Abstract
Ultrastrong and ductile lightweight materials are urgently needed, given the pressing demand for a broad range of structural materials characterized by energy efficiency and emission reduction. A novel austenitic lightweight steel Fe–28Mn–11Al–1C–5Ni (wt. %) with ultra-high strength (ultimate tensile strength of 1.7 GPa) and ductility (total elongation of 15%) was fabricated by a simple thermomechanical method of cold rolling and subsequent annealing. The final microstructure consists of ultra-fine recrystallized austenite grains, submicron scale B2 particles located at austenite grain boundaries and unrecrystallized austenite regions assembled with finer nanoscale B2 precipitates. Such a microstructure is superior to previous reported microstructures contains two precipitates of B2 particles and κ-carbides in tensile properties, because it synergistically combines fine grain strengthening and B2 precipitation strengthening effects. In addition, the microstructure evolution during annealing and tensile process were systematically investigated to illustrate the transformation mechanism and deformation mechanism of B2 phase.
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