一种钎焊AZ91D镁合金的新型纳米SiC颗粒增强Mg-Al-Zn-Y复合钎料

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

摘要:

采用一种新型纳米SiC颗粒增强Mg-Al-Zn-Y复合钎料（记为SiC_np/Mg-Al-Zn-Y），在钎剂保护下对AZ91D镁合金进行炉中钎焊。结果表明，钎缝显微组织由Mg₁₇Al₁₂共晶组织基体和α-Mg固溶体组成。纳米SiC颗粒（SiC_np）作为异质形核位点细化了钎缝显微组织，显著提升了钎焊接头的抗剪切强度。SiC_np/Mg-Al-Zn-Y钎料钎焊接头抗剪切强度（68 MPa）比Mg-Al-Zn-Y钎料提高了62%。计算表明，晶界强化是钎焊接头强度提升最有效的强化机制，其对抗剪切强度的贡献为42.7%。钎焊接头断口呈现典型的脆性断裂特征，裂纹起源于α-Mg固溶体周围分布的Mg₁₇Al₁₂共晶组织。

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.