High-strain-rate behavior of metallic microparticles under laser-induced high-velocity impacts: the transition from rebound to bonding
Experimental investigations of elastic-plastic impact mechanics have largely been limited to either low velocities or large scales. However, impact behavior in the high-velocity and micro-scale regime is becoming increasingly relevant with the growing prominence of applications such as cold spray, erosion, and micrometeorite collisions. In cold spray, a metallic micro-particle impacting a metallic substrate with sufficiently high velocity will transition from rebound to bonding. This transition has been attributed to the emergence of jetting—the spall-induced ejection of material from the particle-substrate interface. Here, we present real-time observations of impacts in the high-velocity and micro-scale regime using an all-optical micro-ballistic test platform. We compare these experimental observations to plasticity-dominated impact models to develop a more thorough understanding of impact behavior in the transitional regime between plastic rebound and bonding. We first extract an effective dynamic yield strength for copper from experiments in which alumina spheres impact copper substrates. We then use this dynamic yield strength to analyze impacts of copper particles on copper substrates and find that, while plasticity is the dominant energy dissipation mechanism, jetting-associated mechanisms are increasingly important at higher impact velocities leading to bonding.