Formation of persistent dislocation loops by ultra-high strain-rate deformation during cold spraying

Pure copper was deformed at ultra-high strain-rates by the technique of cold spraying. It was found that after annealing the hardness of the samples does not fall as low as is known for heavily deformed copper at normal strain rates, e.g., cold rolling. The reason for this is the presence of defects that do not heal out after annealing at 600 °C. These defects were identified as dislocation loops of the extrinsic and intrinsic kind. Possible mechanisms for the formation of these loops are discussed.