Effect of deformation temperatures on microstructure and mechanical properties in a hot rolled Si-Mn TRIP steel

A hot rolled Si-Mn TRIP steel was subjected to different deformation temperatures in austenite non-recrystallization region during thermo-mechanical processes. The microstructural characteristics were analyzed, and its effects on mechanical properties were investigated. The results show that lower deformation temperature increases the contents of proeutectoid ferrite and retained austenite (RA) to 59.7% and 12.1% respectively, from lower levels. In the meanwhile, the product of ultimate tensile strength and total elongation is increased by 5 GPa·%. This is because higher fraction of RA particles with different size provide sustained transformation induced plasticity (TRIP) effect over a significantly wide strain range. The un-transformed RA in fractured tensile specimen has much smaller grain size with 0.12 μm in average diameter and higher carbon content of 1.54% in comparison to the case before fracture.