Q. Tang; M. Hassani
Acta Materialia 302 (2025) 121655
While metallic particle size effects on impact-induced bonding behavior have been studied, the size effect on the properties that emerge at bonded interfaces remain elusive. In this study, we systematically study the effect of particle size on impact-induced bond strength using the Laser-Induced Projectile Impact Test (LIPIT) and subsequent in-situ microtensile measurement of interfacial strength at the micrometer scale. Our results show that bond strength at the impact center increases from 35±0.2 MPa to 45±0.7 MPa as particle size increases from 20±0.5 µm to 39±0.5 µm, at a fixed impact velocity of 860±12 m/s. A physically based finite element framework was developed to understand the mechanisms underlying this size effect. In contrast to the interface periphery, where the size effects are typically associated with elevated adiabatic heating, we found that increasing particle size does not significantly raise the local temperature at the impact center. Instead, the key effect is a substantial reduction in local strain rate—by nearly an order of magnitude as particle diameter increases from 10 µm to 50 µm. This slower strain rate sustains higher interfacial pressure for longer duration, facilitating stronger bonding through greater exposure of fresh metallic surface. It also promotes more distributed plastic deformation, enhancing energy dissipation and reducing elastic recovery-induced damage at already bonded interfaces. These mechanistic insights offer a new perspective on the particle size effect on impact-induced bonding, with a focus on micrometer-scale interfacial properties, and shall prove useful in the performance-oriented design of processes that rely on impact-induced bonding.