Effect of strain rate on mechanical properties and microstructure of TRIP steel

Abstract

TRIP effect is one of the important features for TRIP steel. A Nb-Mo microalloyed TRIP steel was developed by employing two different soaking time during annealing, and tensile tests at three different strain rate for specimens after annealing were performed. The microstructures and the volume fraction of retained martensite were examined and analyzed. The result indicated that TRIP steel showed significantly different behaviour at different strain rates. The ultimate tensile strength and total elongation decreased with the strain rate increasing. The dynamic strain aging effect might occur at low strain rate. With shorter soaking time during annealing, microstructure with ultra-refined grain size could be achieved. Fracture surfaces were different at different strain rate. As strain rate increases, the fraction of retained austenite to martensite transformation at failure point decreases which leads to the difference of mechanical properties.