Simulation of Dislocation and Transformation Plasticity in Shape Memory Alloys

摘要

A model of deformation of shape memory alloys has been developed. It takes into account deformation due to the phase transformation and plastic deformation, produced by an external stress or by inter-phase stresses (micro- plastic deformation at accommodation of martensite). Constitutive equations are formulated basing on the background general microstructural approach named structure-analytical theory of strength. Equations describing variation of martensite content, phase and plastic deformations are formulated on the micro- level with the account of the symmetry and kinetics of these processes, appearance of internal stresses. Macroscopic quantities are obtained by averaging. Two variants of the model have been developed for alloys of Ti-Ni and Fe-Mn-Si types. Stress-strain and strain-temperature dependencies including strain accumulation at thermal cycling and two-way shape memory effect have been described. An account of inter-grain stresses allowed to model some finer effects. A series of experiments has been carried out to study the influence of active plastic deformation on shape memory effects in TiNi alloys.