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Executive ERLE V. DAVELER. Chair u W. B. HEROY PAUL D. MERICA JOHN M. LOVEJOY WILLIAM WRAITH Finance H. G. MOULTON, Chairman H. T. HAMILTON HENRY KRUMB Admissions JOHN L. CHRISTIE, Chairman GEORGE D. BARRON, Vice-Chairman FRED H. KAY PHILIP KRAFT H. Y. WALKER

Jan 1, 1938

The Library of the above-named Societies is open from 9 A. M. to 10 P. M. except on holidays. It contains about 70,000 volumes and 90,000 pamphlets, including sets of technical periodicals and publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library, through its Library Service Bureau, can render valuable service through correspondence; letters requesting information will receive especial attention. The Library is prepared to furnish references, and photographic copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information on the geology and mineral resources of all countries. All communications should be made as definite as possible so that the information received may be what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will be saved, and the information will be sent more promptly and in more usable shape.

Jan 4, 1918

By W. D. Robertson, E. Scala

Electrical resistivity of a number of pure liquid metals and alloys has been measured as a function of temperature and composition. The data show a close correspondence between the liquid and solid states with respect to thermal, structural, and compositional relationships. STUDY of diffuse scattering of X-rays by liquid metals1 has demonstrated that some degree of order persists above the melting point and that the atomic constitution of liquids is more analogous to the solid state than to a gas. Consideration of the change in various thermodynamic properties that accompanies transformation from solid to liquid leads to the same general conclusion.² evertheless, specific knowledge of the constitution of the liquid state is limited when compared with that of the solid and gaseous states owing, in part, to the difficulty of interpreting the X-ray data and in part to the indirect character of deductions based on thermodynamic data. Of the structure-sensitive physical properties, electrical resistivity of liquid metals is perhaps the most easily interpretable, particularly when comparison is made with the solid state. According to the available data, most of which was obtained prior to 1914, cubic metals exhibit a normal linear and positive temperature dependence in the liquid state and the data have been accepted without question. The divalent metals, zinc and cadmium, are apparently exceptional in that resistivity is not linear with temperature and it passes through a minimum. Mercury also exhibits a nonlinear temperature dependence but the slope is always positive. Important comparisons with magnesium could not be made at the time the following work was undertaken because the necessary experimental data were not available. Data on liquid solutions are very limited and are largely from a single source."-" Based on Bornemann's work, Norbury7 pointed out that the resistivity of liquid copper alloys appeared to be dependent on the valence of the solute and that the increase due to the solute was of the same order as in the solid state. However, large extrapolations were involved and no quantitative relationship was developed. Therefore, before proceeding with additional deductions regarding the resistivity of liquid metals and interpretation in terms of structure, it appeared necessary to verify and extend the previous work with particular emphasis on divalent metals and the effect of alloying elements of different valence in dilute liquid solutions. The present work includes: 1—A determination of the resistivity of high purity liquid magnesium, tin, indium, copper, zinc, and cadmium as a function of temperature. 2—The effect of 1 atom pct of copper, cadmium, aluminum, tin, antimony, and

Jan 1, 1954

By L. W. Page

PREVIOUS to the introduction of the motor vehicle the broken stone or macadam road met the conditions of rural horse-drawn traffic better than any other type of road, but under fast motor traffic it has been proved to be quite unsatisfactory, and necessitates high maintenance charges. Such a road depends for its success upon the fact that the rock dust fills the voids between the stones and acts as a cement or binder. Under ideal conditions it should be constructed of rock so suited to the volume and character of horse traffic that only enough fine dust is worn from the stones of which the road is composed to take the place of that carried off by wind and rain; and when these conditions are met, the fine dust resulting from the wear. of traffic forms with the stone a smooth, impervious shell, shedding the surface water and protecting the foundation. With increase in the number and speed of motor vehicles, however, it was soon found that the cost of maintenance also increased, until at the present day highway engineers consider the old method of constructing and maintaining broken-stone roads increasingly inadequate, and are introducing every known type of binding material other than rock dust to cement the stone together. Among the most prominent types of products in use are those produced from our various petroleums. That the value of modern methods of road preservation was appre¬ciated in this country much earlier than we have been accustomed to believe is demonstrated by the recent revival of an old patent which was granted to one John Martineau, of Elbridge, N. Y., in 1834. Petroleum had, of course, not been discovered at that time, but he claims as his invention and improvement "The application of tar, turpentine, or any of that class of tenacious, cohesive substances, reduced before use to a fluid state, and that state used as a cement, to apply to, and combine with sand, gravel, pebbles, and pulverized stone, such as is used for a Mc-Adam road, or cobble stone, the interstices of coarser material being in all cases filled, as well as may be, with sand and gravel and cemented with tar or turpentine, to form the wearing face or surface of streets,

