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By Gareth Thomas

The analysis of Kikuchi pattersns of exct ovientalions from single cryslals and paired Kikuchi lines from single and overlapping crystals is shown to be useful and quanlitalve and is applied to Phase transfovnzcitions including ordering, spinodals, mavten-silic, and nuclealion and growth pyocesses. 112 pinciple, the analysis of exacl orientations enables the crystal system and the Bravais lattice of a crystal to he determined. The advantages of the davk-field imaging technigure for detecting vevy small precipitates are also described. ALTHOUGH Kikuchi electron-diffraction patterns were first observed nearly 40 years ago,' little systematic application seems to have been made of them, until fairly recently during electron microscopy, when their usefulness in contrast experimen and for determining exact orientations8'9 has been pointed out. With the availability of gonio-metric specimen tilting stages it has now become possible to make much wider use of diffraction patterns, particularly the Kikuchi pattern, which is the main subject of this paper. The treatment presented here is not exhaustive but it is hoped that it will stimulate more use of Kikuchi patterns during electron-microscopy investigations. The Kikuchi pattern is formed as a result of Bragg diffraction of the inelastically scattered electrons produced during the interaction of the beam and thick specimens, The important feature of these patterns is that they give an accurate representation of the symmetry of the crystal being investigated, so that it is possible to identify crystal systems and even the Bravais lattice. This means that new structures, e.g., formed in phase transformations, may be identified during normal electron microscopy, so that Kikuchi-pattern analyses considerably extend the uses of the electron microscope. Recent work has also shown that dark-field images are more informative than bright-field images, particularly, for observing small precipitates. The second part of this paper discusses some applications and advantages of dark-field imaging in studies of two-phase systems. 1) DIFFRACTION PATTERNS 1.1) Spot Patterns. Electron-diffraction spot patterns have their limitations because of the importance of the form factor on the intensities and shape of the reciprocal lattice points. Because of the extension of these points into relrods, reflections are possible over a large angular range (+5 deg) and the patterns from thin regions can be complicated because second-layer relrods intersect the reflecting sphere. Spot patterns can thus give only an approximate idea of the crystallography unless the foil is tilted into exact orientation. In this case the spot pattern is symmetrical, with equal numbers of spots on the positive and negative zone directions about the origin. Such cases are necessary for structural analyses and have been used recently to determine the crystal structure of the ordered Ta64C phase." Exact orientation means that the plane of the reciprocal lattice lies exactly normal to the incident beam as shown in Fig. 1(b). It should be noted that in exact orientations the angle of reflection is less than the exact Bragg angle 9 so that the reciprocal lattice points lie to the outside of the sphere, Fig. 1(b). This deviation is denoted by the parameter s and in the usual convention4 s is negative for exact orientations and, of course, zero at the exact reflecting position shown in Fig. l(a). In order to avoid secondary reflections from thickness relrods it is advantageous to work in thicker regions of foils. Diffraction from thick regions may also produce Kikuchi patterns and as dis-

Jan 1, 1965

By Chikaosa Tanimoto

INTRODUCTION The committee on Rock Mechanics, Japanese Society for Civil Engineers, has been discussing 'soft rock engineering in Japan' and presented several papers concerning dam, tunnel, bridge and slope constructions to International Symposium on Weak Rock, Tokyo 1981. This is the summarized paper based on References of Okamoto et a1 (1981), Iida et a1 (1981), Working Group on Tunneling-JSCE (1981), Working Group on Bridge Foundations-JSCE (1951) and Kikuchi et a1 (1981), which can convey general view on engineering experiences with weak rocks in Japan. From the point of view to the origin and/or distinctive physical properties, weak rocks in Japan may be classified into (1) sedimentary, (2) weathered, (3) low welded-pyroclastic and (4) fractured ones. Their typical characteristics are summarized in the following section. Concerning dam foundations on soft rock, several hundreds have already been constructed and, at present, nearly one hundred are under construction or at planning stage. These dams, almost without exception, have some problems such as site selection, material selection for fill-type and concrete dams, design of dam and its foundation, and construction procedures, requiring special ingeneous and cautious measures to cope with the local geotechnical difficult situations. In tunneling, for the decade of 1970s, the number of tunnels in soft rock either completed or under construction was at least 160, including Seikan Tunnel of 53.9 km long, Nakayama Tunnel of 14.8 km long and so on. Most of these tunnels are distributed in the northern half of Mainland, consisting of a basement of Paleozoic strata and Plutonic rocks, overlayed by Neogene Tertiary formations which include large

