The relative contributions of TWIP and TRIP to strength in fine grained medium-Mn steels

A medium Mn steel of composition Fe-4.8Mn-2.8Al-1.5Si-0.51C (wt.%) was processed to obtain two different microstructures representing approaches in the hot rolling mill, resulting equiaxed vs. mixed and lamellar microstructures. Both were found exhibit a simultaneous Twinning Induced Plasticity Transformation (TWIP ? TRIP) mechanism where deformation twins ??-martensite formed independently twinning with strain. Interrupted tensile tests conducted order investigate differences structures between constitutive model used find that, surprisingly, contributed relatively little strength alloy, chiefly due fine initial slip lengths that then gave rise opportunity for work hardening by grain subdivision. Nevertheless, lower high-cost alloying additions than equivalent Dual Phase steels (2–3 wt% Mn) greater ductility, medium-Mn TWIP TRIP still represent an attractive area future development.