Effects of Silicon on Microstructures and Properties of Al-40Zn-xSi Filler Metal

The effect of Si on the brazability and the microstructures of Al-40Zn-xSi filler metals were studied, and the microstructures and the mechanical properties of the joints brazed with Al-40Zn-xSi filler metals were investigated. The results indicate that the Al-40Zn-xSi filler metal presents the best wettability on 6061 aluminum alloy when Si content is and 4.0 wt%. The microstructure of the filler metal indicates that the primary silicon particles could be found when the silicon content exceeds 4.0 wt%. Al-Si eutectic mixed with Zn-Al eutectoid is located at α-Al interdendritic regions in the brazed seam after cooling with water. Moreover, the Al-40Zn-4Si joint possesses the optimum shear strength of 142.28 MPa. However, the excess of Si would increase the amount of brittle eutectic structure and primary silicon particles in the brazed joints, and thereby the mechanical properties will be deteriorated.