Mechanical properties and deformation behavior have been studied in two hot-rolled 0.2C-1.5Al-8.5Mn-Fe (1.5Al steel) and 0.2C-3Al-8.5Mn-Fe (3Al steel) transformation induced plasticity (TRIP) steels, subjected to an optimized quenching and tempering (Q&T) treatment. The study indicated that 1.5Al steel was characterized by excellent combination of ultimate tensile strength (UTS) of 1373 MPa, tensile elongation (TE) of 31.8%, and UTS×TE of 43.6 GPa%, where the superior mechanical properties are mainly attributed to the discontinuous TRIP effect. In contrast, 3Al steel indicated lower UTS, but higher TE of 34.5%, which resulted from the discontinuous TRIP effect and the cooperative deformation of δ-ferrite. The discontinuous TRIP effect is a consequence of varying degree of stability of austenite, which results from different austenite grain size, non-uniform C-content and Mn-distribution in lath-like austenite and blocky austenite.

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In the present study, we fundamentally explore the reasons underlying differences in mechanical properties in hot-rolled 0.2C-1.6Al-6.1Mn-Fe TRIP steels subjected to different heat treatments. Comparing with austenite reverted transformation annealing (ART) process, quenching and tempering (Q&T) process was effective in obtain excellent mechanical properties.