Effect of strain and high temperature annealing on grain boundary characteristic distribution of compositionally complex Fe-Mn-Al-C-Cr steel

Abstract

The optimization of the grain boundary of compositionally complex Fe-Mn-Al-C-Cr Steel was realized by low strain (≤5%) and annealing at 1100 ℃ for 30 min. The fraction of coincident site lattice (CSL) boundaries has reached 82.9%. Larger strain (≥10%) promoted the recrystallization of grains, leading to failure of the optimization of grain boundaries, and the grains presented a bimodal distribution. The stress mainly concentrated on random grain boundaries (RGBs) and twin boundaries, which made part of twin boundaries deviate from their ideal orientation. Low strain and annealing promoted the faceting-roughening transition to form incoherent twin grain boundaries with various morphologies. The incoherent twin boundaries also tended to the ideal orientation and were easier to migrate due to their higher energy, resulting in the formation of grain clusters with Σ3n orientation relationship. The two signs of realizing the optimization of grain boundaries were large-sized grain clusters and broken RGBs.