Mechanical properties and microstructure of 3003 Al-alloy brazed joint with Zn-Al filler metal

3003 Al-alloy was brazed by Zn-Al filler metals with different Al contents.Mechanical properties and microstructure of the brazed joints were studied.The results indicated that the filler metal presented the best spreadability on 3003 Al-alloy substrate when the Al content was about 15%.However,the spread ability gradually deteriorated when Al content in Zn-Al filler metal exceeded 15%.The tensile strength of the brazed joint was measured and the brazed joint microstructures was observed by SEM,the results showed that by improving CsF-AlF3 flux,sound brazed joints could be obtained when Al content was lower than 15%,and three regions were found in the brazed joint interface:base metal,diffusion zone and interface zone.With the increase of Al content,the width of the diffusion zone increased.The results also showed that the tensile strength of the brazed joints was mainly affected by the shape and distribution of the massive microstructure in the brazing seam rather than the width of the diffusion zone.