Ni-P镀层厚度对Cu/Al接头界面结构与力学性能的影响

Effect of Ni-P coating thickness on interfacial structure and mechanical properties of Cu/Al brazed joints

为了研究Ni-P镀层厚度对Cu/Al接头性能的影响,采用Zn98Al钎料对不同镀层厚度的T2紫铜与3003铝合金进行了钎焊,获得一系列钎焊接头,研究了钎料在镀层铜板上的铺展润湿性能,并采用光学显微镜、扫描电子显微镜对接头中Cu侧界面结构形态、化合物层厚度及种类等进行分析,进一步研究了镀层厚度对接头力学性能及断口形貌的影响。结果表明,随着镀层厚度增加,钎料在镀层铜板上的铺展面积呈先升后降的趋势,与无镀层铜板相比,当镀层厚度为5~20μm时,钎料的铺展面积由62.4 mm^(2)增加到189.5 mm^(2),增加了近3倍,此时,钎料的铺展面积稳定、润湿性能较好,有助于获得优质接头;与无镀层接头相比,镀层厚度小于5μm时,接头Cu侧界面结构仍为粗大的Cu_(3.2)Zn_(4.2)Al_(0.7)化合物层,接头强度变化不大;当镀层厚度为5~20μm时,镀层有效阻隔了Cu,Al原子扩散,接头Cu侧界面结构转变为Ni-P镀层+较薄的Al3Ni化合物层,同时接头抗剪强度也增加到最大值39 MPa,与无镀层接头相比提高了约21.8%;当镀层厚度大于20μm时,接头Cu侧界面结构转变为部分熔解的不规则Ni-P镀层+Al_(3)Ni化合物层,此时接头抗剪强度开始急剧下降。综合考虑钎料的铺展润湿性能、接头Cu侧界面结构及接头力学性能,确定Ni-P镀层最佳厚度为5~20μm。

To study influence of Ni-P coating thickness on mechanical properties of Cu/Al brazed joints,Zn98Al brazing filler metal was used to braze T2 copper with different coating thickness and 3003 aluminum alloy,and a series of brazed joints were obtained.Spreading wettability of brazing filler metal on coated copper plate was studied.Microstructure morphology of interface on Cu side,thickness and type of compound layer were analyzed by optical microscope and scanning electron microscope,and influence of coating thickness on mechanical properties and fracture morphology of brazed joints was further studied.The results showed that with the increase of coating thickness,spreading area of brazing filler metal on coated copper plate increased first and then decreased.Compared with uncoated copper plate,when coating thickness was 5~20μm,spreading area of brazing filler metal increased nearly 3 times from 62.4 mm^(2)to 189.5 mm^(2).In this case,spreading area of brazing filler metal was stable and wettability was better,which was conducive to obtaining well joints.Compared with uncoated brazed joints,when coating thickness was less than 5μm,structure at the Cu-side interface was still coarse Cu_(3.2)Zn_(4.2)Al_(0.7)compound layer,and shear strength of brazed joints had little change.When coating thickness was 5~20μm,the coating could effectively prevent diffusion of Cu and Al atoms,and structure at the Cu-side interface of brazed joints changed into Ni-P coating and thinner Al3Ni compound layer.Meanwhile,shear strength of brazed joints increased to the maximum 39 MPa,which was about 21.8%higher than that of uncoated brazed joints.When coating thickness was more than 20μm,structure at the Cu-side interface of brazed joints changed into irregular Ni-P and Al_(3)Ni compound layer,and shear strength of brazed joints began to decrease sharply.Considering spreading wettability of brazing filler metal,structure at the Cu-side interface of brazed joints and mechanical properties of brazed joints,the optimum thickness of Ni-P coating was determined to be 5~20μm.