Phase Transformations Induced by Severe Plastic Deformation

Abstract

Severe plastic deformation (SPD) can induce various phase transformations. After a certain strain, the dynamic equilibrium establishes between defects production by an external force and their relaxation (annihilation). The grain size, hardness, phase composition etc. in this steady-state does not depend on the initial state of a material and is, therefore, equifinal. In this review we discuss the competition between precipitation and dissolution of precipitates, amorphization and (nano)crystallization, SPD-induced accelerated mass-transfer, allotropic and martensitic transitions and formation of grain boundary phases.

Steady-state grain size in copper subjected to the different SPD modes: Ball milling (BM), High pressure torsion (HPT), Planar twist channel angular extrusion (PTCAE), Equal channel angular pressing (ECAP), ECAP+HPT, Equal channel angular pressing with following cold rolling (ECAP + CR), Simple shear extrusion (SSE), Constrained groove pressing (CGP).