Jan 1, 1982

By Charles E. Glass

The stabil ity of engineered embankments subjected to earthquakes has received considerable attention in the last 10 years, but most of the effort has been directed toward stability of earth dams. Based upon past performance, earthquake- induced failures on non-impounding mine waste structures will likely correspond to small, local slumps or debris slides, and their stability should be considered as an integral part of mine economic planning. As such, stability considerations should include earthquake hazard, characteristics of earthquake ground motion, dynamic slope stability, and the impact that waste-dump failures have on mine operations. Numerous techniques have been proposed for analyzing the stability of embankments subjected to earthquakes. Before choosing an analysis technique, it is worth noting two important differences between the dynamic response of waste embankments and natural slopes. First, waste embankments respond as structures having unique modes of vibration, which causes embankment motions to differ from nearby ground motion. Second, because of embankment response, accelerations can be different at embankment crests than elsewhere in the structure and occur at frequencies that do not correspond to input ground motion. Because of these factors, embankment response should be calculated prior to slope stability assessment. In this paper several analysis techniques designed to calculate slope stability are evaluated, and conventional pseudostatic techniques are shown to be inappropriate for dynamic considerations. Techniques to calculate dynamic stability should include embankment response, all characteristics of earthquake motion, and roughness along failure planes as input, and should provide a displacement time-history of the slide mass as output. Two techniques satisfy this criterion, and in this paper the LADRS technique is recommended for its versatility and simplicity.

Jan 1, 1985

The Industrial Board of the Department of Commerce has been formed under the chairmanship of George N. Peek, formerly vice-chairman of the War Industries Board. This Board is to put into practical effect a program for the readjustment of prices for basic materials in such a fashion as to create a firm foundation on which the consumer can base his future purchases, and the producer can form necessary estimates. It has the assistance of the Council of National Defense. One of the first steps off the Board was to call into conference the leaders of industry. At these conferences the general conditions of the country are carefully considered and an effort made to determine and understand the principles that should be applied to permit the successful solution of the problem. It will be the endeavor of the Board to act promptly by consulting and interchanging views with these representatives of industry in the fullest and freest manner possible with a view to aiding and assisting industry in general to resume activities to the fullest practicable extent.

Jan 4, 1919

By E. J. Rapperport, J. P. Pemsler

We have made calculations to evaluate the sensitivity of atomic absorption as a technique to measure vapor pressure changes with temperature. Our conclusion, supported by the experimental findings presented in this work, is that the ultimate sensitivity of the technique is well below lo-' Torr. This magnitude of vapor pressure sensitivity makes the method extremely attractive for thermodynamic studies. Atomic absorption techniques have been used previously in this connection by Scatchard and Boyd' and by vidale2 with a much lower sensitivity reported. Scatchard and Boyd's work measured cadmium pressure over Ag-Cd alloys in the range 0.02 to 0.3 Torr, and Vidale estimated that sensitivities of only 10"5 to 10"6 Torr are to be expected. Atomic absorption appears to be particularly well-suited to thermodynamic studies for several reasons: A) It is extremely sensitive; our experiments indicate an ability to measure vapor pressure changes of 10"9 Torr. B) It is highly selective; there is seldom interference among the resonant wavelengths of the various species. C) It may be performed in an absorption cell under static conditions. This alleviates such problems as surface impoverishment of alloys, attainment of equilibrium, and temperature measurement and control. D) Simultaneous, or near-simultaneous, vapor pressure measurements may be made for several elements in a given system. Experimental. The physical basis of the technique is the highly selective absorption of particular wavelengths by specific atomic species. In most atomic absorption work the element of interest is incorporated into a hollow cathode lamp to provide a characteristic spectral source of high intensity. The spectra lines characteristic of the element in the cathode are attenuated by atoms of that element in the radiation path. Radiation from silver or cadmium hollow cathode lamps was directed along a path containing a 10-cm evacuated silica cell. The cell was positioned within a silica windowed furnace and contained silver, cadmium, or an Ag-Cd alloy. As the furnace temperature was elevated, the number of atoms of the absorbing element in the vapor phase within the cell rose, and the resonant radiation was increasingly absorbed. Intensities were measured by passing the radiation through a Techtron Model AA-4 one-half meter grating atomic absorption spectrometer equipped with a photo-multiplier detector. In order to minimize instabilities in the source, the hollow cathodes were allowed to warm up for several hours and were run at only 2 5 to 30 pct of their maximum rated amperage. In addition the attenuated beam was monitored before and after each reading. The attenuation of resonant wavelengths may be related to vapor pressure by the following relationships.

Jan 1, 1969

By Carl G. Hogberg

DURING recent months, the acute shortage of steel scrap has necessitated the use of higher percentages of hot metal in the open-hearth charge. With these higher percentages, the sulphur content of hot metal has become an increasingly important factor in the control of the quality of steel. Thus, the blast-furnace operator is faced with a demand not only for more output but for a higher quality of product. More than go per cent of the sulphur charged into the blast furnace is contained in the coke. With the tremendously increased demand, the trend of coke quality has been toward higher sulphur, higher and more variable ash, and poorer physical characteristics. This has been brought about by less selective coal mining, increased production rates in coke plants and resumption of operations of many beehive ovens. In a single month last year, one blast-furnace plant in the Pittsburgh district operated with coke obtained from 52 sources. The effect of variability and quantity of coke ash on blast-furnace operation is well known. The improved results obtained with furnaces operating on coke made from washed coals compared with results on coke made from raw coals is ample proof of the effectiveness of low and uniform ash. Coal-washing plants, however, require a large capital expenditure, and are impractical for most of the large number of small producers, whose operations are confined chiefly to periods of abnormally high demand. Furthermore, not all coals are physically adaptable to washing. PRINCIPLES OF IRON DESULPHURIZATION IN FURNACE Although investigations of the blast-furnace process have not clearly revealed the detailed mechanism of iron desulphurization within the furnace, they have been sufficiently extensive to permit a postulation of the following general principles: I. Iron, in its travel from furnace top to hearth, continues to pick up sulphur until it has reached tuyere level. The zone of iron desulphurization is relatively narrow, being confined to a vertical distance extending approximately from tuyere level to the iron-slag interface in the hearth.1 2. Combustion of coke is confined to spherical zones extending approximately 40 in. from the nose of each tuyere.2 Coke ash is released as the coke burns in these combustion areas. 3. With a constant amount of sulphur in the charge, the sulphur content of the metal product is a function of hearth temperature, final slag analysis, slag viscosity, and slag volume. Both hearth temperature and slag analysis affect slag viscosity. For a slag of constant analysis, viscosity always decreases with an increase in temperature;

