Effect of La₂O₃ Nanoparticles on the Brazeability, Microstructure, and Mechanical Properties of Al-11Si-20Cu Alloy

The Al-11Si-20Cu brazing alloy and its ex situ composite with the content ranging from 0.01 to 0.05 wt.% of La₂O₃ are produced by electromagnetic induction-cum-casting route. The brazeability of the alloy and composite samples are tested using the spreading technique according to JIS Z-3197 standard. The mechanical properties such as filler microhardness, tensile shear strength, and elongation of the brazed joints are evaluated in the as-brazed condition. It is reported that incorporation of an optimal amount of 0.05 wt.% of hard La₂O₃ nanoparticles in the Al-Si-Cu matrix inhibits the growth of the large CuAl₂ intermetallic compounds (IMCs) and Si particles. As a consequence, the composite filler brazeability, microhardness, joint tensile shear strength, and elongation are improved significantly compared to those of monolithic Al-11Si-20Cu alloy.