Selection of crack initiation locations of high cycle fatigue in high-Mn austenitic steel at 77 K

•Triple junction of grain boundaries is the preferential location for fatigue crack initiation.•Crack may initiate at twin boundaries under the shear stress.•Crack initiation of twin boundaries may be slowed down by stress relaxation caused by detwinning. In the present paper, a high-Mn austenitic steel with grain sizes of ∼27 μm was prepared to investigate the different Interactions between individual grain boundaries (IGBs), triple junctions of GBs (TJGBs), and Twin boundaries (TBs) with persistent slip bands (PSBs) at 77 K. TJGBs are the preferential locations for the fatigue crack initiation rather than IGBs and TBs. TBs have the best fatigue cracking resistance, when the PSBs on both sides of TBs are coplanar with TBs, Crack may initiate under the shear stress, but the shear stress acting on the crack propagation direction will be small, making TBs crack difficult to propagate. This process may be slowed down by stress relaxation caused by detwinning.