Preparation of Aluminum Coatings Containing Homogenous Nanocrystalline Microstructures Using the Cold Spray Process

Abstract

Nanostructured materials are of widespread interest because of the unique properties they offer. Well-proven techniques, such as ball milling, exist for preparing powders with nanocrystalline microstructures. Nevertheless, consolidation of nanocrystalline powders is challenging and presents an obstacle to the use of nanocrystalline metals. This work demonstrates that nanocrystalline aluminum powders can be consolidated using the cold spray process. Furthermore, transmission electron microscopy (TEM) analysis of the nanocrystalline cold spray coatings reveals that the cold spray process can cause significant grain refinement. Inert gas atomized 6061 and 5083 aluminum powders were ball milled in liquid nitrogen resulting in micron-sized powder containing 250-400 nm grains. Cold spray coatings prepared using these feed stock materials exhibited homogenous microstructures with grain sizes of 30-50 nm. TEM images of the as-received powders, ball-milled powders, and cold spray coatings are shown.

Synthesis of nanodiamond-reinforced aluminum metal matrix composites using cold-spray deposition

“…Cold spray deposition further reduced the crystal size of all milled powders, in agreement with previous studies on aluminum [34]. Furthermore, for the same milling conditions, addition of ND led to a smaller overall crystal size as compared to pure Al.…”

Effects of Temperature of In-flight Particles on Bonding and Microstructure in Warm-Sprayed Titanium Deposits

“…In addition, the observation of interfacial microstructure of the sprayed particles and the substrate is meaningful to understand the adhesion of sprayed particles onto a substrate. Although several studies have been conducted on the microstructure of thick cold-sprayed materials (Ref [12][13][14][15][16][17], few investigations of sprayed single particles as well as splat/substrate interface region have been reported because such research inevitably requires transmission electron microscopy (TEM) and there used to be the difficulty in preparing a thin electron-transparent membrane out of such samples ( Ref 18). Recently, however, the focused ion beam (FIB) lift-out technique using micro sampling functions has enabled the preparation of high quality cross-sectional TEM samples ( Ref 19,20).…”

Advanced cold spray technology: Deposition characteristics and potential applications

“…The high grain boundary content of nanocrystalline materials results in grain boundary properties contributing significantly to the bulk material properties. Dislocation behavior in nanocrystals is different from larger crystals and can result in significant strengthening of the nanocrystalline metals [64], so cold-sprayed nanocrystalline materials will have broad applications.…”