Jan 2, 1914

By M. R. Tek

General equations relating the pressure drop necessary to sustain the flow of a fluid through a porous matrix at a given rate have been developed. The results indicate that at high values of flow rate the pressure-flow behavior may not necessarily satisfy the usual Darcy equation. The mathematical analysis, carried through the micro-pore geometry and extended through the macro-reservoir scale, indicate that Darcy's law, of limited applicability to certain ranges of Reynolds numbers, can be generalized through the inclusion of some additional parameters. The "generalized Darcy equation" has also been formulated in dimen-sionless form permitting the evaluation of its predictive accuracy with regard to literature data. A comparison between predicted and experimental values indicates that the generalized Darcy equation predicts the pressure drops with good agreement over all possible ranges of Reynolds numbers. INTRODUCTION The limits and the nature of validity of Darcy's law' has been a subject of every-day interest to the industry for many years. It is well known that as the Reynolds number, characteristic of the fluid flow through porous media, becomes large, Darcy's law gradually loses its predictive accuracy and ultimately becomes completely void. For the last 20 years much has been said and written on this subject. Unfortunately little has been accomplished to bring about a satisfactory agreement, at least on the nature of the threshold of validity of Darcy.'s law. Fluid dynamists, geo-physicists, and engineers all had their individual views, explanations, interpretations and concepts on the subject. To some, a mechanistic analogy with pipe-flow proved a satisfactory explanation.' To others,' turbulence, in its random character, was incompatible with the geometric structure of consolidated porous systems. To some,4 turbulence merely represented a factor influencing the permeability measurements and again to others5,6,7 em-pirical or semi-empirical correlations proved satisfactory from an engineering viewpoint. Deviations from Darcy's law at high flow rates have been studied by systematic experiments by Fancher, Lewis, and Barnes.' In an article on the flow of gases through porous metals, Green and Duwezs conclude that the onset of turbulence within the pores appears unsatisfactory to explain deviations from Darcy's law. This view is held by many others. While the subject remained controversial for many years, the development of vast natural gas reserves throughout recent years further justified considerable interest on this problem from the standpoint of gas reservoir behavior. As large amounts of field data became available from the operation of many gas fields, it became evident that the steady-state behavior of gas wells was not, in general, in agreement or compatible with Darcy's law. This suggested a careful reconsideration of all mechanisms which may account for pressure drops in addition to viscous shear. In a series of articles9,10 . Hou-peurt indicated that deviations from Darcy's law may be explained on the basis of kinetic energy variations and jetting effects without resorting to assumptions on turbulent flow conditions. Another article by Schneebeli11 indicates that special experiments by Lindquist clearly demonstrated that the onset of turbulence does not necessarily coincide with conditions of deviation from Darcy's law. This view is also held by M. King Hubbert.12 Starting with the basic pressure-flow relations suggested by Houpeurt, the derivation, development and extension of analytical expressions to -supplement and generalize Darcy's law has been the objective of this work. MATHEMATICAL ANALYSIS Derivation of Dimensionless Pressure-drop, Flow-rate Relations In considering the flow of a fluid through a porous matrix geometrically represented by a succession of capillary passages in the shape of truncated cones,810 an approximate expression may be derived relating viscous and inertial, i.e., total pressure drop to the physical properties of the fluid, geometric properties of the rock matrix and the rate of flow: ?P/?r = µ/k V [ 1 + c(m4 - 1) p V/16n" mµ w] ..........(1) Let us formally set: c (m4 - 1) / 16n" m = a d ......(2) Such a representation is equivalent to assert that the term [c(m4 — 1)/ 16n"m], variable with various porous media and probably highly variable within a given porous medium, may be macroscopically defined as equal to a lithology factor times the aver-age grain diameter d. In view of the usual grain and pore size distribu-

