Manipulating the fine grain nucleation in Sc/Zr-modified Al alloys through a novel process strategy of laser powder bed fusion

Abstract

Fine equiaxed grain structure demonstrated promising opportunities for reducing the solidification cracking and mechanical property anisotropy issues of Sc/Zr-modified Al alloys fabricated by laser powder bed fusion (LPBF), provided by sufficient Al₃(Sc,Zr) primary particles existed in the melt pool. Herein, we report a novel LPBF processing strategy to manipulate the fine equiaxed grain nucleation in Al alloys with a reduced addition of Sc/Zr elements. By periodically alternating the input laser process parameters between layers, we found that the nucleation of Al₃(Sc,Zr) primary particles can be significantly promoted along the melt pool boundaries. The proposed process strategy was further verified in a hot tearing susceptible Al-Cu-Sc alloy, which successfully improved its LPBF processability and mechanical property isotropy. The present study provides valuable insights for future microstructure and mechanical property optimizations of high strength alloys fabricated via LPBF.