化学镀锡钎料钎焊黄铜的接头组织和力学性能

Effect of Brazing Alloys with Tin Electroless Plated on Microstructure and Mechanical Properties of Brass Brazed Joints

摘要:

采用化学镀方法在BAg45CuZn钎料表面镀覆微米锡层,并用镀锡银钎料以火焰钎焊工艺连接H62黄铜。借助金相显微镜、扫描电镜(SEM)和X射线衍射仪(XRD)分别分析锡化学镀层、H62黄铜钎焊接头的显微组织和物相,并利用万能拉伸机和SEM表征钎焊接头的抗拉强度和断口形貌。结果表明,锡化学镀层结晶晶粒呈现明显的(110)、(210)择优取向,化学镀锡银钎料连接的接头中母材与钎缝结合紧密,接头组织中富Cu相减少,出现Cu₅Zn₈化合物相。随着基体钎料表面镀锡含量升高,钎焊接头的抗拉强度呈现先升高后降低趋势。在化学镀锡含量为6.0 %时,钎焊接头的抗拉强度为353 MPa。镀锡前后钎焊接头的拉伸断口均呈现韧性断裂。

Abstract:

H62 brass joints were brazed successfully using BAg45CuZn brazing filler metals plated tin coatings. SEM and XRD were used to observe the surface microstructure and phase of tin coatings and H62 brass brazed joint. The tensile strength of H62 brass brazed joints were analyzed using tensile test machine. The results show that the crystallization orientation of tin coating displays (110) and (210) crystal faces. The interface brazing seam and H62 brass produce sound brazed joints after tin electroless plated on filler metal. Then Cu-rich phase in the microstructure of brazed joints decrease, but the Cu5Zn8 intermetallic compound generate. The tensile strength of brazed joints initially increase and then decrease with increasing of plating tin content. When the content of tin electroless plated coating is 6.0 %(wt.%), the maximum tensile strength of brass brazed joints is 353 MPa. The fracture morphology of brazed joints using filler metal with tin coatings display ductile fracture which the same with the joints using the BAg45CuZn brazing filler metal.