Jan 1, 1943

By Carl G. Hogberg

During recent months, the acute shortage of steel scrap has necessitated the use of higher percentages of hot metal in the open-hearth charge. With these higher percentages, the sulphur content of hot metal has become an increasingly important factor in the control of the quality of steel. Thus, the blast-furnace operator is faced with a demand not only for more output but for a higher quality of product. More than go per cent of the sulphur charged into the blast furnace is contained in the coke. With the tremendously increased demand, the trend of coke quality has been toward higher sulphur, higher and more variable ash, and poorer physical characteristics. This has been brought about by less selective coal mining, increased production rates in coke plants and resumption of operations of many beehive ovens. In a single month last year, one blast-furnace plant in the Pittsburgh district operated with coke obtained from 52 sources. The effect of variability and quantity of coke ash on blast-furnace operation is well known. The improved results obtained with furnaces operating on coke made from washed coals compared with results on coke made from raw coals is ample proof of the effectiveness of low and uniform ash. Coal-washing plants, however, require a large capital expenditure, and are impractical for most of the large number of small producers, whose operations are confined chiefly to periods of abnormally high demand. Furthermore, not all coals are physically adaptable to washing. Principles 01 Iron Desulphurization in Furnace Although investigations of the blastfurnace process have not clearly revealed the detailed mechanism of iron desulphuri-zation within the furnace, they have been sufficiently extensive to permit a postula tion of the following general principles: 1. Iron, in its travel from furnace top to hearth, continues to pick up sulphur until it has reached tuyere level. The zone of iron desulphurizatioil is relatively narrow, being confined to a vertical distance extending zapproximately from tuyere level to the iron-slag interface in the hearth.' 2. Combustion of coke is confined to spherical zones extending approximately 40 in. from the nose of each tuyere.= Coke ash is released as the coke bums in these combustion areas. 3. With a constant amount of sulphur in the charge, the sulphur content of the metal product is a function of hearth temperature, final slag analysis, slag viscosity, and slag volume. Both hearth temperature and slag analysis affect slag viscosity. For a slag of constant analysis, viscosity always decreases with an increase in temperature;

Jan 1, 1943

By M. G. Nicholas

The influence of deformation, relative movement and surface cleanliness on the strength of room -temperature "interparticle" bonds between copper surfaces has been studied. No bonding resulted when clean surfaces were merely pressed together, even under pressures of 50,000 psi. Bonding resulted, however, when clean surfaces were simultaneously pressed and moved relative to each other, some bonding occurring no matter how small the pressure or relative movement. Exposure of the clean surfaces to various chemicals inhibited bonding, none at all being produced by small relative movements. The size of the movements which first produce bonding between exposed surfaces depends on the nature of the chemical, being less than 0.002 in. for cleansing reagents and greater than 0.004 in. for lubricants, water and hydrogen sulfide. It is concluded from the experimental data that the prime requirement for bonding is the dispersal of surface films such as oxides and adsorbed contaminants. THE formation of interparticle bonds during the room-temperature compaction of powder metallurgy components greatly increases the ease of handling in subsequent production operations prior to sintering. The strength of unsintered compacts follows the same general trends as their density and hardness, but quantitative data are extremely Scarce. Quantitative correlation of the data on the overall strength of a compact with that of the individual interparticle bonds is virtually impossible due to the extremely complex geometry of powder compacts. Qualitatively, however, the strengths of unsintered compacts can be correlated with variations in parameters known to influence the extent of cold bonding, and hence interparticle bonding, such as surface cleanliness, relative movement, and deformation of the mating surfaces. Kuzmic and seelig4 found that contamination of powder particle surfaces with lubricants reduced the strength of unsintered iron and copper compacts. Interparticle shear has been shown to promote bonding by Train and Hersey7 while Gregory has shown that die rotation is beneficial. Eilender and schwalbe6 concluded that most bonding occurred during the early stages of pressing iron powder compacts when interparticle shear is one of the principal processes occurring. mile there can be little doubt that these and other factors, such as particle size and shape, affect the extent of interparticle bonding produced by compaction, evaluation of the influence of individual factors is not easy. Particle deformation and relative movement, for example, occur simultaneously during compaction, making any precise measurement of their relative influences difficult. Because of these and other difficulties encountered in studying interparticle bonding in actual powder compacts, the approach adopted in this study was to

