The effect of alloying elements on cold spray challenges in 7075 aluminum alloys

High strength 7xxx series aluminum alloys are widely used in aerospace industry due to their specific strength. Repair and refurbishment are vital for structural components exposed to wear and corrosion, as replacing parts can be costly and time-consuming. Cold spray offers a suitable solution for repairing temperature-sensitive materials like aluminum alloys, owing to its low-temperature operation. However, there are challenges in cold spraying these 7xxx aluminum alloys, with nitrogen as the carrier gas, in terms of poor deposition efficiency and ductility. Even post-spray heat treatment has not been effective in obtaining acceptable ductility. The reason for this may be attributed to poor particle/particle bonding resulting from insufficient plastic deformation upon impact, and unfavorable particle surface/oxide characteristics. This study considers the role of each alloying element in alloy 7075 like zinc, magnesium, and copper, focusing on their contribution to the microstructure and oxide characteristics of the particles. By employing high-resolution electron microscopy to analyze the particle/particle interfaces in cold-sprayed coatings of 7075, a deeper understanding can be gained of how each of these alloying element might affect the interface through its impact on both the microstructure and oxide properties.