Shock consolidation of nanocrystalline 6061-T6 aluminum powders

Fully and partially nanocrystalline aluminum alloy powders made by cryomilling and plane-strain machining are dynamically consolidated into bulk compacts using a three-capsule gas-gun compaction geometry. Compacts with 98-99% theoretical mass density are produced, while retaining unique features of their initial microstructures. The microstructure of the fully nanocrystalline cryomilled powder compacts consists of 50-150 nm-thick elongated laths and 10-50 nm equiaxed grains. Partially nanocrystalline plane-strain machined powder compacts retain their bimodal microstructure composed of nanoscale grains near the particle surfaces and larger microscale grains with high dislocation densities in the particle interior. In this paper, the powder processing and compaction approach, and their effects on the physical, microstructural, and mechanical properties of the final compacts are described.