Showing papers in "Acta Metallurgica in 1981"

TL;DR: In this paper, a phenomenological model is proposed to incorporate the rate of dynamic recovery into the flow kinetics, which has been successful in matching many experimental data quantitatively, and it has been shown that the proportionality between the flow stress and the square root of the dislocation density holds, to a good approximation, over the entire regime; mild deviations arc primarily attributed to differences between the various experimental techniques used.

TL;DR: In this article, a general framework is proposed to relate tip radius, interface undercooling and primary arm spacing in alloy dendrite growth, and all the growth morphologies developed between the limiting morphology at low and at high velocity are described to a first approximation, using an ellipsoid of revolution.

TL;DR: In this paper, the nucleation and growth of voids during tensile straining has been studied in spheroidized carbon-steels, and the results from the literature are compared with a simple theory of void nucleation.

TL;DR: In this article, the dendritic stability criterion measured is 2 αd 0 / VR 2 = 0.0195, where V is the growth velocity, R is the dandritic tip radius, a is the liquid thermal diffusivity, and d 0 is a capillary length defined in the text.

TL;DR: Sintering-mechanism diagrams are diagrams with axes of neck-size or density, and temperature, which identify the fields of dominance of each of the several mechanisms which contribute to sintering as discussed by the authors.

TL;DR: In this paper, the structure of deformed regions in two metallic glasses, Ni76P24 and Fe40Ni40B20, has been investigated by means of transmission electron microscopy.

TL;DR: In this paper, the authors provided experimental evidence in support of the theory that Widmanstatten ferrite formation involves the co-operative growth of mutually-accommodating plates.

TL;DR: In this paper, the authors proposed a mechanism in which differences in the diffusion coefficients of the diffusing species along the grain boundary cause a self-sustaining climb of grain boundary dislocations and motion of their associated grain boundary steps.

TL;DR: In this paper, the deformation rate of polycrystalline ceramics that contain a residual glass phase is analyzed in terms of material transport through the liquid phase, where molecules are transported and deposited in the direction of the positive normal traction gradient along the interfaces.

TL;DR: In this article, experiments have been carried out to study the development of the dendritic sidebranch structure in succinonitrile and provide insights into such fundamental problems as the origin of side-branch perturbations.

TL;DR: In this article, the phenomenological theory of martensitic transformations is applied to the various observed transformation modes in the shape memory alloy nickel-titanium and it is shown that one of the observed twinning modes can be identified as a type II mode, with the shear direction η 1 being derived from a cell edge of the parent B2 phase.

TL;DR: In this paper, the authors investigated the power-law creep behavior of polycrystalline magnesium over the temperature range from 473 to 820 K. The results show the occurrence of three different mechanisms, with the creep process depending on the testing temperature and stress level.

TL;DR: The critical resolved shear stress (CRSS) for the movement of dislocations in the alloy titanium-6Al-4V is both directionally asymmetric and dependent on pressure as discussed by the authors.

TL;DR: Localized plastic shearing was studied in single crystals of Al-2.8 wt% Cu single crystals aged to contain GP zones, θ′ and θ precipitates.

TL;DR: In this paper, the authors considered the diffusive cavitation of grain facets in circumstances for which the cavitated facets are well separated from one another, and showed that the rupture time tr, is given by the sum of two terms, one proportional to 1 Dσ ∞ (where D is the grain boundary diffusion parameter and σ∞ the stress which would act on a non-cavitated facet) and another proportional to E ∞(here E∞ is the creep rate of a similarly loaded polycrystal with uncavitated boundaries).

TL;DR: In this paper, structural structures characteristic of persistent slip bands were observed in the interior of polycrystalline copper after fatigue at low strain amplitudes, within the plateau on the cyclic stress-strain curve.

TL;DR: In this article, an elastic solution has been found for a screw dislocation near a crack in the absence of any external stresses, where the dislocation produces a stress intensity factor on the crack even without external stresses.

TL;DR: The creep behavior of Al-5% Mg divides into three distinct regions at a testing temperature of 827 K as discussed by the authors, and these three regions are consistent with viscous glide (class A), dislocation climb (class M), and Harper-Dorn creep, respectively.

TL;DR: In this article, two specially developed techniques were used to study the nucleation and growth of grain-boundary cavities in 304 stainless steel at 0.5 Tm and found that cavities nucleated heterogeneously throughout the creep history and those observed were well in their growth stage.

TL;DR: In this article, a simple theoretical approach to the general problem of diffusive growth of grain boundary cavities of both equilibrium and non-equilibrium shape in the presence of power law creep is developed.

TL;DR: In this paper, a detailed study of the mechanical properties of NiTi-based alloys is made, and a toughness minimum is observed in a certain temperature range and it is argued that this is a consequence of an interaction between deformation by stress-induced martensite and conventional plastic flow when these mechanisms operate simultaneously.

TL;DR: In this article, the PTT curve for VN precipitation in deformed austenite is located at about 25 s, indicating a similarity in the precipitation kinetics of V and Nb at equivalent Mn levels.

TL;DR: A study of the Bauschinger effect in pure copper showed that by comparison with dispersion hardened copper the effect is very small and independent of temperature This suggests that the obstacles to flow are deformable as discussed by the authors.

TL;DR: In this article, the onset of adiabatic shear instability was found experimentally to take place at a true shear strain γc = -Cn/(δτδT), where C is the volume specific heat, n is the strain hardening exponent and δτ/δ T is the slope of the temperature dependence of flow stress.

TL;DR: In this paper, the grain boundary diffusivity was evaluated as a function of temperature and the concentration behind the migrating boundaries was studied as function of the distance from the surface by microprobe measurements.

TL;DR: In this article, the incidence of martensic transformations in systems containing ZrO 2 particles (or precipitates) depends upon the size of the particles and the origin of this size effect is demonstrated to reside in the twinned or variant structure of the transformed phase, by virtue of a surface area related strain energy term.

TL;DR: In this article, the authors considered the possibility that hydrides form by a displacive or shear transformation and determined the habit planes and orientation relationships of hydride alloys.

TL;DR: In this paper, the cyclic stress-strain (CSS) curve for polycrystalline copper can be correlated with that for monocrystals, particularly in showing a plateau and a fatigue limit at an equivalent stress and strain (equivalence being expressed via Taylor's factor).

TL;DR: In this paper, the results of Monte Carlo computations of the coherent phase diagram (in the temperature-composition plane) of ordering binary alloys on an f.c. lattice were presented.