Quantifying dislocation density in Al-Cu coatings produced by cold spray deposition

This paper quantifies the plastic deformation in terms of dislocation density for a series of cold sprayed Al-Cu coatings with copper contents from 2 mass% to 5 mass%. The success of the deposition and consolidation of the feedstock powders during the cold spray process rely on the occurrence of significant plastic deformation. Inert gas atomized Al-Cu alloy powders were sprayed onto substrates made of an Al-Cu-Mg-Mn alloy (AA2024) to produce dense coatings using a low pressure cold spray system with helium as the carrier gas. X-ray diffraction patterns were obtained from the Al-Cu feedstock powder material and the cold sprayed coatings using a monochromatic X-ray source, and the dislocation density was determined via an X-ray whole profile analysis. Increasing the Cu alloy content (from 2 mass% to 5 mass%) systematically increased the dislocation density in the Al-Cu coatings from (4.3 ± 0.5) × 10¹⁴ m⁻² to (7.5 ± 0.8) × 10¹⁴ m⁻². The dislocation densities in the feedstock powders ranging from (0.4 ± 0.1) × 10¹⁴ m⁻² to (1.8 ± 0.2) × 10¹⁴ m⁻² were all lower than the dislocation densities in the corresponding coatings. The increasing deformation level in the Al-Cu coatings with Cu additions were confirmed by the classic and modified Williamson-Hall analyses of X-ray diffraction data, and peak breadth measurements from neutron diffraction data. A high density of dislocations was also observed in these coatings via electron backscatter diffraction and transmission electron microscopy.