Composite fabrication in cast Al A206 via friction stir processing

Using friction stir processing (FSP) in forming localised or surface composites in castings can be very advantageous and has significant potential for many applications. Consequently, this study was initiated at ACRC to investigate the feasibility of fabricating composites in Al alloy castings via FSP. The study started with the Al A206 alloy matrix via an ex-situ technique, using a pre-machined groove with emplaced reinforcements. Three reinforcement materials (nanosized tantalum powders, nanosized SiC powders, and discontinuous reinforced aluminium) and several key processing parameters (number of FSP passes, the amount of the reinforced materials) were investigated and localised composites were produced successfully. This paper will present the experimental set-up, procedure, the microstructure and properties of the resulting composites, and a discussion of the formation mechanism of the composite and the influences of materials and process on the microstructure and properties.