Jan 1, 1963

By Carl G. Hogberg

During recent months, the acute shortage of steel scrap has necessitated the use of higher percentages of hot metal in the open-hearth charge. With these higher percentages, the sulphur content of hot metal has become an increasingly important factor in the control of the quality of steel. Thus, the blast-furnace operator is faced with a demand not only for more output but for a higher quality of product. More than go per cent of the sulphur charged into the blast furnace is contained in the coke. With the tremendously increased demand, the trend of coke quality has been toward higher sulphur, higher and more variable ash, and poorer physical characteristics. This has been brought about by less selective coal mining, increased production rates in coke plants and resumption of operations of many beehive ovens. In a single month last year, one blast-furnace plant in the Pittsburgh district operated with coke obtained from 52 sources. The effect of variability and quantity of coke ash on blast-furnace operation is well known. The improved results obtained with furnaces operating on coke made from washed coals compared with results on coke made from raw coals is ample proof of the effectiveness of low and uniform ash. Coal-washing plants, however, require a large capital expenditure, and are impractical for most of the large number of small producers, whose operations are confined chiefly to periods of abnormally high demand. Furthermore, not all coals are physically adaptable to washing. Principles 01 Iron Desulphurization in Furnace Although investigations of the blastfurnace process have not clearly revealed the detailed mechanism of iron desulphuri-zation within the furnace, they have been sufficiently extensive to permit a postula tion of the following general principles: 1. Iron, in its travel from furnace top to hearth, continues to pick up sulphur until it has reached tuyere level. The zone of iron desulphurizatioil is relatively narrow, being confined to a vertical distance extending zapproximately from tuyere level to the iron-slag interface in the hearth.' 2. Combustion of coke is confined to spherical zones extending approximately 40 in. from the nose of each tuyere.= Coke ash is released as the coke bums in these combustion areas. 3. With a constant amount of sulphur in the charge, the sulphur content of the metal product is a function of hearth temperature, final slag analysis, slag viscosity, and slag volume. Both hearth temperature and slag analysis affect slag viscosity. For a slag of constant analysis, viscosity always decreases with an increase in temperature;

Jan 1, 1943

University of Washington, Engineering Experiment Station, Seattle, Wash For bulletins and reports address the Director. Of the many Bulletins and two Reports issued by the Engineering Experiment Station the following are of most direct interest in this directory:

Jan 1, 1933

References are in all cases to the earliest known editions. In the few cases where the first edition has been unavailable for consultation, the particular one studied is indicated. English translations are included when known, but not others. [ ]

Jan 1, 1942

F. W. Matthiessen, who, with E. C. Hegeler, of La Salle, was one of the creators of the zinc industry in the-United States, was born in Altona, Schleswig-Holstein, Germany, Mar. 5, 1835. He was one of a family of remarkable brothers, two of whom were long absociated in this country with the sugar and glucose industry. Mr. Matthiessen was educated at Freiberg, and came to this country in 1857 with Mr. E. C. Hegeler, after having, in company with that gentleman, visited the mining districts of Germany, Belgium, and England. They first went to Friedensville, near Bethlehem, Lehigh County, Penn., wherc attempts had already been made to produce zinc from the ore deposits found in that place. The ore was a he silicate but all attempts to extract zinc from it had failed. Mr. Matthiessen and Mr. Hegclcr were successful, but declined to invest their money in the zinc industry at Bethlehem because 01 certain local conditions. Hearing of the discovery of zinc -ore in the West, they visited both Wisconsin and Missouri and thought of settling in the coal region of East St. Louis. Finally La Salle, as being near to the Wisconsin fields and having much coal, was selected ae the site of the new smelting company, and on Dec. 24, 1858, the first shovelful of dirt was turned for the buildings of the new industry. The Civil War at first interfered with the manufacture of zinc, but afterward a lively demand for the metal arose and the future success of the institution was established. A large rolling mill was added in 1866, and in 1881 the manufacture of sulfuric acid as a byproduct was begun. Mr. Matthiessen also developed the Western Clock hlanufacturing Co. of La Salle, which manufactures the Big Ben alarm clock, from a small plant having 25 men to the present large institution which employs some 2000 workers. Mr. Matthiessen's affiliations with other metal industriefi have been numerous. But the contributions of the great zinc manufacturer to the causes of philanthropy and education have made his name known throughout the country, beyond industrial circles. He has given to the city of La Salle probably a sum total of $500,000 in various benefactions. Among the objects of his philanthropy were the La Salle-Peru Township High School, which he has made a model institution of secondary education for the entire United States; also the Tri-City Hygienic Institute of La Salle, Peru, and Oglesby, Ill., which he endowed for $200,000 This Hygienic Institute, which is unique in the United States, has a traincd staff of health officers, bacteriological laboratory, medical library, infant welfare station, milk station, free dental clinic, school nurse, and isolation hospital. Mr. Matthiessen was elected mayor of the City of La Salle three times and gave generously to the municipality of which he was the head. He also saved for the people of Illinois one of the great scenic districts of the state, Deer Park, with its cafions and natural beauties, which he con-verted into a model scenic resort, and the proceeds of which he gave to the charities of the Tri-Cities in which he lived. He died on Feb. 11, 1918.

