Macro to nanoscale deformation of transformation-induced plasticity steels: Impact of aluminum on the microstructure and deformation behavior

This work aims to elucidate the impact of aluminum-content on microstructure and deformation mechanisms of transformation-induced plasticity (TRIP) steels through macroscale and nanoscale deformation experiments combined with post-mortem electron microscopy of the deformed region. The solid-state transformation-induced mechanical deformation varied with the Al contents, and influenced tensile strength-ductility combination. Steels with 2-4 wt% Al were characterized by TRIP effect. In contrast to 2Al-TRIP and 4Al-TRIP steels, twinning-induced plasticity (TWIP) was also observed in conjunction with strain-induced martensite in 6Al-TRIP steel. This behavior is attributed to the increase in stacking fault energy with the increase of Al content and stability of austenite, which depends on the local chemical variation. The study addresses the knowledge gap with regard to the effect of Al content on austenite stability in medium-Mn TRIP steels. This combination is expected to potentially enable cost-effective alloy design with high strength-high ductility condition.