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Showing papers in "Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science in 1972"


Journal ArticleDOI
TL;DR: A new model for hydrogen-assisted cracking is presented in this article, which explains the observations of decreasing microscopic plasticity and changes of fracture modes with decreasing stress intensities at crack tips during stress-corrosion cracking and HAC of quenched-and tempered steels.
Abstract: A new model is presented for hydrogen-assisted cracking (HAC) which explains the observations of decreasing microscopic plasticity and changes of fracture modes with decreasing stress intensities at crack tips during stress-corrosion cracking and HAC of quenched-and- tempered steels The model suggests that the presence of sufficiently concentrated hydrogen dissolved in the lattice just ahead of the crack tip aids whatever deformation processes the microstructure will allow Intergranular, quasicleavage, or microvoid coalescence fracture modes operate depending upon the microstructure, the crack-tip stress intensity, and the concentration of hydrogen The model unifies several theories but shows how the stress-sorption and lattice embrittlement models are unnecessary The model shows that planar pressure effects are necessary at low stress intensities and are necessary only to augment the driving force from the applied loads The basic hydrogen-steel interaction appears to be an easing of dislocation motion or generation, or both

1,070 citations


Journal ArticleDOI
TL;DR: In this article, the initiation of a crack in a specimen under tensile or compressive stresses is treated from the point of view of perturbation analysis, where a surface distortion is Fourier analyzed into a series of waves and the amplitude response of a single component of varying frequency is theoretically investigated.
Abstract: The initiation of a crack in a specimen under tensile or compressive stresses is treated from the point of view of perturbation analysis. A surface distortion is Fourier analyzed into a series of waves and the amplitude response of a single component of varying frequency is theoretically investigated. The response of the individual components yields a Griffith-type criterion for wave amplitude growth. The model is applied to alloy systems undergoing stress corrosion cracking via surface diffusion.

740 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used a Couette type viscometer to study the rheological behavior of Sn-15 pct Pb alloy in the solidification range.
Abstract: Rheological behavior of Sn-15 pct Pb alloy in the solidification range has been investigated using a Couette type viscometer. In samples partially solidified before shearing, deformation is localized and primarily intergranular. Samples containing more than about 0.15 fraction solid exhibit an “apparent yield point” which is on the order of 106 dyne per sq cm and increases with increasing fraction solid. When shearing is conducted continuously while the alloy is cooled from above the liquidus to the desired final fraction solid, shear stresses required for flow are reduced by about three orders of magnitude. The solid-liquid mixture now behaves as a fluid slurry. Structural examination shows that shear takes place throughout the cross section of the specimen and that the solid is present as a fine grained particulate suspension. Flow behavior can be described by a viscosity which depends on fraction solid, decreases with increasing shear rate and exhibits hysteresis when shear rate is changed. For shear rates of 200 sec−1, at 0.40 fraction solid, viscosity is about 5 poise which is equivalent to that of heavy machine oil at room temperature. The fact that the slurry is highly fluid at large fractions solid suggests potential applications in new and existing metal casting processes.

701 citations


Journal ArticleDOI
TL;DR: In this paper, time-temperature-precipitation diagrams were determined between 400° and 900°C for up to 3000 hr as a function of carbon content, solution treatment temperature, and cold work.
Abstract: Although Type 316 austenitic stainless steel is widely used in steam generating plants and nuclear reactors the knowledge about aging reactions, nature of precipitates, and precipitation kinetics during high temperature exposure is limited. Time-temperature-precipitation (TTP) diagrams were determined between 400° and 900°C for up to 3000 hr as a function of carbon content, solution treatment temperature, and cold work. The nucleation and growth phenomena, morphology, and composition of the various carbide (M23C6, M6C) and intermetallic phases (σ, χ, η were determined. The complex sequence of phase instabilities can be explained on the basis of the carbon content, effect of molybdenum and chromium on the carbon solubility, thermodynamic stability of the phases, and the kinetics of the various precipitation reactions.

