Response Characteristics and Adiabatic Heating during High Strain Rate for TRIP Steel and DP Steel

By using a static and high-speed material testing machine, tensile deformation behaviors of two kinds of Si-Mn TRIP (transformation induced plasticity) steels and DP (dual phase) steel were studied in a large range of strain rates (0. 001 - 2 000 s(-1)). Temperature variation during adiabatic heating and the amount of retained austenite at fracture were measured by an infrared thermometer and an X-ray stress analyser, respectively. The microstructure of steels was observed by optical microscopy (OM) and scanning electron microscopy (SEM) before and after tensile test. It was found. from the experimental results that the tensile strength of these steels increased, and the fracture elongation firstly decreased and subsequently increased, as the strain rate increased in the range of 0. 1 - 2 000 s(-1).The temperature raised during adiabatic heating of TRIP steel was in the range of 100-300 degrees C while that of the DP steel was in the range of 100-220 degrees C. The temperature rise of these steels increased with increasing the strain rate, as well as the amount of the transformed retained austenite in TRIP steels. It was confirmed that austenite to martensite transformation is not suppressed by adiabatic heating.