Characterization of deformation-induced martensite with various AGSs upon Charpy impact loading and correlation with transformation mechanisms

Deformation-induced martensitic transformation (DIMT) during quasi-static loading has drawn much attention in recent years since it is considered as one of the key strengthening mechanisms advanced high-strength steels (AHSS). However, systematic investigations on at high strain-rates are scarce due to difficulties experimental designs. In this contribution, interrupted Charpy tests were used study sequence DIMT under (~102–103 s?1). Austenitic 321 stainless steel samples with increasing austenite grain sizes (AGSs) designed demonstrate change ?'-martensite and its morphology. Quasi-in-situ electron backscattered diffraction (EBSD) selected transmission microscopy (TEM) experiments have revealed that, AGSs increases, nucleation sites from boundaries ultra-fine-grained (UFG) additional twin fine-grained (FG) samples, finally ?-martensite coarse-grained (CG) samples. Due spatial constraints imposed by different crystallographic boundaries, morphology transformed shifts blocky UFG film-like CG FG having a mixed It found that changed can be understood considering combined effect stacking fault energy twinning stress austenite.