Towards understanding metallurgical defect formation of selective laser melted wrought aluminum alloys

The formation of balling, porosity and cracking defects is a vital obstacle in selective laser melting of wrought Al alloys. However, it lacks systematic research on the origins of these imperfections. Herein, the formation mechanisms and avoidance methods of metallurgical defects in slective laser melting (SLM)-processed Al–Cu–Mg alloy were investigated by numerical simulation and microstructure characterization. Process optimization by altering laser energy density can effectively suppress balling and porosity, thus enhancing relative density. Cracking results from the stress concentration and columnar grains arise due to the rapid cooling process during SLM. The methods that promote the columnar-to-equiaxed grain transition, such as microalloying by Sc/Zr/Ti elements, co-incorporation of ceramic particles and introducing ultrasound, can effectively enhance the cracking resistance and mechanical properties of wrought Al alloys.