Spreadability of Zn-Al filler metal and fracture mechanism of 6063 Al-alloy brazed joint

The spreadability of Zn-Al filler metal on 6063 Al-alloy surface were investigated, moreover, the strength and microstructure of 6063 Al-alloy lap-joints were studied. The results indicated that spreadability was improved with the increase of Al content in filler metal. When Al content was 22%, the filler metal got the best spreadability on 6063 Al-alloy surface. However, the spreadability decreased when Al content exceeded 22%. Furthermore, the brazed lap-joint mechanical property test results indicated that the strength of 6063 Al-alloy lap-joint was enhanced with the increase of Al content in filler metal. The highest strength of brazed joint was obtained when Al content is 22%, however, when Al content exceeded 22%, the dentritic eutectoid structure became larger in the brazing joint. Stress concentration emerged easily between large dendritic eutectoid structure and the surrounding structure. And the strength of brazed joint decreased gradually. The optimum fill metal possessing best comprehensive properties is 78Zn-22Al filler metal.