The processes of microstructural evolution in titanium during deposition by cold spray were investigated. Titanium particles underwent plastic deformation at very high strain rates, resulting in (a) extensive refinement and (b) large inhomogeneities in microstructure. There were large nanostructured areas (several micrometres in extent) with high dislocation densities and subgrain sizes less than 100 nm. Dense dislocation tangles and elongated subgrains were observed in other places. It is hoped that by further understanding the microstructural changes that occur during cold spray, improvements in mechanical properties may be realised.

This study investigates microstructural alterations in copper powder during cold spraying. A highly nonhomogeneous structure was observed with average strains of almost 50% close to the interface. Large strains and high strain rates resulted in significant grain refinement and the formation of sub 100-nm grains. Deformation occurred by slip and twinning, the latter promoted by impurities in the copper feedstock. Thin foils from the deposits were studied by TEM analysis and cross-sections of deformed particles were made and examined using FIB-SEM techniques.