Synergistic coupling of Mn-doped skeleton and Mg-toughened matrix: towards a heat-resistant Al–La–Mg–Mn alloy

Abstract

Thermally stable three-dimensional (3D) skeleton coupled with the Mg-toughened matrix is employed to enhance the high-temperature strength in an Al–La–Mg–Mn alloy fabricated via laser powder bed fusion. The 3D skeleton exhibits a network and trans-granular structure with submicron cells, providing effective boundary strengthening to counter conventional grain boundary softening at elevated temperatures. Notably, Mn-doping introduces nanoscale Al6Mn precipitates into the skeleton, inducing additional microcracks that aid deformation coordination yet are buffered by the high-Mg toughened α-Al matrix during deformation. Quantitatively, the network structure contributes to over 30% and 40% yield strength increments at 200°C and 300°C, respectively. LPBF-fabricated Al–La–Mg–Mn alloy achieved outstanding high-temperature strength via boundary strengthening mechanism provide by the 3D skeleton.</p