The respective contributions of mobile dislocation densities and velocities tothe deformation rate studied by transient mechanical tests

摘要

Among the transient tests used to determine activation parameters along a stress-strain curve, the method of repeated creep tests has been developed recently. It provides a microscopic activation volume characteristic of the dislocation mobility. In addition useful informations are obtained about the substructural changes which take place as a function of strain, in particular the mobile dislocation exhaustion rate. The procedure is presented, the equations and assumptions used to describe the material behaviour during the transient are exposed together with experimental assessments. In Ni_3Al polycrystals the method is applied in an attempt to determine the contribution to the strain-rate of the mobile dislocation densities and velocities in the frame of the Orowan equation. High dislocation exhaustion rates are found, in agreement with the well known Kear-Wilsdorf locking mechanism in these compounds.