Constitutive modelling of the rate dependent flow stress of cast high-alloyed metastable austenitic TRIP/TWIP steel

The influence of strain rate and temperature on the resulting mechanical behaviour of a cast metastable austenitic CrMnNi-TRIP/TWIP steel was investigated. At ambient temperature and below, the formation of α′-martensite dominates causing a pronounced strain hardening. Various analytical models are available in literature and are mostly based on rule of mixture concepts (e.g. Ludwigson and Berger [22] and Narutani et al. [25]). These models were developed for commercial metastable alloys with medium stacking fault energy (SFE). However, for the herein-investigated alloy with very low SFE these models were found to be limited in describing the strain rate dependent material behaviour. A new model is presented predicting the flow stress of metastable alloys incorporating strain rate sensitivity, transformation strain, martensite kinetics and adiabatic heating.