Jan 1, 1920

By W. Rostoker, R. P. Elliott, B. W. Levinger

Phase equilibria in the Ti-Mn-Mo system have been investigated in the composition range 100 to 60 pct Ti and in the temperature range 550 to 1150°C. Three out of ten isothermal sections are presented as well as seven vertical sections, projections of the beta space and the surface of incipient melting. A STUDY of the system Ti-Mn-Mo was undertaken as part of a program to aid in the development of titanium-base phase equilibrium diagrams of potential technical importance to alloy development. The scope of the investigation included the composition range 100 to 60 wt pct Ti (all compositions refer to weight percentages) and the temperature range 550" to 1150°C. A surface of incipient melting was constructed from measurements of a large number of alloys. In the binary system Ti-Mo,' the high temperature modification of titanium generally spoken of as the p phase is stabilized to successively lower temperatures with increasing alloy content. There are no known intermediate phases, and complete miscibility exists between body-centered cubic titanium and molybdenum. The u solid solution is limited to less than 0.8 pct Mo at temperatures between 885" and 600°C. An equilibrium diagram for the binary system Ti-Mn has been published.' Manganese behaves as a p stabilizer but undergoes a eutectoid transformation at about 20 pct Mn and 550°C to a plus an intermediate phase. The structure of this phase has been found to be isomorphous with the a phase FeCr." Accordingly, the phase is assigned the formula TiMn, although its actual location on the composition scale has not been determined and may well be not exactly at the equiatomic composition. In disagreement with ref. 2, the origin of the TiMn phase has been shown' to be a peritectoid transformation at a temperature between 900" and 1000°C. A second intermediate phase occurs at the atomic proportions TiMn,. The structure of this phase was originally established by Wallbaum" as having a hexagonal lattice (C 14 type, 12 atoms per unit cell) isomorphous with MgZn,. In this work, the structure determination was confirmed and lattice parameters determined to be: a = 4.815 kX, c - 7.901 kX. Because of the extensive range of the P phase, the ternary system was suited to the determination of the phase boundaries by the parametric method of Andersen and Jette." During the course of the investigation, this method was found applicable only to the P/a+P boundaries but not to P/P+ compound boundaries. Metallographic methods were used alternatively for delineating these phase boundaries. Preparation and Treatment of Alloys Over 70 alloys were prepared for the study of this system. Ten gram alloy buttons were arc melted in a nonconsumable electrode furnace using inert atmosphere protection, and a water cooled copper crucible. The construction and operation of this type of melting unit has been described.' To insure complete solution of alloy additions, especially molybdenum, the buttons were remelted alternately on top or bottom as many as five times. This was accomplished by a suitable mechanism for "flipping" the ingots over. It was very difficult to obtain homogeneous melts in the region of less than 75 pct Ti because of the very high melting point of molybdenum and Ti-Mo master alloys and the comparatively low boiling point of manganese. Thus, the arc conditions for insuring complete solution of molybdenum were incompatible with the prevention of heavy losses of

Jan 1, 1955

By Carl S. Westerberg

Coal preparation practice and trends follow, among other factors, production trends in any given area. Considering an area the size of a state, some broad predictions may be made after a review of the annual production records. As this paper is concerned with coal cleaning in Utah, data on its production record are pertinent. Table 1 shows the percentage relation of coal production in Utah to the national total as a single figure up to 1935 which includes all recorded production. From 1935 through 1947 these data are presented by years. It is evident from these data that the production of Utah coal is ascending. The reason for this trend is industrial growth in the West resulting in a population shift which accounts for more people than the normal increase would supply together with Utah's relatively fortunate geographical location and its abundance of good-quality coal. Utah is also hopeful of supplying more coal in the future for West Coast power generation.I Utah is not unique among coal-producing states in anticipating greater production in the future. Coal Age states, " . . . it is now evident that a billion-ton yearly production of anthracite and bituminous by 1960 is not impossible." At present it is about 610,000,000 tons, the all-time high in 1947 was approximately 687,803,000 tons. In view of the trend outlined above, obviously more new mines will be required to produce the necessary tonnage. These in turn will require more mechanical cleaning capacity. Whether the required new plants will be built by present operators of mines and mechanical cleaning plants or by others now in the business of producing coal or expecting to enter it is of no consequence in this discussion. The fact is— they will be built.