Jan 1, 1958

(Members are urged to send in for this column any notes of interest concerning themselves or their fellow-members.) Members and guests who called at Institute headquarters during the period May 10, 1916 to June 10, 1916: G. Aertsen, Philadelphia, Pa. Hennen Jennings, Washington, D. C. Frederick C. Alsdorf, Wickenburg, Ariz. H. M. LaFollette, LaFollette, Tenn. A. H. Anderson, Worcester, Mass. E. T. Lednum, Chicago, Ill. J. H. Batcheller, Mattapoisett, Mass. Francis Church Lincoln, Reno, Nev. Arthur B. Clark, Sheridan, Mont. H. Mortimer-Lamb, Montreal, Canada. J. Murray Clark, Toronto, Canada. Andrew W. Newberry, San Francisco, Cal. J. H. Collier, Oakland, Cal. C. E. Pettibone, Cleveland, 0. H. S. Emlaw, Spring Lake, Mich. Heinrich Ries, Ithaca, N. Y. E. L. Estabrook, Platteville, Wis. C. S. Robinson, Youngstown, 0. James W. Hambleton, El Paso, Tex. - M. K. Rodgers, Basin, Mont. James Henderson, London, England. E. J. Rossbach, St. Louis, Mo. G. P. Hulst, East Chicago, Ind. J. B. Tyrrell, Toronto, Canada. William F. Jahn, Riebeling, Mont. G. B. Waterhouse, Buffalo, N. Y.

Jan 7, 1916

By Lysle E. Shaffer

INCREASING attention has been given in the last decade to the possibilities of mine leasing in the West. The practice as described in this article does not refer to the leasing of entire properties for corporate operation. It is intended to deal rather with the advantages and problems incident to leasing portions of properties to individuals who themselves, individually or in groups, do the actual mining and transportation of the ore. These individuals are sometimes called "leasers" and sometimes called "tributors." The contracts under which they work set up an independent relationship of lessor and leaser, between themselves and the mineowner or operator. This relationship has many advantages to both sides over those created by the ordinary relationship of employer and employe. From the standpoint of the owners there is no liability on independent contractors for industrial injuries, social security taxes, unemployment taxes, or the manifold restrictions of the Federal Labor Relations and Wage Hour Acts and similar state acts where they exist. As the leaser's income depends on the quantity and quality of ore produced, there is a distinct incentive for maximum production of a good grade of ore. This in turn promotes careful mining of the areas under lease. Ordinarily in mining, labor cost is a high percentage of the total cost of operation. Under a leasing system, even if the leasers be allowed to retain half of the gross values that they produce, and the owner or operator gets half, in the case of marginal ore bodies this is ordinarily more than the lessor would realize if the property were worked by day labor. In some instances mineral deposits under a leasing system may become ore, whereas under a day-labor system they would

