Cold spray deposition of nanocrystalline aluminum alloys

Aluminum 5083 powder was mechanically milled under liquid nitrogen to achieve a nanocrystalline grain size in the range of 20 to 30 nm. The powder was subsequently sprayed using a nozzle designed with a validated numerical model for cold spray technology. The resulting coatings were evaluated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), micro- and nanoindentation. The TEM analysis shows that the nanocrystalline grain structure of the cryomilled feedstock powder was retained after the cold spray process. A significant increase in hardness from 104 to 261 +/- 8 (HV300g) was observed when comparing the nanocrystalline coating with cast, coldworked, Al 5083. The ability to use cold spray to produce nanocrystalline large deposits was also demonstrated in this work.