Nucleation mechanisms of dynamic recrystallization in austenitic steel alloy 800H

Grain boundary character evolution during dynamic recrystallization (DRX) in a non-equiatomic Fe40Mn40Co10Cr10 high entropy alloy has been examined systematically through single pass hot rolling of 30, 50 and 70 pct reduction. It was observed that the extent of DRX is highly dependent upon the hot rolling reduction. The recrystallization area fraction was considerably higher at 50 pct as compared to 30 pct and 70 pct rolling reduction. In recrystallized regions, a significant proportion of coincidence site lattice (CSL) boundaries (Ʃ≤29) were observed regardless of the rolling reductions. Interestingly, a higher proportion of CSL boundaries (particularly Ʃ3 and Ʃ9) were observed amongst the grain boundaries between recrystallized grains of last and second last necklace layer (L-S); and grain boundaries between recrystallized grains of the last necklace layer (L-L). However, most of the grain boundaries between last necklace layer and the parent deformed matrix (L-D) have been observed to be random high angle grain boundaries (HAGBs). Generation of significant fraction of second order twin boundaries (Σ9) along with first order twin boundaries (Σ3) adjacent to the recrystallization front (i.e. behind the migratinggrain boundary) is a consequence of multiple twinning processes expected to occur during DRX. Here, role of Σ3 twin boundaries on the recrystallization process has been discussed. Grain boundary character evolution and its influence on DRX in the presently studied High-Entropy Alloy (HEA) has been inferred to be similar to previously reported observations on conventional low stacking fault energy materials.