Microstructure and Mechanical Property Evaluation of Aluminum F357 Powder for Cold Spray Applications

Abstract

AbstractCold spray (CS) is a solid-state additive manufacturing process that can create high-density, high-performance deposits for many applications. Aluminum alloys have been the target of recent CS research due to their excellent mechanical behavior when cold-sprayed. The introduction of new Al alloys to CS is of interest as unique properties may be achieved, especially when powder is heat-treated prior to deposition. In this study, three batches of Al F357 powder—a control as-atomized, heat-treated at 230 °C for 75 min and heat-treated at 385 °C for 6 h—were studied. Scanning electron microscopy revealed microstructural modifications after heat treatment in the powder and sprayed deposits. X-ray diffraction highlighted the presence of eutectic Si, Mg2Si and SiO2 in all specimens. Energy-dispersive spectroscopy showed the spheroidization of Si during the 385 °C heat treatment, with an increase in the fraction of Mg2Si during both treatments. Nanohardness and microhardness testing showed a decrease in hardness with thermal processing in both the powder and sprayed deposits. Tensile testing demonstrated ductile behavior from both heat-treated powders, but significantly higher strengths from the 230 °C treatment. These results suggest Al F357 may be used in CS when appropriate powder heat treatments are applied.