In-situ Sip/A380 alloy nano/micro composite formation through cold spray additive manufacturing and subsequent hot rolling treatment: Microstructure and mechanical properties

Abstract

Cold gas dynamic spray (cold spraying, CS) has emerged as a promising solid state manufacturing technique to fabricate thick metallic deposits with limited risk of oxidation, phase transformations and residual thermal stresses. As-sprayed deposits usually exhibit poor mechanical properties and often require post-spray heat treatments to reduce inter-splat defects. In most of the cases, traditional heat treatments offer limited benefits to rejuvenate the mechanical properties of the deposit. This preliminary work presents an effective way to modify the microstructure and improve the mechanical properties of cold sprayed A380 aluminum alloy. As-sprayed alloy deposits were subjected to hot rolling treatments with different thickness reductions. Results suggest that the hot rolled samples show better strength and ductility compared with their as-sprayed state. Microstructural evolution and resulting mechanical properties, at different processing conditions, were analyzed through optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), high resolution transmission electron microscopy (HRTEM) and tensile tests. Sample with thickness reduction of 40% displayed highest values of ultimate strength (UTS, 420 ± 2.1 MPa) and elongation (Elf, 5 ± 2.3%) compared with the corresponding values of as-sprayed (100 ± 13.4 MPa, 0%) and conventionally heat treated (186 ± 17 MPa, 0.93 ± 0.05%) samples. The improvement in mechanical properties of the rolled samples were mainly attributed to the progressive elimination/reduction of inter-splat defects together with in-situ composite microstructure formation. EBSD and HRTEM revealed that in-situ composite structure was formed through progressive refinement and uniform distribution of Si particles in α-Al matrix containing coherent θ′ precipitates.