Microstructure evolution and mechanical properties of high-performance Al–Mn–Mg–Sc–Zr alloy fabricated by laser powder bed fusion

The influence of aging temperatures on the microstructure and mechanical properties of an Al–Mn–Mg– Sc–Zr alloy prepared by laser powder bed fusion (L-PBF) was systematically studied. The results show that the fabricated alloy was a dense and crack-free piece with a fine grain size of 3.51 μm and a yield strength of (547±3) MPa. When the alloy was subjected to aging at 300 °C, a large amount of highly coherent Al3Sc nanoparticles (2–3 nm) precipitated from the Al matrix. The aged sample exhibited a high yield strength of (616±4) MPa, which can be attributed to precipitation strengthening, solid solution strengthening, and grain boundary strengthening. When the alloy was aged at a temperature higher than 300 °C, part of the dissolved Mn and Zr precipitated in the form of Al6Mn and Al3(Sc,Zr). When the alloy was aged at 500 °C, the Al6Mn and Al3(Sc,Zr) precipitates grew to approximately 600 and 30 nm, respectively, in size. Consequently, the yield strength of the alloy decreased to (372±3) MPa.