Jan 1, 1948

By K. R. Evans

The yield and fracture characteristics of a Ti-8 pct A1 alloy have been examined at room temperature as a function of exposure temperatures to 1700°F. Em-brittlenzent of the alloy is observed to occur following exposures below 1280°F, the critical temperature for formation of ordered Ti3Al particles. Presence of Ti3Al particles results in an increase in the yield and flout stresses which, for a given exposure time, are a maximum at the critical temperature. Embrittlement is attributed to the occurrence of plastically induced fracture controlled by the increase inflow stress. This interpretation is compatible with the decreasing ductility and increasing crack popagation rates observed with increasing exposure time below the critical temperature. Slip line observations and measurements of the gain size dependence of the yield stress indicate that the slip character of the alloy is not influenced by exposure treatments below the critical temperature. ThE potential usefulness of Ti-A1 alloys in structural applications has prompted considerable interest in studies of their microstructure and mechanical characteristics. The relatively recent surge of interest in the system and at the same time its complexities are indicated by the fact that despite numerous recent efforts14 there has not even been general agreement upon a phase diagram for the system. However, most of the Ti-A1 alloys of commercial interest range in aluminum content from 5.0 to 8.5 wt pct where most investigators achowledge the existence of the ordered Ti41 phase. Goldak and parrs confirmed the existence of Ti41 from X-ray diffraction analysis of the stoichiometric composition while Blackburn6 has determined its presence in commercial Ti-8 pct A1 alloys by electron diffraction analysis and dark field transmission microscopy. The embrittlement of Ti-8 pct A1 alloys was initially reported by Crossley and carew7 who showed that aging in the temperature range of 750" to 1110°F resulted in extreme brittleness. This behavior was later confirmed and correlated by Soltiss to the presence of long-range order in the commercial Ti-8 pct Al-1 pct Mo-1 pct V alloy (Ti-8-1-1) which exhibited anomalous creep and yield strength behavior at 950°F. This investigation was designed to study the mechanical characteristics of a binary Ti-8 pct A1 alloy in order to further examine the nature of the embrittlement behavior reported for the alloy system. EXPERIMENTAL PROCEDURE A Ti-8 pct A1 binary alloy was obtained from the Wah Chang Co. in the form of 0.050 in. sheet. The chemical composition of the alloy is given in Table I. Heat-treatment of the alloy was conducted in evacuated vycor capsules for the tensile sDecimens (1.25 bv 0.25 in. gage section) and in evacuated stainless steel jackets for the crack growth-rate panels. All specimens were annealed at 1700°F for 24 hr and water quenched before an exposure at elevated temperatures. Tensile testing was conducted at room temperature in an Instron testing machine equipped with a pushbutton control for instantaneous control of the cross-head motion. In this manner the change in stress, Aa, accompanying an increase in strain-rate by a factor of 10 was measured immediately after yielding. The crack growth-rate panels used were 3 by 18 in. with a precrack 0.33 in. long cut into the center of the panel. The panels were cycled at a maximum gross stress of 40,000 psi at a maximum to minimum tension stress ratio of 20. Cycling of the specimens was continued until the crack propagated the width of the panels. The crack length was intermittently measured during slow crack growth. EXPERIMENTAL RESULTS Correlation of Embrittlement to the Critical Temperature for Ordering. Blackburn6 has found that the critical temperature, T,, for the formation of Ti41 in a Ti-8 pct A1 alloy with an interstitial content on the order of that given in Table I is approximately 1245°F. The relationship between the ductility of the binary alloy used in this investigation and T, was estimated from tensile tests on specimens which were exposed for 24 hr at various temperatures followed

