The Effect of Submicron Second-Phase Particles on the Rate of Grain Refinement in a Copper-Oxygen Alloy During Cold Spray

The effect of non-deformable submicron secondphase particles (d = 200-500 nm) on microstructural refinement during cold spray was examined. Using single particle impact testing, two types of splats were fabricated using two different feedstocks: a Cu-0.21wt.% O powder containing Cu2O second-phase particles and a single-phase Cu. Microstructural evolution analysis using high-resolution electron backscatter diffraction shows grain refinement occurred at a higher rate in the Cu-0.21wt.% O powder. That was due to dynamic recrystallization initiated by particle-stimulated nucleation (PSN). High-strain-rate deformation of cold spray was found to be the key to activate PSN. The present study suggests cold spray is a possible technique to fabricate ultrafine-grained materials by using feedstock containing second-phase particles.