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

Cold 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 degrees C for 75 min and heat-treated at 385 degrees 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 degrees 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 degrees C treatment. These results suggest Al F357 may be used in CS when appropriate powder heat treatments are applied.

Automated summary

The study found that heat treatment can induce microstructural modifications in both the powder and sprayed deposits, and X-ray diffraction showed the presence of eutectic Si, Mg2Si and SiO2 in all specimens. Spheroidization of Si significantly increased during heat treatment, with an increase in the fraction of Mg2Si during both treatments.