New insights into the cryogenic fracture mechanism of high-Mn austenitic steels using interrupted Charpy impact tests

Xia, B.*; Wang, H. H.*; Su, Y. H.  ; Xu, P. G.   ; Shinohara, Takenao   ; Wang, Y. W.*

The cryogenic fracture mechanism of high-Mn austenitic steels was investigated using a quasi-in situ experiment of interrupted Charpy impact test, together with electron backscatter diffraction and neutron Bragg-edge transmission imaging. The results show that voids coalesce through void sheeting at 77 K, a fracture mechanism associated with superior cryogenic toughness. The widely and ring-like distributed deformation twins ahead of the crack tip contribute limitedly to alleviating strain localization at 77 K. However, by suppressing the increase in stress triaxiality, deformation twins play a key role in promoting void sheeting and preventing the transition to quasi-cleavage fracture. This work lays the foundation for subsequent investigations into cryogenic toughening.