Abnormal subgrain growth in a dislocation-based model of recovery

TL;DR

This study uses dislocation dynamics simulations to explore subgrain growth during recovery, revealing abnormal coarsening behavior and the effects of temperature on growth kinetics, aligning with recent experimental observations.

Contribution

It introduces a dislocation-based model incorporating climb and thermal noise to simulate subgrain growth, highlighting abnormal coarsening and deviations from Holt's relation.

Findings

Growth follows power-law kinetics independent of climb mobility

Larger subgrains grow faster than smaller ones (abnormal coarsening)

Holt's relation does not hold during coarsening

Abstract

Simulation of subgrain growth during recovery is carried out using two-dimensional discrete dislocation dynamics on a hexagonal crystal lattice having three symmetric slip planes. To account for elevated temperature (i) dislocation climb was allowed and (ii) a Langevin type thermal noise was added to the force acting on the dislocations. During the simulation, a random ensemble of dislocations develop into subgrains and power-law type growth kinetics are observed. The growth exponent is found to be independent of the climb mobility, but dependent on the temperature introduced by the thermal noise. The in-depth statistical analysis of the subgrain structure shows that the coarsening is abnormal, i.e. larger cells grow faster than the small ones, while the average misorientation between the adjacent subgrains remains nearly constant. During the coarsening Holt's relation is found not to be fulfilled, such that the average subgrain size is not proportional to the average dislocation spacing. These findings are consistent with recent high precision experiments on recovery.