Jan 1, 1970

By Charles C. Peterson, Ronald E. Enstrom

Significant improvements have been made in the ursine systern for epitaxial vapor gvowtlz of Gds. The electron concentration has been reduced to below 1015 cm-3 with electron-mobility values as high as 7200 sq on per v-sec at 30PK and 60,000 sq cw7 per v-sec at 77°K. These high-purity layers have been successfully gvown on n&apos; layers with thicknesses as snzall as 1 p and as large as 125 p. Furthermore, high-purity layers have been incorporated into an structure without degradation of electrical properties. Different impurity gradients at the n&apos; to n interface were achieved. Using these structures, Gunn oscillators have been operated at frequencies as low as 0.4 GHz and as high as 40 GHz, which equals the highest valzle yet reported. The frequencies nleasured are in reasonable apeenlent with those calculated fron7 the n-layer widths and the transit times. CW operatiolz has been achieved from 3 to 20 GHz. In Gunn devices for >40 GHz operation (i.e., witk an n-layer tkickness below 2.5p), the n layer has been generally too pure to permit oscillations to occuv. ThE mechanism of the Gunn oscillator&apos; is now generally understood.2-5 Electron transfer from the (000) minimum to the ( 100) minima leads to a voltage-controlled negative resistance, which results in the formation of domains of high and low electric fields which travel through the crystal with a characteristic velocity of about 107 cm per sec. When a constant voltage is applied to the sample, this domain motion generaliy leads to oscillations at the transit time frequency, fT = 107/L, where L is the thickness of the active n layer.&apos; In this case, a single high-field domain is nucleated at the cathode and grows until it reaches the anode, where it is absorbed; a new domain then forms at the cathode.5 There are related modes of oscillation of the same device in which a tuned circuit causes a periodic variation of the voltage across the device. The frequency then may be either above or below fT. It has been shown that oscillations will occur when n • L 2 1012 cm"2, where n is the carrier concentration in the active region. At lower doping densities, 10" 5 n . L 5 lo&apos;&apos;, the doping is said to be subcritical for oscillation and the description of the device operation changes since the domains become comparable in thickness to the device thickness, L. Nevertheless, such devices have been found to be "active" and, in fact, are useful as amplifiers.778 For CW operation, one wishes to minimize the power dissipation, which is related to the electric field, E, and the low-field resistivity, p. Below threshold, the power dissipation density is approximately Typically, at threshold where E -- 3 x 103 v per cm, the dissipation density is 107/p watts per cu cm, p in ohm-cm. Furthermore, it is desirable to provide good conduction of the heat generated in the active region. The temperature rise, AT, across the active layer of a sandwich structure, with a heat sink on one side, is given by AT = (E&apos;/P)(L~/~~) where it is assumed that the thermal conductivity, u, and resistivity, p, of GaAs do not vary appreciably over the range of temperature and electric fields existing in the layer. This expression shows that, subject to maintaining an appropriate (n . L) product, CW operation is favored by a higher resistivity, a lower threshold field, and a thinner device. The above device requirements place some severe restrictions on the materials to be used, especially for high-frequency (>10 GHz) operation. Here, it is necessary to prepare very thin (<10 µ) layers of GaAs, in a state of high purity (-1 ohm-cm), complete with very low-resistance ohmic contacts. Problems of handling such thin and fragile samples become inereasingly severe as the frequency is raised. Furthermore, while good low-resistance ohmic contacts are easily applied to low-resistivity GaAs, contacting difficulties are encountered for these higher-resistivity materials.

Jan 1, 1968

Jan 1, 1885

By Y. Kondo, S. Yamazaki, Z. Asaki