658 citations


Journal ArticleDOI
TL;DR: In this article, the tensile flow and fracture behavior of three Pdo.8Sio2-based alloys in the glassy, "micro-crystalline, and fully crystalline condition has been studied.
Abstract: The tensile flow and fracture behavior of three Pdo.8Sio2-based alloys in the glassy, “microcrystalline,” and fully crystalline condition has been studied. The glassy alloys flow plastically to a total strain of approximately 0.5 pct e, and exhibit proportional limit stresses of approximatelyE x 10~2 whereE is Young’s modulus. This plastic flow is accompanied by the formation of shear deformation bands on the specimen surfaces. Fully crystalline alloys are extremely brittle and fracture via intergranular cracking. Fracture surfaces of the amorphous and “microcrystalline” alloys are inclined at 45 deg to the tensile axis and exhibit two morphologically distinct zones. One zone is relatively featureless while the other contains a “river” pattern of local necking protrusions. Detailed comparison of opposing surfaces indicates that fracture is preceded by large local plastic shear which produces the smooth zone while the local necking pattern is produced during rupture. These observations form the basis for the hypothesis that plastic flow in the glassy material occurs via localized strain concentrations and that fracture is initiated by catastrophic, “adiabatic” shear.

370 citations


Journal ArticleDOI
TL;DR: In this article, the intrinsic stacking fault energy in the austenite drastically increases with temperature in all the chromium-bearing alloys investigated, which is consistent with the observed influence of temperature on the appearance of twinning or e martensite during plastic deformation.
Abstract: Martensitic transformations induced by plastic deformation are studied comparatively in various alloys of three types: Fe-30 pct Ni, Fe-20 pct Ni-7 pct Cr, and Fe-16 pet Cr-13 pct Ni, with carbon content up to 0.3 pct. For all these alloys the tensile properties vary rapidly with temperature, but there are large differences in the value of the temperature rangeM s toM d, which strongly increases with substitution of chromium for nickel or with carbon addition. Using the node method, it is found that the intrinsic stacking fault energy in the austenite drastically increases with temperature in all the chromium-bearing alloys investigated. This variation is consistent with the observed influence of temperature on the appearance of twinning or e martensite during plastic deformation. Very different α’ martensite morphologies can result from spontaneous and plastic deformation induced transformations, especially in Fe-20 pct Ni-7 pct Cr-type alloys where platelike and lath martensites are respectively observed. As in the case of e martensite, the nucleation process is analyzed as a deformation mode of the material, using a dislocation model. It is then possible to account for the morphology of plastic deformation induced α’ martensite in both Fe-20 pct Ni-7 pct Cr and Fe-16 pct Cr-13 pct Ni types alloys and for the largeM s toM d range in these alloys.

366 citations


Journal ArticleDOI
TL;DR: In this article, the effects of alloying elements on the properties of iron are studied, including lattice parameters, elastic constants, the effect of temperature on strength, solid solution strengthening and softening, work hardening, strain aging, hot working and toughness.
Abstract: The new results of an extensive study of the effects of alloying elements upon the properties of iron are presented, including lattice parameters, elastic constants, the effect of temperature on strength, solid solution strengthening and softening, work hardening, strain aging, hot working and toughness.

328 citations


Journal ArticleDOI
TL;DR: A critical review of published data provides a fairly accurate knowledge of the thermodynamic properties of all of the phases of the system Fe-C that are stable or metastable at atmospheric pressure as discussed by the authors.
Abstract: A critical review of published data provides a fairly accurate knowledge of the thermodynamic properties of all of the phases of the system Fe-C that are stable or metastable at atmospheric pressure. Selected data are shown as tables and equations. A proposed phase diagram differs only slightly from others recently published but has the following features. Peritectic compositions and the α-γ equilibrium are shown to agree with measured values of the activity of iron in the solid and liquid solutions and the thermodynamic properties of pure iron. Of all the reported carbides of iron only two may be studied under equilibrium conditions. The solubilities of cementite and of χ-carbide in α-Fe are deduced from measured equilibria. Both are metastable at all temperatures with respect to graphite and its saturated solution in iron. The χ-carbide becomes more stable than cementite below about 230° Certain published data on e-carbide permit an estimate of its free energy as a precipitate during the aging process.

