Outstanding improvement in the CSL distribution in interstitial free (IF) steel via strain annealing route

Abstract

In the last two decades, grain boundary engineering (GBE) study has neglected the high stacking fault energy BCC materials. Researchers have tried many single or multi-step strain recrystallization routes for improving the grain boundary character distribution (GBCD) in BCC materials, but the results have not been satisfactory. So, in this study, a single-step low deformation (5%, 10%) strain annealing route is employed for obtaining optimized GBCD and triple junction distribution (TJD) in interstitial free steel. This low deformation (5%) and low temperature (923 K) short annealing (10 min) treatment led to the evolution of 48.2% of Σ3, 54.3% of low Σ CSL boundaries, and 31.1% of special triple junctions (J2 and J3 type) in the microstructure. To the best of the authors' knowledge, these are the highest values reported for BCC material in literature. A good correlation is found between {111}〈110〉, {111}〈112〉 gamma fiber texture components and low deviation Σ3 boundaries. Moreover, a thorough analysis of average grain size, residual strain, GBCD, TJD, and grain orientation spread indicates that the regeneration mechanism (due to strain-induced boundary migration (SIBM)) is responsible for establishing a GBE microstructure in the thermomechanically processed sample (5%, 923 K, 10 min). The present work also explains the role of abnormal grain growth (AGG) on the deterioration of GBCD and TJD in the highly deformed (10%) samples.