Thermal deco7nposition of Pyrite particles in a fluidized bed with inert gas stream was studied. Assuming that heat transfer from the surroundings to the fluidized particles controls the overall decomposition rate, rate equations for the batch process and for the continuous process were derived. In the batch experiment, a linear rate equation satisfies the experimental results and the overall heat transfer coefficient calculated from the rate constant agrees fairly well with that obtained by Leva.l1 For the continuous process, two rate equations were derived, one on the assumption of complete mixing of particles and another on the upward piston flow of particles in a fluidized bed. The former holds for a bed containing a higher fraction of decomposed pyrite realized at lower feeding rates. The latter can be applied for a bed at higher feeding rates. Thus, segregation of particles in the fluidized bed was indicated at higher feeding rates. Bed temperatures also correspond to these conditions. ThERMAL decomposition of pyrite may be represented by Eq. [I]. The pressure of diatomic sulfur gas reaches 1 atm at about 690°C. The thermodynamics,&apos; kinetics,2&apos;3 composition, and properties3-5 of decomposed products of such a reaction have been studied. Pyrite is a very common sul-fide mineral and is often accompanied with other sul-fides. It is of basic interest in nonferrous metallurgy to clarify the behavior of pyrite in the pyrometallur-gical processes of sulfide minerals of metals such as copper, lead, zinc, nickel, and so forth. Interest in this reaction increased recently because of possible elimination of arsenic from pyrite in processing highly purified iron oxide pellets. Producing elemental sulfur from pyrite, instead of sulfuric acid, also aroused interest in this reaction. It is indicated that the thermal decomposition of solid particles, such as calcium carbonate, proceeds through three major sequential steps: heat transfer, interfacial chemical reaction, and mass transfer.637 It is known that the decomposed product of pyrite is very porous2, 3 and the diatomic sulfur gas evolved can easily escape through this layer of decomposed product. It depends upon the circumstances, therefore, whether the heat transfer to the interface within particles or the chemical reaction at the interface determines the overall decomposition rate. The enthalpy change in the decomposition of pyrite is about 33 kcal per mole FeS2 which is comparable to that of calcium carbonate. The decomposition of calcium car- bonate becomes more and more dependent on the rate of transport of heat when reaction temperature increases, such as occurs in a fluidized bed.6&apos;7 It is reasonable to presume, therefore, that the thermal decomposition of pyrite, an endothermic process, carried out in a fluidized bed may be analyzed according to the heat transfer controlling model. This work intends, first, to propose a mathematical model that determines the overall rate in a fluidized bed for the decomposition process and, second, to investigate a few characteristics of the fluidized bed based upon the experimental results obtained. KINETICS OF THERMAL DECOMPOSITION IN A FLUIDIZED BED It is intended in this section to obtain rate equations for thermal decomposition of pyrite in a fluidized bed by assuming that the overall rate is determined by heat transfer from the surroundings to the particles. Both batch and continuous processes are considered. 1) Batch Process. To obtain the rate equation in the batch process, the following two additional assumptions are made. First, the temperature of preheated inert gas, tg, blown into the fluidized bed is assumed to be the same as the temperature of the fluidized bed, tf. Thus, no heat exchange occurs between the gas and particles in the bed and only the heat transfer from the reactor wall kept at tw to the particles is to be considered. Second, the decomposition is assumed to start at the outer surface of the particles and to proceed toward the center. At any given time during decomposition, undecomposed pyrite remains in the tori at a temperature: td. The decomposed shell is composed of FeS1+x whose outer surface is at tp Diatomic sulfur gas evolving at the interface is heated to tf during its escape through the decomposed shell. This is illustrated in Fig. 1. With the above-mentioned assumptions of heat transfer, we have:

Jan 1, 1969

The library of the above-named Societies is open from 9 A.M. to 10 P. M. except on holidays. It contains about 70,000 volumes and 90,000 pamphlets, including sets of technical periodicals and publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library, through its Library Service Bureau, can render valuable service through correspondence; letters requesting information will receive especial attention. The Library is prepared to furnish references and photographic copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information on the geology and mineral resources of all countries. All communications should be made as definite as possible so that the information received may be what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will be saved, and the information will be sent more promptly and in. more usable shape.

Jan 8, 1918

The library of the above-named Societies is open from 9 A. M. to 10 P. M. except on holidays. It contains about 70,000 volumes and 90,000 pamphlets, including sets of technical periodicals and publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library, through its Library Service Bureau, can render valuable service through correspondence; letters requesting information will receive especial attention. The Library is prepared to furnish references and photographic copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information on the geology and mineral resources of all countries. All communications should be made as definite as possible so that the information received may be what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will be saved, and the information will be sent more promptly and in more usable shape.

Jan 1, 1919

By R. E. Miner, J. K. Jackson, T. L. Wilson

A study has been made of the transformation kintetics and morphology in gas-quenched Fe-5 pct Ni alloys. Massive ferrite or nlurtensite was found to form at temperatures in agreement with earlier results. Surface Preparation appeared to have the greatest effect in determining the type of transformation Product formed. Grain size change, subgrain morphology, and dislocation densities of massive ferrite were essen-tinlly invariant functions of cooling rate. The mar-tens~tic structures were typical of transformation in austenite grains of the order of the sample thickness. BY introducing the idea of a massive transformation in dilute iron-base alloys, Gilbert and Owen in 1962 served to stimulate a closer inspection of phase transformations in ferrous systems.&apos; A wealth of literature has followed concerned with the morphology,2-5 transformation mode,2&apos;3&apos;6-8 and thermodynamics of transformations.2,5,9 interesting controversies have resulted from the experimental observations; closer attention has been paid to the definition of massive transformations and still to be resolved is the Ms temperature of pure iron. The purpose of this note is to report some observations made in a detailed kinetic and metallographic examination of the transformations that occur in gas quenched Fe-5 pct Ni. The results are pertinent to the Ms extrapolations that have been made for pure iron and the observed substructure of massively transformed alloys. PROCEDURE The material used in this investigation was cast as a 5 lb vacuum induction melted, carbon deoxidized heat. The ingot was hot worked to a strip 0.10 in. thick, decarburized, and cold rolled to final thickness. Specimens were punched to sample shape and decarburized in wet hydrogen at 600°C. The chemistry of test specimens is indicated in Table I. Samples 1 by $ in., by thickness were resistance heated and rapidly cooled in an apparatus as illustrated in Fig. 1. Similar helium quenching apparatuses have been described previously;2,6&apos;10 the distinguishing feature of this apparatus is the nozzle geometry. Twin nozzles with three convergent-divergent, sonic ports were mounted perpendicular to the specimen for quenching purposes. The specimen temperature was monitored with an intrinsic 3 mil chromel-alumel thermocouple spot welded to the specimen and con- nected to an oscilloscope. A single switch stopped the current flow through the specimen, opened a gas flow solenoid valve, and initiated an oscilloscope sweep. Cooling rates were read directly from a photograph of the oscilloscope trace and the quenching rates quoted later were made at a point immediately prior to transformation on the trace. All quenching studies were conducted either under a vacuum of 10"-5 torr or a helium atmosphere. The sample geometry was chosen large enough to permit optical and electron microscopy to be performed on samples. The samples were electropolished for both types of examination in a perchloric-acetic solution. Electron microscopy was conducted on a HU 11A microscope operated at 100 kv. Dislocation densities were determined at the same general operating reflection (110) on foils thick enough to produce Kikuchi patterns. RESULTS AND DISCUSSION Transformation Temperature Observations and OD-tical Microscopy. The quenching results of this study are illustrated in Fig. -2(a). Samples which were treated in the as-decarburized condition transformed in a manner similar to that reported previously—a decrease in transformation temperature occurred as the quenching rate increased until a plateau region was reached. Within the scatter of the results obtained here, there was no break in the transformation temperature-quenching rate plot. This suggests no change in transformation mode. Further metallographic examination confirmed this observation. A martensitic transformation was obtained for similarly treated samples except that the surface was first electropolished. The Ms temperature was approximately 85°C below the plateau determined for the unpolished samples and cooling rates as slow as 2000°C per sec were adequate for producing marten-site. The transformation temperatures are in gen- / STRIP SAMPLE / COPPER I SAX/-/}&apos; / CONNECTOR-----A f, SON|C poRTS AC LEADS 3j ]j"I rofe[ \ Mf/yinK/iKj&apos;&apos;^ THERMOCOUPLE X-(^—iie"s*c? &apos; LEADS 1 INCH Fig. 1-—Schematic scction of gas quenching apparatus

Jan 1, 1970

The Library of the above-named Societies is open from 9 A.M. to 10 P.M., except on holidays. It contains about 70,000 volumes and 90,000 pamphlets, including sets of technical periodicals and the publications of - scientific and technical societies members of the Institute, with few exceptions, are forced to spend a portion of their time &apos;in localities isolated from sources of information. To these the Library, through its Library Service Bureau, can render - valuable service through correspondence; letters requesting information will receive especial attention. The Library is prepared to furnish references and photographic copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish genera1 information on the geology and mineral resources of all countries. All communications should be made as definite as possible so that the information received may be what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will be saved, and the information will be sent more promptly and in more usable shape.

Jan 10, 1916

The library of the above-named Societies is open from 9 A. M. to 10 P. M. except on holidays. It contains about 70,000 volumes and 90,000 pamphlets, including sets of technical periodicals and publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library, through its Library Service Bureau, can render valuable service through, correspondence; letters requesting information will receive especial attention. The Library is prepared to furnish references and photographic copies of articles on mining and metallurgical subjects; to determine the existence of mining, maps, and to furnish general information on the geology and mineral resources of all countries. All communications should be made as definite as possible so that the information received may be what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will be saved, and the information will be sent more promptly and in more usable shape.

Jan 2, 1919

The library of the above-named Societies is open from 9 A. M. to 10 P. M. except on holidays. It contains about 70,000 volumes and 90,000 pamphlets, including sets of technical periodicals and publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library, through its Library Service Bureau, can render valuable service through correspondence; letters requesting information will receive especial attention. The Library is prepared to furnish references and photographic copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information on the geology and mineral resources of all countries. All communications should he made as definite as possible so that the information received may be what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will be saved, and the information will be sent more promptly and in more usable shape.

