On the stability, microstructure, and mechanical property of powder metallurgy Al-SiC nanocomposites during similar and dissimilar laser welding

Aluminum matrix nanocomposites consolidated by powder metallurgy (P/M) have significant potential for practical applications in the aerospace and automotive industries considering their admirable strength to weight ratio and good corrosion resistance. Due to dimensional restrictions in traditional P/M manufacturing routes, similar and dissimilar joining would be essential to design complex structures, however, the stability of Almatrix nanocomposites during joining process is a crucial issue. In this research, the stability of an Al-6 vol% (50 nm, ex situ) SiC-2 vol% (15 nm, in situ) Al2O3 hybrid P/M nanocomposite was evaluated during laser joining in comparison to similar and dissimilar joints with commercially pure aluminum (AA1050 alloy). The processing parameters were optimized with a constant focus spot size of 200 gm, laser power of 4 kW, and travel speed of 8 m/min to achieve fullpenetration joints. According to the experimental results, the similar P/M nano-composite exhibited unstable behavior during laser welding due to the formation of porosity associated with clustering and void expansion near SiC nanoparticles. Hence, the fusion zone in both joint designs consisting of similar and dissimilar containing nanocomposite material became heterogeneous due to the presence of clusters and shrinkage microvoids. The mechanical properties of weldments deteriorated considerably, with large fluctuations in the hardness profiles as well as low joining efficiency (< 30%) and brittle fracture. Defects present in dissimilar welds were mainly located at the nanocomposite side.