An Al-Zn alloy with outstanding processability by laser powder bed fusion

Aluminum alloys—particularly Al-Zn alloys—are well known for their susceptibility to hot cracking during laser powder bed fusion (LPBF) processing. In this talk, we demonstrate that increasing the Zn content beyond previously explored limits can, contrary to expectations, result in a highly processable alloy. Specifically, the study focuses on the LPBF processing window of an Al-20Zn-0.1Cr (wt.%) alloy. We show that dense, crack-free, and isotropic polycrystalline microstructures can be achieved across a broad range of volumetric energy density (VED) conditions. The formation of these crack-free and isotropic microstructures is attributed to the pronounced segregation of Zn solutes and pure Zn particles at grain and cell boundaries, which effectively bridge Al dendrites during solidification. Additionally, the presence of Zn/Cr nanoparticles within grain interiors further contributes to grain boundary pinning. This pinning effect remains significant even under high VED conditions, as the residual Zn content—despite some evaporation during processing—still far exceeds its room-temperature solubility. Overall, this talk introduces new pathways for designing Al-Zn alloys with enhanced processability via LPBF.