روش میدان فازی در مطالعه برهم کنش استحاله های مارتنزیتی و نابجایی ها در ابعاد نانو

Abstract

In this paper, a new phase field method for the interaction between martensitic phasetransformations and dislocations is presented which is a nontrivial combination of the most advancedphase field methods to phase transformations and dislocation evolution. Some of the important points inthe model are the multiplicative decomposition of deformation gradient into elastic, transformational andplastic parts, defining a proper energy to satisfy thermodynamic equilibrium and instability conditions,including phase-dependent properties of dislocations. The system of equations consists of coupledelasticity and phase field equations of phase transformations and dislocations. Finite element methodis used to solve the system of equations and applied to study the growth and arrest of martensitic plateand the evolution of dislocations and phase in a nanograined material. It is found that dislocations playa key role in eliminating the driving force of the plate growth and their arrest which creates athermalfriction. Also, the dual effect of plasticity on phase transformations is revealed; due to dislocationspile-up and its stress concentration, the phase transformation driving force increases and consequently,martensitic nucleation occurs. On the other hand, the dislocation nucleation results in decreasing thephase transformation driving force and consequently, the phase transformation is suppressed.