Precipitate response in GRCop-42 metallic microparticles under extreme impact conditions

GRCop-42 is a Cu-based alloy strengthened primarily through precipitation hardening by a single Cr₂Nb phase. While its deformation mechanisms under quasi-static conditions have been extensively studied, the behavior of these precipitates under extreme strain rates remains poorly understood. In this study, we investigate the high-rate response of GRCop-42 powder using laser-induced microparticle impact testing (LIPIT), where individual alloy particles are impacted onto a pure Cu substrate at velocities ranging from 100 to 600 m/s. We observe a transition from rebound to impact-induced bonding at ∼490 ± 11 m/s. Cross-sectional microstructural analysis of bonded particles reveals that, although high strain rate impact does not lead to significant precipitate fracture or coarsening, the precipitates undergo shape changes. At higher velocities, the Cr₂Nb precipitates exhibit increased aspect ratios, particularly near particle edges. This oblate deformation at the precipitate scale is attributed to localized temperature rise from adiabatic heating, driven by extreme plastic deformation. The effect is more pronounced at higher velocities and is spatially concentrated near the periphery of the particle–substrate interface.