Effect of laser power on the microstructure and mechanical properties of laser-assisted cold sprayed 7075 aluminum alloy deposits

Abstract

7075 aluminum alloy deposits were fabricated using a solid-state additive manufacturing (AM) technology called laser-assisted cold spray (LACS). The effect of laser power on the microstructure evolution and mechanical property in the LACSed 7075 deposits was investigated. The microstructure of all deposits was analyzed by optical microscopy (OM), X-ray diffraction (XRD), and scanning electron microscopy (SEM) attached with energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) systems. Pull-off adhesion, microhardness, and tensile tests were performed to assess their mechanical behaviors. The deposits showed a virtually linear increase in thickness with increased laser power and a minimum porosity of about 0.2%. With the accelerated diffusion of solute elements in deposits, lamellar η phase – Mg(Zn, Cu, Al)2 and Al7Cu2Fe precipitated along grain boundaries at 2.6 kW eventually. Meanwhile, significant grain growth and recrystallization were initiated at the severely deformed prior-particle interfaces. All the LACSed deposits exhibited a noticeable increase in adhesion strength and a slight decrease in microhardness compared to the CSed one. The ultimate tensile strength (UTS) and elongation to fracture (EL) were improved by up to ∼46% and ∼35% in LACSed 7075 deposits. The relationship between mechanical properties and microstructure and the contribution of underlying strengthening mechanisms involved in the LACS process were then thoroughly discussed.