Jan 1, 1950

By H. l. Burghoff

During the course of preparation of crystals of alpha brass for an investigation of their creep characteristics, a number of critically oriented crystals were produced. In each of these specimens, Po, the specimen axis, lay near some important crystallographic direction or on or near the border of two possible slip systems. Because of the unusual nature of their orientations, it was considered of interest to deform these specimcns in simple tension and to study orientation changes and any unusual occurrences, different from what would be expected for specimens ill which only one slip system had distinctly the highest maximum resolved shear stress. Choice of actual operating slip system in a crystal offering an immediate possibility of two slip systems would be expected to be due to chance., defeet, or some inhomogeneity. Even in an ideally perfect crystal so oriented, the natural oscillations of the atoms about their lattice positions would give rise to a condition wherein one slip system would be farored over the other at the critical shear stress. In the large, nonperfeet crystals of the present investigation, slip on both systems, but in different portions of the specimen, might occasionally be expected. Determination of Orientation and Operating Slip System Orientations of specimens before and after deformation were determined by Greninger&apos;s back-reflection Laue method.&apos; Elam2 has shown that deformation of alpha brass crystals proeceds as with crystals of aluminum and of copper; that is, the slip plane is a {111) plane and the slip direction is a <110> direction. There are, however, four possible slip planes of {111) form and each plane has three possible slip directions, so that there is a, total of 12 possible slip systems in a face-centered cubic lattjce. It is evident that the system for which the tangential component of shear is maximum will function

Jan 1, 1940

By H. l. Burghoff

During the course of preparation of crystals of alpha brass for an investigation of their creep characteristics, a number of critically oriented crystals were produced. In each of these specimens, Po, the specimen axis, lay near some important crystallographic direction or on or near the border of two possible slip systems. Because of the unusual nature of their orientations, it was considered of interest to deform these specimcns in simple tension and to study orientation changes and any unusual occurrences, different from what would be expected for specimens ill which only one slip system had distinctly the highest maximum resolved shear stress. Choice of actual operating slip system in a crystal offering an immediate possibility of two slip systems would be expected to be due to chance., defeet, or some inhomogeneity. Even in an ideally perfect crystal so oriented, the natural oscillations of the atoms about their lattice positions would give rise to a condition wherein one slip system would be farored over the other at the critical shear stress. In the large, nonperfeet crystals of the present investigation, slip on both systems, but in different portions of the specimen, might occasionally be expected. Determination of Orientation and Operating Slip System Orientations of specimens before and after deformation were determined by Greninger&apos;s back-reflection Laue method.&apos; Elam2 has shown that deformation of alpha brass crystals proeceds as with crystals of aluminum and of copper; that is, the slip plane is a {111) plane and the slip direction is a <110> direction. There are, however, four possible slip planes of {111) form and each plane has three possible slip directions, so that there is a, total of 12 possible slip systems in a face-centered cubic lattjce. It is evident that the system for which the tangential component of shear is maximum will function

Jan 1, 1940

By Martin E. Chenevert

The early work of Terzaghi1 showed that the true stress state of a rock can be expressed by the principle of effective stress. This principle states that effective stress is equal to total applied stress minus the pore pressure. Since the introduction of this principle, a great effort has been made to measure the pore pressure of rocks so that the true stress state can be determined. For clean, permeable sandstones, it is usually found that the effective stress principle can easily be applied. Direct measurement of the pore pressure is achieved with a hydraulic pressure device and the effective stress state thereby computed. However, for fine-grained rocks which contain large amounts of clay (referred to herein as shales), pore pressure measurements are usually quite difficult because of the adsorptive forces of the clay platelets, which produce negative internal pressures. No suitable device is known for measuring internal pressures of dry shales; the effective stress approach is therefore not feasible and data are usually presented in another form. As an example, data from compressive strength tests are presented as a function of rock wetness, rather than effective confining stress. The work of Belopoloskii2 and Colback and Wiid3 are examples of such data. It was pointed out by Lambe and Whitman4 that a better way must be found to express the effective stress of argillaceous rocks. The information presented herein is an attempt to fill that need. Various authors have been able to measure moderate negative pore pressures (0-240 psi) within rather wet, argillaceous rocks by means of various pore pressure devices. In 1961 Lambe5 resented information which shows that pore pressures in argillaceous rocks are indeed negative ; he presented values of suction pressure as low as - 14 psi. Likewise,

