几种Ag基钎料钎焊NiTiNb形状记忆合金的接头组织及性能

采用AgCuInTi、AgCuTi和AgCuPd三种钎料对NiTiNb形状记忆合金进行真空钎焊,对应的钎焊温度分别为780℃、880℃和980℃,获得了冶金质量良好的接头。微观分析结果表明,三种接头的中心区域均生成了Ag基固溶体,在该固溶体区与NiTiNb母材之间生成了灰黑色扩散反应层,其中AgCuInTi和AgCuTi钎料对应接头的反应层中生成了(Cu,Ni)Ti化合物相,而AgCuPd钎料对应接头的反应层中生成了(Cu,Pd,Ni)-Ti相。测试三种钎料对应接头的室温抗拉强度,强度最高的是AgCuPd钎料对应接头,平均值达到593 MPa;其次为AgCuInTi钎料对应接头,抗拉强度为528 MPa;强度最低的是NiTiNb/AgCuTi/NiTiNb接头,平均值为459 MPa。保温时间对NiTiNb/AgCuInTi/NiTiNb接头微观组织及强度影响较小。分析接头断口发现,断裂主要发生在性能薄弱的(Cu,Ni)Ti相区或(Cu,Pd,Ni)-Ti相区。

Microstructures and properties of brazing joints in NiTiNb shape memory alloy with three Ag-based brazing filler metals

Vacuum brazing of NiTiNb shape memory alloy is studied with three kinds of AgCuInTi,AgCuTi and AgCuPd brazing filler metals respectively at 780 ℃,880 ℃ and 980 ℃,and good joints are achieved.The results show that a dark gray diffusion reaction layer is generated between base metal NiTiNb and Ag-based solid solution located in the central part of the brazing joints.(Cu,Ni) Ti compound phases are formed in the diffusion reaction layers of the joints brazing with AgCuInTi and AgCuTi,and (Cu,Pd,Ni)-Ti compound phases are formed in the diffusion reaction layer of joints brazing with NiTiNb/AgCuPd/NiTiNb.The average tensile strength of the joints brazing with AgCuPd is 593 MPa.The tensile strength of NiTiNb/AgCuInTi/NiTiNb and NiTiNbtAgCuTi/NiTiNb joints is 528 MPa and 459 MPa,respectively.The holding time has little effect on the microstructure and strength of NiTiNb/AgCuInTi/NiTiNb joints.The fractures of the three joints mainly occur in the (Cu,Ni) Ti phase or (Cu,Pd,Ni)-Ti phase,which have unsubstantial properties.