Plastic deformation of crystals: analytical and computer simulation studies of dislocation glide

Abstract

The plastic deformation of crystals is usually accomplished through the motion of dislocations. The glide of a dislocation is impelled by the applied stress and opposed by microstructural defects such as point defects, voids, pre cipitates and other dislocations.The planar glide of a dislocation through randomly distributed obstacles is considered. The objective of the present research work is to calculate the critical resolved shear stress (CRSS) for athermal glide and the velocity of the disloca tion at finite tempereature as a function of the applied stress and the nature and strength of the obstacles.Dislocation glide through mixtures of obstacles has been studied analyti cally and by computer simulation. Arrays containing two kinds of obstacles as well as square distribution of obstacle strengths are considered. The critical resolved shear stress for an array containing obstacles with a given distribution -ivof strengths is calculated using the sum of the quadratic mean of the stresses for the individual obstacles and is found to be in good agreement with the com puter simulation data.Computer simulation of dislocation glide through randomly distributed obstacles containing up to 10 6 obstacles show that the CRSS decreases as the size of the array increases and approaches a limiting value. Histograms of forces and of segment lengths are obtained and compared with theoretical predictions.Effects of array shape and boundary conditions on the dislocation glide are also studied.Analytical and computer simulation results are compared with experimen tal results obtained on precipitation-, irradiation-, forest-, and impurity clusterhardening systems and are found to be in good agreement.

A new crystal plasticity framework to simulate the large strain behaviour of aluminum alloys at warm temperatures

“…Decades of research have been conducted on the understanding of the behaviour of dislocation propagation and mean slip distance (Taylor 1934;Cottrell and Stokes 1955;Basinski 1959;Foreman and Makin 1967;Louat 1978;Diak et al 1998;Park and Niewczas 2008;Altintas 2011). What has been concluded is that, upon initial straining is nearly equal to the inter-obstacle spacing and increases during deformation to a length directly related to cell size.…”

“…An estimation of is possible through a quantitative analysis of the advance of a dislocation through a random array of obstacles (Friedel, 1964;Makin, 1966, 1967;Kocks, 1967;Altintas, 1978). The analysis can be derived from the Altintas (1978) diagram of randomly dispersed point obstacles, shown in Figure 1. The algebraic relationships between the interobstacle spacing , dislocation arc radius , height of new sector (assumed here that , mean slip distance), which are determined by the strength of obstacle parameter such that .…”