Characterization of mechanical behaviour of aluminum powders under fast dynamic conditions

Cold spray is a process belonging to the thermal spray family, characterized by relatively low temperatures and high particle velocities. Upon impact, particles undergo large plastic deformation at solid state in dynamic regime up to 10⁹ s^-1. The knowledge of powder behaviour in such conditions is essential to catch key phenomena in cold spray and a necessary step for a correct process modelling. However, little is known on mechanical behaviour of feed-stock powders when submitted to cold spray conditions. In this study, an approach focused on single particles combining laser shock induced impact, namely LASHPOL (LAser SHock POwder Launcher), and quasi-static compression was therefore developed. This method was applied in this study on spherical Aluminium powders but can work with any other powder material. The mechanical behaviour of powders was characterized and used to fit the parameters of Johnson-Cook constitutive model, by means of finite element inverse method. The combination of static and dynamic tests resulted in an original characterization of powder, which revealed having a different mechanical behaviour than the corresponding bulk material.