Nanoparticle Reinforcement in Friction Stir Welding of Dissimilar Aerospace Alloys

In this study, dissimilar sheets, magnesium alloy AZ91 and aluminum alloy AA6061, were welded using friction stir welding (FSW) with the incorporation of titanium carbide (TiC) reinforcing powders into the weld joints. A novel groove design was presented to restrict nanoparticle segregation during the welding process. Microstructure examination and phase constitution of the interfacial zones showed that the base materials reaction was successfully obtained in the presence of the TiC reinforcing particles. Changes in heat input and stir action had the most significant effect on microstructure evolution, the distribution of nanoparticles, and intermetallic compound formation. Microstructure refinement, the presence of thin intermetallic compounds (IMCs), and homogenous nanoparticle distribution in the stir zone (SZ) were identified as the fundamental factors for the increased mechanical properties of the weld specimens, namely strength, toughness, and hardness profile.