Effect of heat treatment on microstructure, hardness and corrosion resistance of 7075 Al alloys fabricated by SLM

The microstructure, hardness and corrosion properties of 7075 aluminum alloy fabricated by selective laser melting (SLM) under different heat treatment conditions were investigated The investigation results showed that the microstructure of the as-manufactured alloy fabricated by SLM has obvious inter-channel structure. When the solid solution plus single aging were used, the inter-channel structure of the alloys was beginning to fuse and disappear. The T phase could be dispersed in Al matrix, and a small amount of S phases and θ phases precipitated at the grain boundary. The hardness also increased compared with the as-manufactured alloy, and the average hardness is about HV123. When the solid solution plus double aging were used, the inter-channel structure of the alloy almost disappeared. The average of hardness is HV 158.The corrosion resistance (potential −0.805 V) of this alloy treated by solid solution plus double ageing also has an increase compared with the as-manufactured alloys (potential −0.87 V). S phases and θ phases precipitated at the grain boundary has a significant effect to improve the hardness and corrosion properties of Al alloys.