Study on microstructure evolution and aging precipitation behavior of a novel Al-Li alloy fabricated by laser rapid melting.

For Sc-containing Al-Li alloys, Al 3 Sc precipitates exhibited inhomogeneous distribution due to limited solid solubility, segregation and sluggish diffusion of Sc. Laser rapid melting (LRM) with its merit of increasing the solubility of alloying elements during solidification represents a pivotal technique for exploring new alloy compositions. In this study, microstructure evolution and aging precipitation behavior of a novel Al-Li-Cu-Mg-Ag-Sc alloy fabricated by LRM were investigated during a systematically optimized T6 heat treatment. No primary Al 3 Sc particles were formed during the rapid solidification, but coherent Al 3 Sc nanoparticles were precipitated in the subsequent cooling process. Maximum hardness of 202 HV was achieved after aging at 175 °C/18 h due to combined precipitation strengthening of the Al 3 Sc, δ', Al 3 (Li, Sc) and T 1 phases. Coherent Al 3 Sc was concerned with a sequence of atomic displacement modulations that led to varying degrees of {002} Al planar collapse, while interfacial dislocations were emitted from the interface of Al 3 Sc with coherency lost. The existing Al 3 Sc phases were available to be acted as nucleation sites for δ′ and T 1 to form composite phases. These results can provide indispensable information for compositional design of novel Al-Li alloy specifically for laser additive manufacturing. • A novel Al-Cu-Li-Mg-Ag-Sc alloy was fabricated by laser rapid melting. • The maximum hardness achieved 202 HV for the peak-aged alloy. • The precipitates of peak-aged alloy were Al 3 Sc, δ', Al 3 (Li, Sc) and T 1 phases. • Al 3 Sc was formed by atomic displacement modulations inducing {002} Al plane collapse. • Al 3 Sc would act as the nucleation sites for δ′ and T 1 to form composites. [ABSTRACT FROM AUTHOR]