Microstructure And Properties Of 6061 And 7075 Aluminum Alloys Deposited By High-Pressure Cold Spray

High-pressure cold spray was used as a consolidation process for different aluminum alloy powders, including gas-atomized 6061 and 7075.  The relationship between the feedstock powders microstructure and the resulting local and coating-scale mechanical properties of the deposited materials was investigated. To characterize the microstructure, different microscopy techniques (TEM, SEM & EBSD) were utilized.  Aluminum powder particles experienced high deformation rates during impact, resulting in local microstructure variations, specifically grain size and dislocation density, between particle interfaces and interiors.  The effects of these microstructural variations on the quality of the deposition were also evaluated by nanohardness and mechanical testing. An increase in nanohardness was observed in particle interface regions. This increase in hardness was concluded to be the result of grain refinement promoted by local dynamic recrystallization, with limited influence of local dislocation density or associated strain-hardening behavior. The high-pressure cold spray process was found to produce very high strength coatings that even exhibit notable elongation at failure in tension.