Mechanical behaviors of a lower-Mn-added Fe–11Mn–10Al–1.25C lightweight steel with distinguished microstructural features.

Highlights • The austenite-based, duplex and triplex structures were developed. • Different types of intra-granular and grain boundaries κ -carbides were observed. • The microstructure-dependent mechanical responses were analyzed. • This work can be used to tailor phase constituents of medium-Mn lightweight steels. Abstract We elucidate three distinguished microstructural features and their contribution to the overall properties and strengthening in a Fe–11Mn–10Al–1.25C alloy treated at various temperatures. At 1000 °C, the nano-scaled ordered κ -carbides in the austenitic matrix contributed to YS (1041 MPa) without scarifying ductility (∼30%). At 900 °C, the significantly refined triplex microstructure with GB κ -carbides caused similar YS but limited ductility (∼8%). At 800 °C, a jump of YS but almost no ductility resulted from the synergic effects of the hard ferrite and lamellar microstructure. The microstructure-dependent mechanical responses were further clarified by analyses of flow curves and fractographs. [ABSTRACT FROM AUTHOR]