A Novel Mg-Al-Zn-Y Composite Filler Metal Reinforced with Nano-SiC Particle for Brazing AZ91D Magnesium Alloy

Abstract:

A new Mg-Al-Zn-Y composite filler metal reinforced with nano-SiC particle (referred as SiC_np/Mg-Al-Zn-Y) was used to braze AZ91D magnesium alloy in furnace under the protection of flux. The results show that the microstructure of the brazing seam is composed of Mg₁₇Al₁₂ eutectic matrix and α-Mg solid solution. Nano-SiC particle (SiC_np), as a heterogeneous nucleation site, refines the microstructure of the brazing seam and significantly improves the shear strength of the brazed joint. The shear strength of brazed joint with SiC_np/Mg-Al-Zn-Y (68 MPa) is 62% higher than that with Mg-Al-Zn-Y. The calculation shows that grain boundary strengthening is the most effective strengthening mechanism for improving the strength of joints, and its contribution to the shear strength is 42.7%. The fracture of the joint shows typical brittle fracture characteristics, and the crack originates from the Mg₁₇Al₁₂ eutectic structure distributed around the α-Mg solid solution.