311 citations


Journal ArticleDOI
R. L. Miller1
TL;DR: In this article, a variety of alloy steels with grain sizes in the range 0.3 to 1.1 μ were obtained in manganese and nickel steels by annealing 1 to 400 hr at temperatures between 450° and 650°C (840° to 1200°F).
Abstract: Ultrafine-grained microstructures can be developed in a variety of alloy steels by coldworking followed by annealing in theα +γ region. Because the annealing temperatures are relatively low and the recrystallized structure is two-phase, grain growth is restricted. Specimens with grain sizes in the range 0.3 to 1.1 μ.m (ASTM 20 to 16) were obtained in manganese and nickel steels by annealing 1 to 400 hr at temperatures between 450° and 650°C (840° to 1200°F). The expected improvement in yield strength through grain refinement was observed in almost all alloys. Other tensile properties depend on factors such as grain size, austenite stability, and specimen geometry, that determine which of three types of plastic behavior will occur. Transformation of austenite during straining improves the mechanical properties of ultrafine-grained specimens.

311 citations


Journal ArticleDOI
TL;DR: In this article, the early stages of cellular precipitation in quenched and aged alloys were investigated using light and electron microscopy observations of the early stage of cellular formation. But the early development of cellular cells was not investigated.
Abstract: The morphology of cellular precipitation in a Cu-9.5 at. pet In alloy has been investigated by light and electron microscopy. Both cellular and general precipitation were observed to occur simultaneously in quenched and aged alloys while only cellular precipitation was observed to occur in isothermally aged alloys. Because of the presence of wide, solute rich, precipitate free zones in the vicinity of grain boundaries in the quenched and aged alloys, the early development of cellular precipitation was found to be identical for both types of heat treatment. From light and electron microscopy observations of the early stages of cellular precipitation a mechanism for the formation of cells was developed. At the start of aging, the unoccupied grain boundary begins to migrate under the influence of grain boundary migration forces as if it were in a single phase alloy. As the boundary migrates, solute segregates along it to form allotriomorphs which pin the boundary. The boundary continues to migrate and bows between the simultaneously forming allotriomorphs. With further aging, the allotriomorphs lengthen following the bowing boundary and the allotriomorphs become the initial precipitate lamellae of the developing cell as a steady-state lamellar structure develops. Assuming that the critical step in the development of a cell is the ability of the boundary to bow between the initial allotriomorphs, a criterion for the occurrence of cellular precipitation was developed.

190 citations


Journal ArticleDOI
TL;DR: Growth theories for the lamellar eutectoid transformation are reviewed from a free energy point of view in order to form a background for an examination of the various treatments of growth during discontinuous precipitation as discussed by the authors.
Abstract: Growth theories for the lamellar eutectoid transformation are reviewed from a free energy point of view in order to form a background for an examination of the various treatments of growth during discontinuous precipitation. The shortcomings of Cahn’s theory of discontinuous precipitation are pointed out and the treatment based upon the individual consideration of growth conditions for the two phases is discussed, with particular emphasis on how the total free energy available to drive the reaction is divided into many parts which are used for various purposes. New sets of calculations are presented in order to demonstrate the effect of free energy losses due to boundary friction and volume diffusion. The effect of coherency stresses in the parent grain is shown to decrease the free energy loss due to volume diffusion and may thus provide a driving force for grain boundary movement.

