In-situ studies of micron-scale impact: from rebound and bonding to erosion

When micron-sized metallic particles impact metallic substrates at low velocities they rebound. The particles adhesively bond to the substrate at higher impact velocities. With real-time observations, we have recently resolved the transition between the rebound regime and the bonding regime. The existence and nature of a second transition from the bonding regime to another have been matters of speculation in recent years. Here with in-situ impact experiments at the micron-scale, we record a departure from the bonding regime at high impact velocities. We observe significant material loss, and thus confirm erosion at high impact velocities as envisioned in the field. We report an upper bound to the range of velocities that leads to ideal impact-induced bonding. We discuss erosion mechanistically, and further develop a predictive framework for the erosion velocity that can guide design against erosion.