Strength gradient in impact-induced metallic bonding
Qi Tang, David Veysset, H. Assadi, Yuji Ichikawa, Mostafa Hassani
Abstract
Solid-state bonding can form when metallic microparticles impact metallic substrates at supersonic velocities. While the conditions necessary for impact-induced metallic bonding are relatively well understood, the properties emerging at the bonded interfaces remain elusive. Here, we use in situ microparticle impact experiments followed by site-specific micromechanical measurements to study the interfacial strength across bonded interfaces. We reveal a gradient of bond strength starting with a weak bonding near the impact center, followed by a rapid twofold rise to a peak strength significantly higher than the yield strength of the bulk material, and eventually, a plateau covering a large portion of the interface towards the periphery. We show that the form of the native oxide at the bonded interface—whether layers, particles, or debris—dictates the level of bond strength. We formulate a predictive framework for impact-induced bond strength based on the evolution of the contact pressure and surface exposure. In situ measurements reveal a significant strength gradient at interfaces formed by the supersonic impact of metallic microparticles on metallic surfaces, featuring weak central bonding and a rapid rise to a peak exceeding bulk material strength.