Cyclic deformation behavior of medium-manganese transformation-induced plasticity steel at elevated temperatures: Mechanical tests and microstructural characterization

Abstract

Medium-manganese transformation-induced plasticity (TRIP) steel, a new generation advanced high-strength steel, exhibits a combination of excellent strength and plasticity. Due to the TRIP effect, the cyclic deformation behavior and mechanisms of the steel are more complicated, especially at elevated temperatures. In this work, the monotonic and cyclic deformation of Fe-0.4C-7Mn-3.2Al steel were investigated at elevated temperatures, based on the previous experiments at room temperature. The influence of temperature on cyclic deformation characteristics and mechanisms were revealed by mechanical tests and multi-scale microstructural characterization. At 200 °C, the material exhibited cyclic stability under symmetric strain-controlled loading. Under asymmetric stress-controlled loading, it behaved steady ratchetting evolution under lower and medium stress amplitudes and significantly accelerated ratchetting evolution under higher stress amplitudes. The deformation mechanism at room temperature and 200 °C involved the coordination of dislocation slip and phase transformation. At 300 °C, the cyclic deformation characteristics of the material differed significantly from that at 200 °C. The cyclic hardening was observed under symmetric strain-controlled loading. Under asymmetric stress-controlled loading, the ratchetting strain rapidly got into shakedown after a few cycles under various stress amplitudes. The deformation mechanism at 300 °C was dominated by dislocation slip under dynamic strain aging.