Microstructure optimization of cold sprayed Ti-6Al-4V using post-process heat treatment for improved mechanical properties

Abstract

Cold spray is a solid state additive process involving layer-by-layer deposition onto a substrate at supersonic speed. In contrast with conventional additive manufacturing routes, particles remain at temperatures below the melting point. This feature would be beneficial for titanium alloys through limiting oxidation and epitaxial growth of β grains during manufacturing. However, low strength and ductility were reported for as-deposited materials. In this study, pathways were explored to improve the tensile properties of cold sprayed Ti-6Al-4V. Heat treatments of deposits were carried out using different temperatures and cooling rates. In addition, some samples were manufactured using in situ shot peening to reduce porosity. The resulting microstructures and mechanical properties were thoroughly characterized using different techniques. This approach allowed to reach comparable, or even higher, tensile strength and ductility than its conventionally processed counterparts in spite of residual porosity. Microstructural features were analyzed to clarify this behavior and the relationships between microstructure and tensile properties of cold sprayed Ti-6Al-4V deposits. The outcome of this study leads to promising insights into the use of cold spray as an alternative additive manufacturing route for Ti alloys.