Jan 1, 1970

By J. R. Stone, J. T. Roy

ASARC09s continuous tapper for lead blast furnace is described. Its use throughout the company&apos;s plants has resulted in higher production rates, lower labor costs, and better working conditions. It has also permitted wide latitude in blast pressures, as well as in charge and slag compositions. The practice of tapping a lead blast furnace has remained essentially unchanged for many years. In principle, it is a batch operation discharging the products from the continuous smelting of lead-bearing materials. As such, it imposes certain restrictions on the proper functioning of the smelting operation. First, it calls for a highly developed sense of timing, and a considerable amount of physical effort on the part of the operator. Dirty and hot working conditions, as well as the hazards of flying metal and slag, usually prevail. These conditions have resulted in higher labor costs, both in rate and in amount. Labor turnover has also been high. Secondly, rigid control of mechanical and metallurgical factors must be maintained. Frequent oxygen lancing of the tap hole is needed to permit tapping, thereby increasing operating costs. Rapid increases in smelting rate, plugged tap holes, or forgetfulness on the part of the operator may permit the molten material to rise above the tuyeies and freeze the furnace. Also, the operator will often blow out the tap hole after draining, filling the area with fume. Composition of charge also vitally affects the tapping. The type of lead-bearing material being smelted will naturally affect the smelting rate, and thus the frequency of tapping. The amounts and types of fluxing materials, which determine the ultimate fluidity of the slag, must be regidly controlled. Finally, the batch tapping of a continuous smelting operation of this type appears to be wrong in principle. The molten material drains into the crucible at the bottom of the furnace where it starts cooling immediately and continues to cool until tapped out. While keeping the lead molten is no particular problem, maintaining a fluid slag at all times is often difficult, and sometimes impossible. These factors all point to the desirability of a method for the continuous tapping of a lead blast furnace. The expected advantages would be more desirable working conditions, lower labor costs, increased production, and a much wider latitude in both blast pressure and charge composition. CONTINUOUS TAPPING Historical. A number of devices, e.g., mechanical tappers, siphons, and lead wells, have been tried in the past in attempting to effect continuous tapping. None proved to be entirely satisfactory for tapping lead and slag simultaneously. It was not until 1955, however, that ASARCO designed and put into operation a successful tapping unit at its East Helena, Mont. lead smelter. This unit is described in detail in U.S. Patent NO. 2,890,951. Continuous Tapping Unit—See Figs. 1 and 2. Fig. 1 is a schematic drawing of the unit in place, showing front and side views. The component parts are identified in the caption. Fig. 2 is an actual photograph, front view, of the tapping unit attached to the base of the blast furnace. Operation. The operation of the tapping unit is quite simple. Essentially it consists of a narrow tapping bay surrounding the furnace tap hole, with a deep notch in the front wall. When the blast furnace is started this notch is open down to the level of the tap hole. Starting the furnace may be accomplished in several ways but the most satisfactory method is to plug the tap hole with clay, permitting metal and slag to build up inside the furnace. Before the liquid reaches the tuyeres, the plug is removed and the furnace is drained to the settler. The blast is then stopped momentarily while the notch in the front wall of the tapping bay is dammed with chrome brick and plastic chrome ore. The blast is again started, and the height of the dam is adjusted so that the liquid in the bay will counterbalance the internal pressure of the furnace. When the desired level is reached the slag and metal will overflow to the settler. It should be noted that the molten material ,is not siphoned from the furnace and that the metal &apos;acts as a liquid valve controlling the flow of slag through the tap hole. During normal operations the tapping bay is filled primarily with lead, covered with a thin layer of slag. Thus, the heavier lead plays the major role in compensating for variations in furnace pressures. Due to the high specific gravity of lead, changes in the liquid level in the tapping bay will never exceed a few inches. For this reason it is seldom necessary to change the height of the dam due to minor variations in operating conditions. Some turbulence of the liquid in the bay is essential at all times. This indicates that the level of the

Jan 1, 1963

By E. T. Turkdogan, W. L. Worrell

The rate of reaction of hydrogen sulfide with ferrous sulfide was studied by measuring the initial rates of sulfidation of iron strips in hydrogen sulfide-hydrogen-argon mixtures at 670°, 800°, and 900" C. The time-dependent surface sulfur activity is derived from the instantaneous rate of sulfidation with the assumption that diffusion in the sulfide layer is in a pseudo-steady state with the gas-sulfide chemical reaction. The rate of sulfur transfer from hydrogen sulfide to the surface of iron sulfide is proportional to the partial pressure of hydrogen sulfide and inversely proportional to the activity of sulfur at the surface of the sulfide layer. The derived rate equation is based on the assumption that most of the surface sites on the chemisorbed layer of iron sulfide are occupied by sulfur atoms and that the slow rate-controlling reaction is the dissociation of hydrogen sulfide on the chemisorbed layer. The experimental results are in reasonable accord with this reaction model. 1 HE slow approach to parabolic growth rate in the sulfidation of iron in hydrogen sulfide-hydrogen mixtures is a manifestation of slow approach to surface equilibrium between the gas and the surface of the sulfide layer. For example, at 800°C and Fig. 7 in Part I, the parabolic growth rate begins after approximately 1 day of sulfidation time. With decreasing temperature and decreasing partial pressure of hydrogen sulfide, the time necessary to reach gas-sulfide surface equilibrium is much longer. These observations are similar to those reported previously by Turkdogan et al.&apos; on the oxidation of iron to wustite in hydrogen-water vapor mixtures. The slow approach to gas-sulfide equilibrium is well-demonstrated by the results in Fig. 1 where the square of the weight gain per unit area, ( g S per sq cmI2, is plotted against time for gas mixtures having PH g//>H = 1.0 with 0, 25, 50, and 67 pct Ar at 800°C. The value of 1.5 X lo-&apos; (g S per sq cm)&apos; corresponds to almost complete sulfidation of the iron strip (- 0.05 cm thick) to iron sulfide. The points fall on S-shaped curves. If the inflection parts of the curves are considered to be linear, thus indicating parabolic growth rate and the establishment of gas-sulfide equilibrium, their slopes would have to be the same for a fixed ratio in the gas mixture. Such is not the case, and the slopes for the "linear" parts of the S-shaped curves are lower than the value when gas-sulfide surface equilibrium is established. The subject matter of this paper is the kinetics of the surface reaction of hydrogen sulfide with iron sulfide during the early stages of sulfidation of an iron strip. EXPERIMENTAL RESULTS The apparatus and materials used were the same as those discussed in Part I. In the present experiments of relatively short duration, a purified iron strip, 5 by 2 by 0.05 cm, which was suspended in the uniform hot zone of a vertical zircon tube, reacted with a flowing gas mixture of hydrogen sulfide-hydrogen-argon. The sample was suspended from a gold chain attached to a calibrated silica spring. The amount of sulfur picked up by the iron, which formed a layer of iron sulfide, was determined by measuring the displacement of a reference point on the silica spring, using a cathetom-eter. In all cases, the degreased sample was first annealed in a stream of oxygen-free dry hydrogen for several hours to remove any impurities such as oxygen, nitrogen, or carbon which might have been present on the surface of the sample.&apos; The rate measurements were carried out at 670°, 800°, and 900° C in hydrogen sulfide-hydrogen-argon mixtures with pH2 s/Ph2 ratios from 4 to 0.1. In a few experiments of short duration no sulfur deposition was observed in gas mixtures with (comments concerning sulfur deposition at high pH s/ph ratios were made in Part I.) Typical examples of the results obtained are shown in Fig. 2 for two temperatures and two gas compositions. With the present experimental technique, reproducible rate data could be obtained only after a uniform

