Relationship Between Process Parameters and Defects in Laser Powder Bed Fusion Additive Manufacturing of Crack-Sensitive Al–Cu–Mg Alloy

Abstract

Laser powder bed fusion (L-PBF) is an innovative technique used to manufacture complex and customized parts. However, fabricating crack-sensitive Al–Cu–Mg alloy L-PBF parts with controlled defect levels remains challenging, as the effects of processing parameters on defect evolution are not well understood. In this study, we systematically investigated the influence of laser power, laser scanning speed, and hatching space on defect formation and evolution in L-PBF printed Al–4.1Cu–1.5Mg–0.6Mn alloy. Our findings indicate that laser power and scanning speed greatly impact the occurrence of lack-of-fusion porosity, hot cracks, and gas-induced pores. Initially, the relative density of L-PBF printed samples increases (from 97 to 99 pct) with increasing volumetric energy density (from 200 to 830 J/mm³), but then decreases with further increases in volumetric energy density (>830 J/mm³). The introduction of alloying elements Cu and Mg leads to increased laser reflectivity and heat dissipation, which in turn affects hot cracking susceptibility (HCS) and reduces the printability of Al–Cu–Mg alloy. This research provides a process map to guide the L-PBF manufacturing of crack-sensitive Al–Cu–Mg alloys.