Microstructure Characteristic and Mechanical Properties of a Novel Fe-0.15C-3.5Mn-1Ni TRIP Steel

Microstructure characteristic and mechanical properties after intercritical annealing (IA) of a novel Fe-0.15C-3.5Mn-1Ni steel were presented in this study. The results show that the IA parameter has a great influence on microstructure evolution of the steel. After IA treatment, the morphology consists of block-like retained austenite (RA) and ferrite, and the RA volume fraction increases gradually with the rising of annealing temperature and time. However, too high annealing temperature and time will reduce the stability of austenite instead, resulting in the segment martensite formation from metastable austenite during the IA treatment. Due to this martensite structure, the coarse austenite grain is divided into several fine and stable austenite grains, leading to the decline of the average RA grain size. Besides, the largest product of ultimate tensile strength and total elongation (UTS x TE) value of 35.1 GPa% can be achieved for the IA parameter of 675 degrees C for 2 h of the novel steel.