A Novel Strategy to Additively Manufacture 7075 Aluminium Alloy With Selective Laser Melting

Selective laser melting (SLM) has been successful in fabricating advanced engineering parts with high geometrical complexities. However, some metals or alloys with high strength, low weldability, and large freezing range, such as 7075 aluminium alloy, have low AM processability and are hard to be directly SLM-fabricated. Here, we proposed a novel strategy, combining substrate modification and inoculation treatment, to fabricate a crack-free and dense high-strength 7075 alloy using SLM at a broad processing window. Inoculation of the 7075 alloy powder with 1 wt.% Ti submicron particles substantially refine the Al grains, effectively increasing the cracking resistance. Furthermore, the SLM substrate was modified, which allows integration of thermal insulation materials, such as vermiculite, to the substrate. As a result, the melt pool cooling rate and thermal gradient during solidification were significantly reduced. This directly led to a reduction in thermal stress within the melt pool. With combination of the substrate modification and Ti inoculation, crack-free, fine-equiaxed microstructure was obtained in the SLM-fabricated 7075 alloy that has the mechanical properties comparable to its wrought counterpart. This strategy can be implemented to SLM of other engineering alloys with low AM processability, providing a foundation for broadening industrial applications of SLM.