Journal ArticleDOI
TL;DR: In this article, a critical appraisal of theory and experiments for both isothermal and forced velocity pearlite is presented, and a new perturbation procedure for definition of the optimal steady-state spacing is presented.
Abstract: A critical appraisal of theory and experiments for both isothermal and forced velocity pearlite is presented. It is concluded for binary systems that both the theoretical models for volume diffusion and boundary diffusion control are well-advanced and adequate for the purposes of experimental test. However, some ambiguity remains in the boundary diffusion model with respect to the thermodynamics of the boundary ”phase” region, so it is still not possible to predict absolute rates of transformation. The theoretical problem for ternary pearlites is also well understood, although rigorous theory seems intractable. A new perturbation procedure for definition of the optimal steady-state spacing is presented and amplified for both isothermal and forced velocity pearlite, and for both volume and boundary diffusion models. In terms of the critical spacing Sc for isothermal pearlite and the spacing at minimum undercooling Sm for forced velocity pearlite the predicted stability points are as follows: {fx2777-1} For isothermal pearlite these perturbation results correspond closely to the state of maximum entropy production rate while for forced velocity pearlite the correspondence is also satisfactory. A detailed analysis of the data leads us to reaffirm the author’s conclusions that the eutectoid reactions in Cu-12 pct Al and some related ternary alloys reported by Asundi and West are controlled by volume diffusion and that the eutectoid reaction in Al-78 Zn reported by Cheetham and Ridley is controlled by boundary diffusion. We conclude further after careful analysis that the pearlite reaction in Fe-0.8 C is controlled for the higher temperatures by volume diffusion of carbon in austenite. We are also led to state that the pearlite transformations in Fe-C-Mn and Fe-C-Ni occur for the most part in a nopartition regime and are therefore controlled by volume diffusion of carbon in austenite, while the transformations in Fe-C-Cr and Fe-C-Mo, being forced by thermodynamics to sustain partition of chromium and molybdenum, are controlled by phase boundary diffusion of the latter elements. nt]mis|M. P. PULS, formerly Postdoctoral Fellow, Department of Metallurgy and Materials Science, McMaster University, Hamilton, Ontario, Canada

Journal ArticleDOI
L. F. Coffin1
TL;DR: Push-pull fatigue tests have been conducted on several materials at various frequencies and temperatures in air and high vacuum (10−8 torr) and the fatigue life determined in terms of the cyclic plastic strain this article.
Abstract: Push-pull fatigue tests have been conducted on several materials at various frequencies and temperatures in air and high vacuum (10−8 torr) and the fatigue life determined in terms of the cyclic plastic strain. In contrast to a changing exponent of the Coffin-Manson law with increasing temperature in air, in high vacuum this exponent is found to remain nearly constant at a value of about 0.5. Further, the temperature sensitivity of this exponent and of life at a specific plastic strain range in high vacuum is slight. Pronounced plastic instability (specimen shortening and fattening) was observed for the ductile metals investigated and crack nucleation was retarded. In all cases crack propagation was transgranular in vacuum. It is concluded that for the materials, temperature, and frequencies investigated, the degradation of fatigue life at elevated temperature is due to environmental enhancement of intergranular fracture. Materials investigated include A286 at room temperature and 593°C, nickel A at 550°C, 304 stainless steel at 816°C and 7075T6 aluminum alloy.

Journal ArticleDOI
TL;DR: In this paper, the authors considered various deformation mechanisms for superplastic deformation and showed that grain boundary sliding is the major deformation mode, but the sliding rate should be governed by the lesser rate of dislocation creep within the grains.
Abstract: Under various conditions of stress and temperature various deformation mechanisms could be rate-controlling for superplastic deformation. In general at low stresses diffusion creep should be rate-controlling. At temperatures between approximately 40 and 65 pct of the absolute melting point grain boundary diffusion should be the dominant diffusion path while at higher temperatures volume diffusion should dominate. At intermediate stresses, grain boundary sliding should be the major deformation mode, but the sliding rate should be governed by the lesser rate of dislocation creep within the grains. At temperatures between 40 and 65 pct of the melting point, the rate of dislocation creep should be controlled by dislocation pipe diffusion, while at higher temperatures volume diffusion should be ratecontrolling. At high stresses the superplastic effect of unusually large tensile extensibility should diminish due to the greater possibility of work-hardening processes such as dislocation cell, tangle, and pile-up formation.


