Interfacial structure and strength of Al‐25Si‐4Mg‐1Cu joint brazed with Zn interlayer

Abstract

A high‐quality joint of the parent metal Al‐25Si‐4Mg‐1Cu alloy (AlSi alloy) was brazed to itself using Zn layer as a filler material. The typical microstructure of AlSi/Zn/AlSi joint was Al‐Zn solid solution, primary Si phase and α‐Al phase. When brazing temperature was increased from 400 to 405°C, Zn began to melt and reacted with Al diffused from base material, then Si phase formed. While the increase in brazing temperature to 415°C caused the gradual buring of Zn from Al‐Zn solid solution, and α‐Al remained. Furthermore, the shear strength of the joint increased because of α‐Al phase and Si phase formation. In addition, with brazing time extending from 8 to 12 min, the amount of Al‐Zn solid solution decreased, while the amount of Si phase and α‐Al phase increased, thus the shear strength of the joint was improved. While the increase in holding time extending to 14 min caused many micro‐voids formed, and the shear strength of the joint was reduced. Finally, the shear strength of the joint brazed at 415°C for 12 min reached 65.6 MPa.