation, resulting in a non-uniform advance of the fluid front. In the laboratory flow tests, which simulated both five-spot and linear injection operations in flat reservoirs, the viscous, capillary, and gravity forces present in these operations were scaled. Dyed fluids were used so that the gross movement of the injected fluid could be observed. The studies covered a range of injection rates, formation thicknesses, and rock and fluid properties normally encountered in field operations. The results of the model tests indicate that the volume of the reservoir contacted by the injected fluid at its breakthrough into the producing well is less than that expected based on information which neglects gravity effects. This difference can often be as much as 80 per cent by gas or water injection in uniform sand bodies. Preliminary flow tests on a non-uniform sand body indicate that the uniformity of the flood fronts may in some situations be influenced to a much greater degree by permeability variations within the rock body than by gravity effects. The magnitude of fluid segregation due to gravity is controlled by the average injection rate, rather than day to day or week to week variations. INTRODUCTION One of the important factors controlling the oil recovery from a frontal-drive operation, such as water, gas, or solvent injection, is the volumetric sweep efficiency. This factor is a measure of the gross portion of the reservoir that is contacted by the displacing fluid. The volumetric sweep efficiency is influenced by gravity effects, well arrangements, and variations in rock permeability within the reservoir. The gravity effects are due to the displacing fluid being of different density than the reservoir oil. This causes the displacing fluid to move preferentially toward either the top or bottom of the formation. Non-uniform advance of the flood front can be caused by the relative positions of the injection and production wells. Variations in rock permeability also result in an uneven advance of the displacing fluid. Gas zones, representing paths of low resistance, may result in non-uniform movement of the injected fluid. The more uneven the advance of the displacing fluid, the lower is the volumetric sweep efficiency and thus the lower the oil recovery efficiency. The effects of well arrangement and permeability variations, upon the gross movement of the injected fluid have been the subjects of extensive investiga-ti0ns.1,2,3,4,5,6 Gravity effects have been recognized as being present in frontal-drive operations'.' but there has been little quantitative measure of their magnitude. Very likely the reason gravity effects have not been studied is that this problem does not lend itself to simple experimental or mathematical analysis. The development of reservoir modeling techniques has made possible a quantitative determination of the effect of gravity on fluid segregation and thus upon the oil recovery performance of frontal-drive operations. This paper presents a progress report on a laboratory investigation of gravity effects in fully liquid-saturated, horizontal, uniform as well as non-uniform systems. These results were obtained from scaled experiments on both linear and five-spot systems within the range of conditions normally encountered in secondary recovery operations. This study is concerned with the gross movement of the injected fluid to the time it first reaches the production wellbore. Therefore, it should be emphasized that the results of this paper can not be used to determine the effect of gravity segregation on oil recovery efficiency at abandonment conditions. MODEL SCALING The science of scaling models is relatively new as applied as petroleum production problems, Many of the scaling techniques have been adaptions of those used in basic studies of heat and fluid flow. There are

Jan 1, 1958