Strain rate-dependent plastic behavior of TWIP steel investigated by crystal plasticity model

A strain rate-dependent crystal plasticity finite element (CPFE) model was developed to describe the plastic behavior of TWIP steel over a wide range of strain rates, encompassing quasi-static to dynamic loadings. The developed model captures the effect of strain rate on the mechanisms governing dislocation motion and temperature rise. The mechanical behavior and underlying micro-mechanisms of TWIP steel during compression at different strain rates were then systematically investigated by combining the CPFE model with experimental tests. The results demonstrate that the developed model can accurately predict the mechanical response of TWIP steel over a wide range of strain rates from 10⁻³ s⁻¹ to 10⁴ s⁻¹. It was observed that the yield stress presents a gradual increase with increasing strain rates below a threshold value of applied strain rate, beyond which the yield stress increases sharply. The stress drop after yielding under high strain rates is found to be attributed to the decreased viscous drag stress by increased dislocation density. Further quantitative analysis results show that the contribution of deformation twinning to the macroscopic flow stress is negligible for both high and low strain rates, and the strain hardening behavior of TWIP steel is mainly dominated by the forest dislocation stress.