Effect of laser remelting on printability, microstructure and mechanical performance of Al-Mg-Sc-Zr alloy produced by laser powder bed fusion

Laser powder bed fusion (LPBF) is an advanced metal additive manufacturing technology, extensively employed in the aerospace, automotive, biomedical and military sectors. Generally, laser remelting is employed to improve the relative density and surface quality of LPBF fabricated components. Whereas, studies focusing on the influence of remelting on densification, surface roughness, residual stress, crystallographic orientation, microstructure, and mechanical performance of LPBF fabricated Al-Mg-Sc-Zr alloy are still inadequate. The effects of repeated employment of melting on a deposited layer are also not well understood. To address these issues, this work systematically investigated the effects of remelting and layer thickness on the densification, surface roughness, residual stress, crystallographic orientation, microstructure and mechanical performance of LPBF fabricated Al-Mg-Sc-Zr alloy. The experiment results indicated that remelting improved the densification of the specimens, owing to the elimination of large size pores. Meanwhile, laser remelting could significantly improve surface quality compared with single melting condition. The microhardness exhibited remelting dependence, as well as elongation to fracture. In summary, these results provide a fundamentally novel insight into how an integration of layer thickness and remelting can assist in the fabrication of high-performance lightweight Al-MgSc-Zr alloy parts.