Additively manufactured Al–Mg–Ca–Sc alloy with hierarchical microstructure: strong and ductile at room and elevated temperatures

An Al-Mg-Ca-Sc alloy with low hot cracking susceptibility was designed and fabricated by laser powder bed fusion technology. A hierarchical microstructure, i.e., solute Mg, dispersed nanoscale Al3(Sc, Zr) precipitates in the grains and a discontinuous network of Al4Ca eutectic phases along grain boundaries, was constructed. The mechanical properties of the additively manufactured (AMed) alloy showed superior strength and ductility. The strength-elongation product of the AMed alloy is over eight times higher than that of the cast alloy at both room and elevated temperatures. The alloy retains 66% of its ultimate strength due to the high thermal stability of the microstructure whereas only 31% was left for the AMed Scalmalloy, when the temperature increased from room temperature to 200 ℃. Ab initio calculations revealed a strong grain boundary segregation tendency for Ca, whereas the segregation tendency was weak for other elements, unraveling the origin of the hierarchical microstructure.