Effect of grain size on impact and bonding behavior of metallic microparticles

• Single crystal (SC) and polycrystalline Al microparticles were impacted on SC Al. • SC Al rebounds faster than polycrystalline Al at a same impact speed. • SC and polycrystalline Al show similar critical bonding conditions. • Both bonded Al particles exhibit similar interfacial microstructure. Extrinsic parameters such as particle size influence the impact-induced bonding behavior of metallic microparticles, with larger particles generally exhibiting lower critical velocities than smaller ones. However, the impact of intrinsic parameters such as particle grain size on impact and bonding behavior for a given particle size remains unclear. In this work, we study this effect using laser-induced microparticle impact tests (LIPIT), where similar-sized Al particles with two distinct initial grain sizes—single-crystal (SC) and polycrystalline (∼4.5 µm grain size)—were impacted onto a SC Al substrate. The results indicate that, although rebound mechanics at low velocities are influenced by the initial grain size, the critical conditions for bonding remain largely unaffected. This finding is counterintuitive, as variations in the initial grain size would be expected to alter material strength and, consequently, the extent of plastic deformation in both the particle and substrate. Instead, we find that extensive impact-induced microstructural evolution near the interface dominates the response, erasing the differences between the two initial states at the critical bonding velocity. This finding is confirmed by Transmission Electron Microscopy (TEM) and Transmission Kikuchi Diffraction (TKD) studies, which reveal similar bonding quality and comparable microstructural evolution near the bonded interfaces.