Effect of Direct Aging on the Mechanical Properties of Heterostructured A20X Alloy Manufactured by Laser-Powder Bed Fusion

Abstract

Direct aging (DA), a post-heat treatment process that omits the solution treatment step, was applied to study its effects on the microstructure and mechanical properties of an A20X aluminum alloy fabricated by laser powder bed fusion (LPBF). The chemical heterogeneity in the as-built (AB) microstructure, characterized by Ti- and Cu-enriched cell boundaries, facilitates the rapid formation of nanosized precipitates during DA. Precipitation initiated at the cell boundaries and progressed into the matrix, with the size and density of Omega and theta ' phases increasing with aging time. DA slightly enhanced tensile strength compared to the AB condition; however, excessive aging time led to strength reduction owing to excessive precipitate coarsening along the cell boundaries. Additionally, aging mitigated dynamic strain aging, as evidenced by the reduced frequency of serrated flows that results in the ductility recovery in the full-aged sample. These findings emphasize the critical role of DA in tailoring the mechanical properties of LPBF A20X alloys, offering a simplified pathway for optimizing high-strength aluminum additive manufacturing components.