Journal ArticleDOI
TL;DR: In this article, an analytical model consisting of an elastic crack with a regular array of tractions representing the ligaments supporting the view that ligaments are the principal source of brittle crack propagation resistance in the steels was presented.
Abstract: Studies of the unstable propagation and arrest of brittle fractures were conducted on four steels: plain carbon steel, 3 pct Si steel, A-517, and 4340. Unstable fractures were initiated in double-cantilever-beam test specimens by forcing a wedge between the two beams under compression. These fractures propagate at essentially constant wedge opening displacement and can be made to arrest within the confines of the specimen. The strain energy stored in the specimen at the onset of propagation was varied systematically by changing the root radius of the starting slot. The experiments show that Ka, the stress intensity at arrest, is not a materials constant but depends on the strain energy stored in the specimen. Values of άrcR, the average energy dissipation rate during propagation, calculated for the four steels, are in the range23- GIc ≲ άcrR ≲ G{Ic}. Detailed metallographic examinations show that brittle fractures appear highly segmented on interior sections, but that the individual segments are interconnected. This morphology is attributed to isolated, difficult-to-cleave regions, comparable in size to the grains, which are bypassed and remain unbroken at relatively large distances behind the crack front. Etching studies conducted on a silicon steel reveal that the plastic deformation attending crack propagation is largely confined to the plastic stretching of the ligaments behind the crack front. Increases in the size, number, and toughness of the ligaments with temperature coincide with the brittle-to-ductile transition. An analytical model consisting of an elastic crack with a regular array of tractions representing the ligaments supports the view that the ligaments are the principal source of brittle crack propagation resistance in the steels.

Journal ArticleDOI
TL;DR: In this article, the microstructural changes during the α→ FeAl, FeAl → Fe3Al, and α→Fe3Al transitions were studied by transmission electron microscopy.
Abstract: The microstructural changes during the α→ FeAl, FeAl → Fe3Al, and α→ Fe3Al transitions were studied by transmission electron microscopy. The ordering of ferromagnetic α was observed to occur in a classical manner by the nucleation and growth of particles of the FeAl or Fe3Al type phases. However, the ordering of paramagnetic α to FeAl and paramagnetic FeAl to Fe3Al occurred by a mechanism which showed many of the characteristics expected of a second or higher degree transition. These included critical point fluctuations in the degree of long-range order which also appeared to be greater in the vicinity of antiphase domain boundaries. The FeAl phase was also observed to partially disorder in the initial stages of the FeAl → α + FeAl transition and this effect appears to account for the anomalous magnetic behavior of some FeAl alloys.

Journal ArticleDOI
TL;DR: In this article, a systematic description of cellular reactions with special account to the discontinuous precipitation is given, including the constitutional, nucleation, and other conditions for its occurrence; the role of grain boundaries, dislocations, and vacancies for the mechanism; the effect of continuous precipitation before discontinuous rainfall; multiple discontinuous reactions; effects of grain boundary structure, third elements, and external stress; reactions in highly defect crystals and amorphous solids.
Abstract: A systematic description is given of cellular reactions with special account to the discontinuous precipitation. The following special aspects of this reaction are discussed: The constitutional, nucleation, and other conditions for its occurrence; the role of grain boundaries, dislocations, and vacancies for the mechanism; the effect of continuous precipitation before discontinuous precipitation; multiple discontinuous reactions; effects of grain boundary structure, third elements, and external stress; reactions in highly defect crystals and amorphous solids. It is shown that all phenomena can be understood either by effects on driving force or mobility of the reaction front.

