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The effect of strain rate on the work-hardening behavior of high-manganese twinning-induced plasticity (TWIP) steel has been investigated. The influence of adiabatic heating and deformation rate on the mechanical properties was studied by quasi-static and dynamic tensile tests with synchronous temperature and strain measurements. TWIP steel has excellent strain-hardening behavior under both quasi-static and dynamic loading conditions. Strain rate has negligible effects on yield and tensile strength, but the uniform and total elongation decreases under dynamic tests. TWIP steel has excellent energy absorption (EA) capacity of above 55 kJ/kg at all strain rates compared to dual-phase steels, transformation-induced plasticity steel and ferritic steels. However, the EA of TWIP steel is slightly lower compared to austenitic stainless steels. A rise in temperature due to adiabatic heating has led to the increase of stacking fault energy, thereby resulting in a change of twinning behavior or the promotion of dislocation glide under dynamic loading.

The strain hardening and damage behavior of Al-added twinning induced plasticity (TWIP) steels were investigated. The study was focused on comparing two different alloying concepts by varying C and Mn contents with stacking fault energy (SFE) values of 24 mJ/m 2 and 29 mJ/m 2 . The evolution of microstructure, deformation mechanisms and micro-cracks development with increasing deformation was analyzed. Al-addition has led to the decrease of C diffusivity and reduction in tendency for Mn-C short-range ordering resulting in the suppression of serrated flow caused due to dynamic strain aging (DSA) in an alloy with 0.3 wt.% C at room temperature and quasi-static testing, while DSA was delayed in an alloy with 0.6 wt.% C. However, an alloy with 0.6 wt.% C showing DSA effect exhibited enhanced strain hardening and ductility compared to an alloy with 0.3 wt.% C without DSA effect. Twinning was identified as the most predominant deformation mode in both the alloys, which occurred along with dislocation glide. Al-addition has increased SFE thereby delaying the nucleation of deformation twins and prolonged saturation of twinning, which resulted in micro-cracks initiation only just prior to necking or failure. The increased stress concentration caused by the interception of deformation twins or slip bands at grain boundaries (GB) has led to the development of micro-cracks mainly at GB and triple junctions. Deformation twins and slip bands played a vital role in assisting inter-granular crack initiation and propagation. Micro-cracks that developed at manganese sulfide and aluminum nitride inclusions showed no tendency for growth even after large deformation indicating the minimal detrimental effect on the tensile properties.

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