Effects of Strain Rate on Low‐Cycle Fatigue Behaviors of Fe–22Mn–0.6C TWIP Steel

The influence of strain rate on low‐cycle fatigue (LCF) behavior of Fe–22Mn–0.6C twinning‐induced plasticity (TWIP) steel is investigated by conducting LCF tests. The LCF tests are performed at a strain amplitude of 0–1.4% with strain rates of 8 × 10−4 s−1, 2 × 10−3 s−1, 8 × 10−3 s−1, and 2 × 10−2 s−1. The corresponding fatigue fracture morphologies and microstructure are also investigated. The results indicate that the TWIP steel shows initial cyclic hardening and cyclic saturation and then cyclic softening until final fracture at all strain rates. In addition, the fatigue life decreases with increasing strain rate due to enhanced dynamic strain aging (DSA). Moreover, the generation of persistent slip bands (PSBs) at high strain rates is also favorable for crack nucleation and fatigue crack growth, which is one of the primary reasons that lead to the premature failure of the fatigue specimens. At all given testing conditions, the fracture morphologies occur in a transgranular fracture mode. The effects of strain rate in the Fe–22Mn–0.6C TWIP steel on the cyclic stress–strain hysteresis loops, fatigue life, and microstructure evolution have been investigated. The fatigue life decreases with increasing strain rate due to the generation of dynamic strain aging (DSA) and persistent slip bands (PSBs).