Journal ArticleDOI
TL;DR: The temperature dependence of the long range (internal) and thermally activated components of the flow stress have been measured by a stress relaxation technique over the temperature range 200 to 550 K in α titanium containing five different levels of oxygen.
Abstract: The temperature dependence of the long range (internal) and thermally activated components of the flow stress have been measured by a stress relaxation technique over the temperature range 200 to 550 K in α titanium containing five different levels of oxygen. In addition, the dislocation arrangements have been studied using thin foil electron microscopy techniques. In the higher oxygen materials it has been found that a transition from wavy to planar slip occurs towards lower temperatures. The internal stress varies more strongly with temperature than would be predicted by the temperature dependence of the elastic modulus; simultaneously, the thermally activated component of the flow stress (t*) obtained as the difference between the flow and internal stresses, goes through a maximum at the temperature where the internal stress (Tint) becomes strongly temperature dependent. An increase in t* and rise of Tint accompany the onset of planar slip.

Journal ArticleDOI
TL;DR: In this paper, the influence of molybdenum on lattice parameters was investigated in wrought nickel-base superalloys containing about 14 at.pct Cr and 6-1/2, 9, or 12 at. pct Ti alloys.
Abstract: The influence of 1, 3, and 5 at. pct Mo on the γ’precipitate has been studied in experimental wrought nickel-base superalloys containing about 14 at. pct Cr and 6-1/2, 9, or 12 at. pct Al, or 2 at. pct Al plus 4 at. pct Ti. Concentrations of all other elements were quite low to limit the observed effects to those of molybdenum alone. Molybdenum markedly increases the γ’ solvus temperature, as determined by the sensitive and relatively simple technique of differential thermal analysis; correspondingly, the weight fraction of γ’ increases with molybdenum additions for a given aging treatment. Molybdenum dissolves extensively in the γ’of the titanium-free alloys, but it dissolves to a considerably smaller extent in the γ’of the titanium-bearing alloys. Molybdenum substitutes for chromium in y’, but does not alter the aluminum or titanium contents of this phase. Lattice parameters of both the matrix and the γ’are increased markedly by molybdenum, in proportion to the molybdenum contents of these phases. The resulting effects on lattice-parameter mismatch correlate rather well with observed γ’morphology, which tends to change from spheroidal to cuboidal in titanium-free alloys, and from cuboidal to spheroidal in 2 at. pct Al-4 at. pct Ti alloys, as molybdenum is added to these alloys.

Journal ArticleDOI
TL;DR: In this paper, the authors applied the directional solidification technique to investigate the complicated solidification sequence in a commercial austenitic stainless steel which was known to yield a primary precipitation of § ferrite when cast into a 5 tons ingot.
Abstract: The directional solidification technique was applied in order to investigate the complicated solidification sequence in a commercial austenitic stainless steel which was known to yield a primary precipitation of § ferrite when cast into a 5 tons ingot. Three stages of solidification were found. The first precipitation of § ferrite was interrupted by precipitation of austenite and at the end of the solidification there was a transition back to precipitation of § ferrite. The competition between the first two stages is affected by the cooling rate and the nitrogen content. The precipitation of austenite from the melt results in the usual coring whereas o ferrite forms with a very homogeneous composition, presumably due to rapid diffusion in this phase. On cooling austenite forms from the § ferrite and this reaction also results in coring, presumably due to rapid diffusion in § ferrite.

