Microstructural and Interface properties of aluminium alloy coatings on alumina applied by friction surfacing

Two large groups of materials, namely metals and ceramics, are used in mass quantities in today’s industry because of their outstanding properties. To achieve higher product performance dissimilar materials need to be combined in assemblies, but their joining is challenging. Using friction surfacing technology Al2O3 ceramic substrates were coated with an aluminium alloy (AlMg4.5Mn0.7). Earlier research by the authors suggested that two major bonding mechanisms, namely mechanical interlocking and van der Waals forces, are responsible for the bonding strengths achieved between the coating and the substrate. Further SEM, STEM, HRTEM and EDX analyses at a sub nanometer resolution were conducted and are presented in this paper. These analytical methods revealed that the aluminium coating and the Al2O3 grains form a sharp
17 boundary without evidence of either a chemical reaction or diffusion at the interface and suggest that the main bonding mechanisms for the Al/Al2O3 system are van der Waals forces. In addition, mechanical interlocking may serve to hold in position the interface surfaces, to preserve their
20 close proximity, allowing the van der Waals forces to persist.