A model for the anomalous mechanical properties of nickel-base L1(2) ordered alloys .1. Dislocations dynamics

A new model has been set up with the aim of explaining the mechanical properties of L1(2) nickel base alloys, in particular their anomalous increase of yield-stress with increasing temperature. In agreement with recent microscopic observations, dislocations movements are assumed to be controlled by a series of double cross-slip mechanisms between octahedral and cube planes, leading to formations and destructions of incomplete Kear-Wilsdorf locks. In this first part, the model is two-dimensional, and the splitting of superpartials into Shockley partials is not taken into account. The forces acting on leading and trailing superpartials of incomplete Kear-Wilsdorf locks have been computed, with the aim of studying the kinetics of their evolution under an applied stress. Fairly good values of the flow-stress have been obtained at low and high temperature in Ni-3 Ga, assuming that the ratio of the antiphase boundary (APB) energies in cube and octahedral planes is 0.9, and assuming that the distance of cross-slip onto the cube plane increases with increasing temperature. Copyright (C) 1996 Acta Metallurgica Inc.