Journal ArticleDOI
TL;DR: In this paper, the activity of carbon in austenitic Fe-Mo-C, Fe-Cr-C and Fe-V-C alloys has been studied by equilibration with controlled CH4-H2 atmospheres at temperatures in the range 850° to 1200°C.
Abstract: The activity of carbon in austenitic Fe-Mo-C, Fe-Cr-C, and Fe-V-C alloys has been studied by equilibration with controlled CH4-H2 atmospheres at temperatures in the range 850° to 1200°C. The observations included a number of compositions in the two-phase fields, γ + carbide. Equations are given for the activity coefficient of carbon as a function of temperature and composition in the austenite field and from these the other thermodynamic properties of the solution may be computed as desired. The phase boundaries γ/γ + carbide were determined by breaks in the isoactivity lines. This was supplemented in the case of Fe-Mo-C alloys by metallographic linear analysis of equilibrated samples. The results confirm certain published phase diagrams and discredit others.

Journal ArticleDOI
TL;DR: In this paper, a method for estimating the internal sliding from surface measurements, and an analysis is made of detailed results published for α iron for grain boundary sliding during creep, is presented.
Abstract: In studies of grain boundary sliding during creep, it is necessary to distinguish between the strain due to sliding in the bulk of the specimen and the strain occurring at the surface. In general, these quantities are not the same, although the difference depends on the configuration of the surface grains. Methods are suggested for estimating the internal sliding from surface measurements, and an analysis is made of detailed results published for α iron.

Journal ArticleDOI
TL;DR: In this paper, tensile and compressive stress-strain curves were obtained for several types of microstructures in a variety of steels, including Widmanstatten ferrite-pearlite and ultrafine-grained martensite.
Abstract: Tensile and compressive stress-strain curves were obtained for several types of microstructures in a variety of steels. The strength-differential effect, previously found in martensitic structures, was present in lower, intermediate, and upper bainite and in Widmanstatten ferritepearlite as well as in ultrafine-grained martensite. An equiaxed ferrite-pear lite structure showed no strength differential. The strength differential in martensite increased as test temperature was decreased below room temperature. In several series of tests, the same specimen design was used in tension and in compression to eliminate possible strength variations due to variations in specimen preparation. Several theories which have been proposed for the strength-differential effect are discussed with respect to the present results, and it is shown that most of the previous suggestions are invalid.

Journal ArticleDOI
TL;DR: In this paper, the diffusion coefficient of pure platinum, calculated from the time lag to reach a steady state flux, is: {065-01} in the temperature range of 1435∮ to 1504°.
Abstract: The diffusivity and solubility of oxygen in metal specimens were determined from measurements of permeation through thin wall tubes containing oxygen and heated by electrical resistance. The permeating oxygen desorbed in vacuum as monoatomic oxygen and the flux was monitored mass-spectrometrically. A known helium leak rate and experimentally-determined sensitivities of the two gases were used for flow calibration. The diffusion coefficient of oxygen in pure platinum, calculated from the time lag to reach a steady state flux, is: {fx065-01} in the temperature range of 1435∮ to 1504°. The solubility of oxygen in pure platinum was obtained from the steady-state flux using the previously determined diffusivity. The solubility is proportional to p1/2O2 and at 1 atm of oxygen the solubility is: CsO = (0.2 ± 0.1) × 1012 exp {fx065-02}, wt pct. Small amounts of nickel, less than required for internal oxidation, had a negligible effect on the oxygen solubility and diffusivity in platinum alloys.

Journal ArticleDOI
TL;DR: In this article, the authors used a model in which compatibility is maintained between the matrix and precipitate platelets, the platelets both deforming and rotating, and predicted that normally weak orientations are strengthened more by precipitation than normally hard orientations.
Abstract: Plane-strain compression tests were made on age-hardened Al-4 pct Cu single crystals of various orientations. The resulting stress-strain curves showed much less anisotropy than would be expected from single-phase crystals under the same conditions of testing. The data are explained by a model in which compatibility is maintained between the matrix and the precipitate platelets, the platelets both deforming and rotating. This model predicts that normally weak orientations are strengthened more by precipitation than normally hard orientations.

