High temperature grain shrinkage under different pre-strains: a phase-field-crystal study

Abstract

In this work, we use the phase-field-crystal method to study high temperature grain shrinkage. A circular grain embedded in a symmetric tilt planar grain boundary (GB) is constructed as the simulation system. Misorientation angle of the circular GB has influence on the specific evolution process. Difference between low and high misorientation angle systems is explored. In low misorientation angle system, grain shrinkage is first enabled by dislocation migration. Then dislocation rearrangement process in trijunction areas triggers the further shrinkage of inner grain. The free energy density (FED) curve has a rising stage during the overall decline process. For high misorientation angle system, dissociation and recombination reaction of dislocations is the primary way to shrink inner grain. The FED curve monotonically declines. Additionally, we apply pre-strain to simulation system. The influence of pre-strain on grain shrinkage in low and high misorientation angle systems is also investigated. When pre-strain is relatively small, the evolution process has no difference with unstrained situation, but grain shrinkage is impeded. Further increasing pre-strain, dislocations are emitted from circular GB. Grain shrinkage is accelerated and the inner grain eventually disappears prior to the grain disappearance in unstrained system. There exists a critical pre-strain to control the emission of dislocations.