A Novel Fabrication Route of Bulk Metallic Glasses by Cold Spray Technology

Description

Bulk metallic glasses (BMG) are specially designed alloys that remain amorphous during casting. They exhibit unique combinations of properties, such as high strength combined with low elastic modulus, which are not achievable in conventional materials. They have been finding more application in industry in recent years. However, their sizes are limited due to the fast cooling required for the retention of the glassy state and this restricts their application in some areas. This project will use a cold-spray process, which is a relatively new coating technology, to deposit BMG with dimensions exceeding the maximum size attained with casting. During cold-spraying, solid BMG powder is accelerated towards the substrate by a supersonic jet of carrier gas. The cold-sprayed BMG layer contains pores and dense shear bands networks, which are both reported to enhance the toughness of cast BMG. Fabrication of BMG-matrix composites will also be done by co-spraying tungsten carbide powder or graphite flakes with BMG powder. The microstructure and mechanical properties of samples fabricated through this novel technology will be characterized, and correlations will be established. The deformation mechanism of the BMG powder during cold-spraying is hitherto not well understood and the researchers will attempt to establish the mechanism through careful microscopic investigation.