A cold-sprayed aluminum coating was fabricated using a mixture of atomized and cryomilled powder as feed-stocks. The microstructure in the particles' interfacial region of the atomized/cryomilled particles was investigated by transmission electron microscopy. The tongue-shaped grains with very low dislocation density were observed. The formation of the tongue-shaped grains was attributed to recrystallization dominated by strain-induced boundary migration. The driving force for such migration was here an obvious difference in the substructures on opposite sides of the grain boundary. A large boundary misorientation makes strain-induced boundary migration more viable and facilitates the grain boundary bulging into adjacent region of high stored energy. This partial reaction was also attributed to adiabatic shear instability due to severe impact during cold spraying, and it might be helpful to form ductile bonding in coatings and composite bulk materials.

Recrystallization in the Particles Interfacial Region of the Cold-Sprayed Aluminum Coating: Strain-Induced Boundary Migration. Y.Y.Zhang, J.S.Zhang: Materials Letters, 2011, 65[12], 1856-8