Effect of prior martensite formation on the bainite transformation kinetics in high-strength 3% Mn multiphase steel

Abstract The work presents results on the effect of prior martensite formation bainite transformation kinetics in a 3% medium-Mn multiphase steel. material was subjected to two isothermal holding temperatures: 400 °C (without martensite) and 350 (with martensite). According obtained dilatometric results, leads acceleration kinetics. starts finishes much faster, when present before holding. microstructural investigation steel after heat treatment carried out using light scanning electron microscopy. microstructures were composed fine bainitic laths with retained austenite small amount martensitic-austenitic islands at °C. At presence large tempered detected. is mixture coarse laths. increase lath thickness attributed coalescence process occurring lower temperature. differences hardness treatments relatively (~ 13 HV10).