Relaxation of the Bauschinger effect by thermal treatment on tempered martensitic steels

Abstract

The relaxation of the Bauschinger effect was studied through tension–compression tests with the application of a heat treatment after tension and before compression. Two contributions to the back stresses causing Bauschinger were identified, one responsible for transient deformation and other responsible for persistent softening associated with the polarization of the dislocation structure. Their relaxation kinetics is quite different; the first contribution relaxes at temperatures below 500 ◦C following an ageing kinetics. The second relaxes following the recovery kinetics of the material. To support this statement, crystal based modeling of the evolution of the dislocation structure during the deformation process and thermal treatment was performed. Hardening/softening was accounted by the variations of the critical resolved shear stress (CRSS) of each slip system with the straining history under the Taylor assumption. Recovery of the dislocation densities was introduced by a factor obtained from forward straining recovery tests.