A novel hierarchical manufacturing method of the selective laser melted Al 7075 alloy

Abstract

Manufacturing of the 7075 wrought aluminum alloys by selective laser melting technology (SLM) is extremely difficult owing to the inherent low laser absorptivity, poor weldability and cracking. To address these challenges and improve the mechanical properties of the SLM Al 7075 alloy, a novel hierarchical manufacturing method of the selective laser melted Al 7075 alloy from the nanometer scale to the millimeter scale was presented in this study. Nano-WC/Al 7075 sample with fine equiaxed grains was fabricated using SLM. Fewer cracks can be detected within the SLM nano-WC/Al 7075 alloy than the SLM Al 7075 alloy. A large quantity of nano-WC and sintered micro-WC particles were distributed within the equiaxed grains. A well-coherent interface with low lattice mismatch (i.e. 2.03%) is exhibited at the (111)α-Al/(001)WC planes. Al4W, Al2Cu and MgZn2 phases nucleated and grew on the surface of the nano-WC particles. A type of fine microstructure composed of the hierarchically reinforced micro/nano particles is produced in the SLM nano-WC/Al 7075 sample, resulting in an excellent micromechanical properties. Notably, wear rate of the SLM nano-WC/Al 7075 sample is about 40.4% lower than that of the SLM Al 7075 specimen, similarly with that of the SLM Ti6Al4V counterpart. These results highlight that the site-specific and quantitative modification of nano-WC particles of Al 7075 powder can be achieved using electrostatic self-assembly. Therefore, introducing nano-WC particles and generating multiple micro/nano reinforcement phases is an effective method to significantly improve their tribological properties.