Activated dynamic strain aging of a TRIP590 Steel at 300 °C and low strain rate and relationship to structure

Abstract

Transformation-induced plasticity (TRIP) steel was subjected to intercritical annealing and bainite partitioning to elucidate the impact on mechanical properties at temperatures in the range of −70°C to 300°C and strain rates of 10−3 to 10−1s−1 and the behavior related to structure. At temperatures in the range of −70°C to 150°C, both the yield strength and tensile strength increased with decrease in the deformation temperature at a constant strain rate. The elongation-to-failure was maximum at room temperature, while the product of strength and ductility was highest at the lowest temperature of −70°C at various strain rates. Unexpectedly, the serrated flow was observed for specimens tested at 300°C, which is attributed to dynamic strain aging (DSA), an effect that became more pronounced with decrease in strain rate. The nanosized precipitates facilitated increase in dislocation density during plastic deformation by restraining recovery and annihilation of dislocations, leading to increase in stress with increase in temperature, an effect that decreased with increase in strain rate because of adiabatic heating.