Jan 1, 1969

By R. J. Wasilewski

Electrical resistivity variation with temperature was measured on a series of alloys containting up to 33 at. pct of oxygen over the range 77° to1500°K. The resistivity behavior is highly anomalous and itzconsistent with simple metallic conduction. Both composition and temperature-depended resistivity singularities were observed. A few experiments carried out on Ti-N and Zr-O alloys indicate the presence of similar anomalies. These observations, together with the published data on effects of substi-tutional alloying on the resistiuity of titanium, suggest that the anomalies are inhevent in the electron structure of this group oj metals. The existence of two-band conduction, and a significant shift of bands relative to each other with temperature and/or the electron concentration are suggested. CONSIDERABLE advances have been made in recent years in the alloy theory of simple metals. Very little, however, is known about the bonding in transition metals and their alloys.&apos; Titanium, with its relatively few electrons, may be expected to show simpler alloying behavior than the more complex transition elements. Its alloys with the interstitial elements appear particularly attractive in an investigation of bonding characteristics because of a) the simple nature of the solute elements, b) the remarkable similarity between the equiatomic structures Tic, TiN, and TiO, and c) the extensive solid solubility ranges of oxygen and nitrogen in a titanium reported.2,3 The Ti-O system was chosen for the most extensive investigation because of the relative ease of preparation of suitable specimens. Since the main object of the work was to obtain data on the bonding and its changes on alloying, electron-sensitive properties were primarily investigated. The present work describes the investigation on the electrical resistivity-temperature-oxygen content relationships. A few experiments were also carried out at selected compositions in the Ti-N and Zr-O systems. EXPERIMENTAL Materials and Method. Polycrystalline specimens were prepared in the form of hairpin strips some 50 by 5 by 0.15 to 0.50 mm by direct metal-gas reaction. This was carried out by controlled oxidation followed by a homogenizing anneal at a higher temperature. All the test specimens were fully homogenized as judged from the uniform microstructure and microhardness. To avoid preferred orientation, each strip specimen was annealed in the ß range prior to the oxidation, this procedure assuring random orientation in the strip;4 hence any texture resulting from the oxidation reaction itself affected all the specimens to a similar extent. Titanium used was of high purity (66 DPN, 10 Kg load; major impurities 0,-43G ppm, N,-70 ppm, C-25 ppm, Fe-14G ppm). The solute content of the alloys was determined by weighing, after the reaction with a known amount of oxygen. The specimens in which the discrepancy between the volumetric and gravimetric measurements exceeded 2 pct (or 0.2 mg for the low oxygen alloys) were rejected. The mean between the two measurements was then taken as the oxygen content of the alloy. Check analyses showed no measurable nitrogen contamination. All oxygen contents are given in atomic percent. Zr-O alloys were prepared in identical manner from hafnium-free crystal bar metal, cold-rolled to strip 0.25 mm thick. Ti-N alloys required very long reaction times at the maximum temperature available (1250°C). In order, therefore, to detect possible oxygen contamination, duplicate specimens were reacted in every experimental run, and one of these was analyzed both for oxygen (vacuum fusion) and for nitrogen (Kjeldahl). Only the specimens in which the check analysis showed < 1000 ppm O were then used for resistivity investigation. Since only relatively high nitrogen alloys (7.1 at. pct; i.e., 2 wt pct N,) were investigated, this oxygen contamination was considered permissible. Dc resistance was measured by the four-probe method as previously described.= The temperature was determined with a calibrated thermocouple placed in the center of the specimen hairpin. The errors in the specimen resistance values thus obtained were estimated at 1 pct due almost exclusively to the finite thickness of the potential wires and the consequent uncertainty as regards the true resistance length of the specimen. For the calculation of the specific resistance, however, no dimensional measurements could be carried out on most of the

Jan 1, 1962