Alloy Design for Improved Precipitation Hardening in Additively Manufactured Al-Alloys

The powder bed fusion-laser beam (PBF-LB) process generates higher thermal gradients and solidification rates compared to conventional casting, leading to greater solute supersaturation and finer microstructures in Al-alloys, particularly for transition series elements. This enhanced supersaturation can be analyzed using the Scheil solidification model with solute trapping in Thermo-Calc software. This study examines the benefits of increased Zr supersaturation as an alloying element by comparing cast and additively manufactured (AM) samples, where AM samples exhibited a threefold increase in Zr solubility. This higher solubility enhances precipitation hardening, doubling the strengthening effect due to fine L1₂ Al₃Zr nanoprecipitates. The precipitation kinetics and resulting strengthening were accurately modeled using TC-PRISMA and validated against experimental results from Al-Mg-Zr and Al-Mn-Cr-Zr systems. These findings underscore the significance of rapid solidification in designing novel, precipitation-hardened Al-alloys.