The critical factors governing mechanical properties in hot-rolled Fe-0.2C-11Mn-(0-6)Al TRIP steels and fracture behavior

In the present study, we fundamentally explore the reasons underlying mechanical property variation in hot-rolled 11Mn transformation-induced plasticity (TRIP) steels with varying Al-content. With increase in Al-content, the ultimate tensile strength (UTS) was decreased, while total elongation (TE) was increased. The variation in UTS was mainly associated with the fraction of constituent phases and stability of austenite, while the increase in total elongation (TE) with increase in Al-content was related to the increase in the fraction of ferrite. Moreover, the Al-free steel, quenched from intercritical region experienced brittle fracture. When the Al-content was increased to 2 wt%, the total elongation increased to ~22-32% and is also attributed to TRIP effect. In 4Al steel, the tensile elongation was in the range of ~19-40%, and was associated with TRIP effect and cooperative dislocation slip. In 6Al steel, the cumulative contribution of transformation-induced plasticity (TRIP), twinning-induced plasticity (TWIP), and cooperative deformation of δ-ferrite led to high elongation of ~37-65%. The increase in the contribution of TRIP and TWIP with increase in Al-content led to dramatic change in the mode and characteristics of fracture.