Enhanced ductility and strength of Al3Ti particles modified AA2024 alloys produced by laser powder bed fusion

Abstract

Particle-reinforced Al alloys prepared by laser powder bed fusion (LPBF) have excellent mechanical properties and thermal stability. Due to the similar crystal structure and excellent nucleation ability with Al, L1₂-Al₃Ti particle is chosen for the nucleant for Al instead of D0₂₂-Al₃Ti. In this paper, we obtained an L1₂-Al₃Ti particle-reinforced Al alloy by adding D0₂₂-Al₃Ti. The microstructure of the alloy was significantly refined, and its printability was notably improved. Specifically, the resulting microstructure consisted of fine equiaxed grains with an average size of 1 μm, attributed to the formation of L1₂-Al₃Ti particles. These particles act as effective heterogeneous nucleation sites for the α-Al matrix, facilitating heterogeneous nucleation and promoting grain refinement. The elimination of columnar grains and suppression of cracks resulted in the 3.2%Al₃Ti-modified as-printed sample exhibiting excellent mechanical properties, with an ultimate tensile strength of 425 MPa and an elongation of 13.9 %. After T6 heat treatment, the mechanical performance was further enhanced due to the combined effects of residual stresses elimination and aging strengthening, achieving an ultimate tensile strength of 533 MPa and an elongation of 14.8 %. This new intermetallic reinforced Al alloy provides new ideas and insights for obtaining strength-toughness synergy between Al alloys and their composites.