Journal ArticleDOI
TL;DR: In this article, the effect of microstructures on the strength differential (SD) of high-strength steels was analyzed, i.e., the strength level difference between the tensile and compressive flow curves.
Abstract: Room temperature tensile and compressive true stress-true strain curves of various high strength steels (quenched and tempered 4340 steel, 410 martensitic stainless steel, and H-11 steel; and aged 300-grade 18 Ni maraging steel) were analyzed to determine the effect of the various microstructures, on what has been termed the strength differential (SD),i.e., the strength level difference between the tensile and compressive flow curves. Care was taken to insure that the compressive deformation was homogeneous. Regardless of the amount of plastic deformation, the quenched and tempered steels exhibited a higher flow stress in homogeneous compressive deformation than for tensile deformation. The extent of the SD was dependent on tempering temperature. This observation is consistent with what others have observed regarding yield strength behavior of quenched and quenched-and-tempered steels. Despite the low carbon content, aged maraging steel also showed a greater resistance to homogeneous compressive deformation. Metallographic examination of the maraging steel revealed the banding that is indicative of segregation. However, homogenization had little effect on the SD despite a change in austenite grain size, reverted austenite content, and the austenite-to-martensite transformational strains shown by Goldberg to be present in segregated material.

Journal ArticleDOI
TL;DR: In this article, the embrittlement of vanadium and tantalum by hydrogen has been investigated with the ultimate goal being to answer three specific questions concerning ductility behavior in different temperature ranges.
Abstract: The embrittlement of vanadium and tantalum by hydrogen has been investigated with the ultimate goal being to answer three specific questions concerning ductility behavior in different temperature ranges. Torsion pendulum internal friction and another technique using the torsion pendulum as well as visual observations have been used to establish the solid solubility curve in the V-H and the Ta-H systems. The primary variables studied in this work were tensile strain rate, test temperature and hydrogen content. The results have been analyzed and tentative hypotheses have been set forth to explain the ductility behavior of the hydrogen charged metals.

Journal ArticleDOI
TL;DR: In this paper, the authors studied the environmental hydrogen embrittlement of a Ti-6 Al-4 alloy as a function of test displacement rate and variations in alpha-beta microstructure.
Abstract: Study of environmental hydrogen embrittlement of a Ti-6 Al-4 alloy as a function of test displacement rate and of variations in alpha-beta microstructure Embrittlement in low-pressure (about 1 atm) gaseous hydrogen was inversely dependent on test displacement rate and strongly dependent on microstructure At a given displacement rate, microstructures having a continuous alpha-phase matrix were less severely embrittled than those having a continuous beta-phase matrix Further, brittle fracture occurred in the former microstructures by transgranular cleavage and in the latter microstructures by intergranular separation These observations are consistent with previous studies made on slow strain-rate embrittlement of hydrogen-charged titanium alloys and are explained in terms of relative hydrogen transport rates within the alpha-phase and beta-phase titanium

Journal ArticleDOI
TL;DR: In this article, the relative effects of pearlite and spherodite on ductile, cleavage, and fatigue failure are summarized, and it is shown that neither the cleavage strength nor the fatigue endurance limit appear to depend directly on cementite content per se.
Abstract: The relative effects of pearlite and spherodite on ductile, cleavage, and fatigue failure are summarized. Neither the cleavage strength nor the fatigue endurance limit appear to depend directly on cementite contentper se. Spherodized steels cleave less readily than ferrite/pearlite steels. Ductile fracture resistance is lowered considerably by both types of cementite, pearlite being more deleterious. Ferrite/pearlite steels appear to exhibit slower fatigue crack growth rates at low stress intensity levels than high strength steels. At high stress intensity levels the behavior is reversed. Slip-incuded cracking of carbide lamellae appears easier than that of spherodized carbides. In ductile fracture situations the crack spreads progressively through a pearlite colony via preferential cracking of carbides and rupture of the intervening ferrite accompanied by large local shear strains. Fatigue fracture proceeds with formation of frequent branches, preferentially along the pearlite colony interface.