Mechanical properties and austenite stability in hot-rolled 0.2C-1.6/3.2Al-6Mn-Fe TRIP steel

In this investigation, the microstructures and mechanical properties of hot-rolled Fe-0.2C-6.1Mn-1.6Al (wt%) (1.6Al steel) and Fe-0.2C-5.9Mn-3.2Al (wt%) (3.2Al steel) transformation induced plasticity (TRIP) steels were studied. An optimized quenching and tempering (Q&T) adopted on 1.6Al steel led to ferrite-austenite microstructure characterized by 57% austenite and excellent combination of tensile strength of 1040 MPa and total elongation of 40.8% has been attained. The superior mechanical properties are mainly attributed to the discontinuous TRIP effect and the cooperative deformation of ferrite, where the discontinuous TRIP effect which is a consequence of the non-uniform distribution of manganese and carbon in austenite laths with various lengths. In contrast, 3.2Al steel with 34% austenite demonstrated lower tensile strength of 942 MPa and elongation of 35.4%, which is resulted from the TRIP effect and softening effect of ferrite.