Novel medium-Mn (austenite + martensite) duplex hot-rolled steel achieving 1.6 GPa strength with 20 % ductility by Mn-segregation-induced TRIP mechanism

Ultra-high-strength (over 1 GPa) hot-rolled steel sheets have been actively developed to protect passengers in cases of vehicle crashes, and their applications have been expanded to cold-rolled steel sheets. A major alloying element for forming meta-stable austenite is Mn in (austenite + martensite) duplex microstructures, which is readily obtained at medium-Mn level ((3–10) wt.%). However, these medium-Mn hot-rolled duplex microstructures...