Jan 11, 1918

The library of the above-named Societies is open from 9 A.M. to 10 P. M. except on holidays. It contains about 70,000 volumes and 90,000 pamphlets, including sets of technical periodicals and publications of scientific and technical societies. Members of the Institute, with few exceptions, are forced to spend a portion of their time in localities isolated from sources of information. To these the Library, through its Library Service Bureau, can render valuable service through correspondence; letters requesting information will receive especial attention. The Library is prepared to furnish references and photographic copies of articles on mining and metallurgical subjects; to determine the existence of mining maps, and to furnish general information on the geology and mineral resources of all countries. All communications should be made as definite as possible so that the information received may be what is desired and not include collateral matter which may not be of interest. The time spent in searching for such collateral matter will be saved, and the information will be sent more promptly and in more usable shape.

Jan 10, 1918

By A. G. Guy

Thermodynamic activity rather than chemical composition is basic to the analysis of diffusion. This is the essential conclusion reached by Darken1-3 and by Birchenall and Mehl.4 If so, it is reasonable to expect that diffusion calculations should be carried out using activities. This paper will illustrate a method of employing activities in analyzing interstitial diffusion. For interstitial diffusion (of carbon in iron and probably generally) the diffusion of the solvent atoms, volume changes, and other such complexities not explicitly provided for in the usual diffusion equations cause a negligible error of the order of 1 pct. Therefore it is relatively easy to test the validity of an analysis based on activities in the instance of interstitial diffusion. The mathematical treatment of the more complex substitutional diffusion could be simplified once the adequacy of the activity method had been established for substitutional diffusion. Thus the present work has the purpose not only of providing a superior analysis of interstitial diffusion but also of indicating a possible approach to the more important question of an adequate treatment of substitutional diffusion. Development of the Diffusion Equation Although activities are convenient quantities to determine experimentally, they are derived from the more fundamental fugacities.9 Possible confusion in using activities can be avoided by basing equations involving their use on the relationship, dP = -D1d/ax dt [I] where, dP = the number of grams of solute crossing one cm2 in the time dt sec. D, = the diffusion constant for use with fugacities; it is assumed to be constant at a given temperature, and has units of secs. f = the fugacity of the solute in the solid solution; the units are those of pressure, dynes per cm2. x = the distance in cm. Eq 1 can be considered to be the basic form of the first Fick Law for one-dimensional diffusion. In order to convert Eq 1 into an equation involving activities, a choice of a standard or reference fugacity, f°, must be made: then. a = f [2] where a is the activity corresponding to the fugacity f. However, the value of a is also determined by the relation, a = a\c [3] where a is the activity coefficient and c is the concentration. For a given value of a (such as a = 1) it is evident that the units used for expressing concentration will affect the numerical value of a corresponding to a given amount of carbon dissolved in y-iron. Since weight per cent concentration is so widely used, this unit will be adopted as the standard in this paper. When the value off given by Eq 2 is substituted in Eq 1, the first Fick Law becomes, dP= -D,f°dl [4] Since D,f° is constant (at a given temperature), the second form of Fick&apos;s Law can be obtained in the usual manner, -dt D&apos;f° dx [5] where c&apos; is the concentration in g per cm3. In terms of weight per cent concentration, c, Eq 5 becomes, dc _ 100 d2a Tt = T /f w [6] where p is the density of the solid solution and will be assumed to be constant. In order to simplify Eq6, it is necessary to consider the standard state, f°. Standard states are chosen for convenience. There appears to be one especially convenient choice for the analysis of interstitial diffusion. If the activity coefficient, a, is set equal to unity at infinite dilution of the solute, 100 then — 100D1fl° is approximately equal P to the usual diffusion constant in dilute solutions. This is true since the activity, a, in Eq 6 can be replaced by the concentration, c, with little error in an infinitely dilute solution.* Here f1° is the standard fugacity necessary to achieve this standard state. It is proposed that a diffusion constant Da&apos; be defined, Da1=100/pD1f1° [7] where A is the metal whose diffusion is * The second derivative of a is equal to the second derivative of c in dilute solution only if -da/dr- is. zero. Although theory does not require this condition, in the systems C in Fe, and Zn in Cu, dc is in fact found to be essentially zero.

Jan 1, 1950

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Jan 2, 1918