Interfacial structure and properties of Cu/Al joints brazed with Zn-Al filler metals
- Laboratory of Materials Welding and Joining (LMWJ), School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)
Highlights: • The formation mechanism of Cu side interfacial compounds of Cu/Al joints with Zn-Al filler metals are revealed accurately. • The Cu side interfacial structure is uncertain and dependent on brazing parameters, especially cooling rate after brazing. • The close relation among composition, brazing parameters, interfacial structure and mechanical properties is discovered. - Abstract: Seeing that opinions vary, no unanimous conclusion has been drawn on Cu side interfacial structure and its relationship with the mechanical properties of Cu/Al joints brazed with Zn-Al filler metals, XRD, SEM and HAADF-STEM were used to accurately reveal the Cu side interfacial structure and the mechanism concerned. The relationship among the brazing process, interfacial structure and mechanical properties of the joints was systematically studied. The following phenomena and principles were newly found and clarified. The Cu side interfacial structure are uncertain and dependent on brazing parameters, especially cooling rate after brazing, in addition to the composition of Zn-Al filler metal. High cooling rate promotes the formation of CuZn and Al{sub 4.2}Cu{sub 3.2}Zn{sub 0.7} compounds, while slow cooling rate is beneficial for the formation of Cu-Al interfacial compounds at the Cu side interface. Increasing brazing temperature or lengthening holding time enhances the dissolution of base metals, which results in the increase of Al and Cu contents at the Cu side interface, thus promoting the formation of CuAl{sub 2} compound. Besides, increasing Al content in Zn-Al filler metal also promotes the formation of CuAl{sub 2} compound by directly increasing Al content at the Cu side interface. The significant differences in joint strength are caused by the differences of Cu side interfacial compounds essentially. When the thin CuZn and Al{sub 4.2}Cu{sub 3.2}Zn{sub 0.7} layers exist at the Cu side interface, the brazed joint possesses high shear strength. On the contrary, the formation of Cu-Al compound layers at the Cu side interface, especially CuAl{sub 2}, will severely degrade the joint strength.
- OSTI ID:
- 22804943
- Journal Information:
- Materials Characterization, Journal Name: Materials Characterization Vol. 138; ISSN 1044-5803; ISSN MACHEX
- Country of Publication:
- United States
- Language:
- English
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