Microstructure, metallurgical defects and hardness of Al-Cu-Mg-Li-Zr alloy additively manufactured by selective laser melting

Selective laser melting (SLM) is a promising technique for manufacturing 2xxx series Al-Cu alloy parts. However, the metallurgical defects in SLM severely limits their applications. In this work, SLM of a Li and Zr modified Al-Cu-Mg alloy (Al-4Cu-1Li-0.4Mg-0.5Zr) was studied with emphasis on its microstructure, metallurgical defects and hardness. The results show that microstructure is composed of fine equiaxed crystals (0.5-1 mu m) and columnar dendrites (10-12 mu m in length and 1-2 mu m in width) with pronounced pore and crack defects. The geometrically irregular micropores distribute at the boundaries of the molten pool while the regularly round micropores distribute randomly. Cracks were observed growing along the grain boundaries with high angle and almost parallel to building direction, which were mainly caused by local stress concentration in the liquid film. The texture of SLM-processed Al-Cu -Mg-Li-Zr alloy was found in {001}< 100 > and {001}< 310 > orientation. The microhardness improved as laser energy density increasing due to the higher cooling rate. This research provides useful guidance in the future for designing crack-free and high strength SLM printed 2xxx series Al alloys. (C) 2020 Elsevier B.V. All rights reserved.