Potentiel pseudoelastique et plasticite de transformation martensitique dans les monoet polycristaux metalliques

Abstract

The subject of this study is the behaviour of single and polycrystals undergoing a thermoelastic martensitic transformation which leads to creation of different variants of martensite. The overall behaviour is the superposition of contributions from the phase transformation and from other mechanisms of deformation—for example plasticity. Two classes of behaviour can then be distinguished: pure transformation plasticity exclusively due to phase transformation (the martensitic transformation); and coupled transformation plasticity in which plastic flow couples with the intrinsic (martensitic) contribution. For the first, a thermomechanical analysis based on the Gibbs-free energy gives the transformation criterion and the associated flow rule. The analysis, for the case of a single crystal, introduces the interaction matrix between the variants of the created martensite. This matrix determines the different classes of interaction between the variants. A phenomenological constitutive relation (transformation threshold for the rule of strain hardening) has been proposed for a polycrystal. It is similar to that proposed by Drücker and Prager. The results of theoretical analyses have been compared with the experimental data, for both single and polycrystals, obtained for pseudoelastic alloys of the Cu-Zn-Al type.