放电电压对Cu/Al管磁脉冲-半固态复合辅助钎焊质量的影响

针对Cu/Al管连接,提出磁脉冲-半固态复合辅助钎焊新工艺。基于LS-DYNA对钎焊过程进行多物理场仿真分析,研究不同电压下半固态钎料流变规律及管壁受力情况。采用Zn-15Al钎料进行钎焊试验,考察了接头的力学性能及显微组织。结果表明:当二次放电电压为7 k V时,钎料与母材实现了良好的冶金结合,接头铝侧区域形成α-Al和金属间化合物CuZn5,钎料层则出现α-Al、富锌相以及CuZn5,铜侧区域形成大约4μm的扩散层、锯齿状三元相Al4.2Cu3.2Zn0. 7以及α-Al和花状CuZn5。拉伸测试结果表明接头强度高于Al母材,磁脉冲-半固态复合辅助钎焊新工艺能实现Cu/Al管的有效连接。

Microstructure and properties of Cu/Al joints brazed with Zn-Al filler metals

The mechanical properties and microstructural distribution of the Cu/A1 brazing joints formed by torch-brazing with different Zn-A1 filler metals were investigated. The microstructure of the Zn-A1 alloys was studied by optical microscopy and scanning electron microscopy, and the phase constitution of the Cu/A1 joints was analyzed by energy dispersion spectrometry. The results show that the spreading area of the Zn-A1 filler metals on the Cu and A1 substrates increases as the A1 content increases. The mechanical results indicate that the shear strength reaches a peak value of 88 MPa when A1 and Cu are brazed with Zn-15AI filler metal. Microhardness levels from HV122 to HV515 were produced in the three brazing seam regions corresponding to various microstructure features. The Zn- and Al-rich phases exist in the middle brazing seam regions. However, two interface layers, CuZn3 and A12Cu are formed on the Cu side when the A1 content in the filler metals is 2% and more than 15%, respectively. The relationship between intermetallic compounds on Cu side and Zn-xA1 filler metals was investigated.

Microstructure and mechanical properties of Cu/Al joints brazed using(Cu,Ni,Zr,Er)-modified Al−Si filler alloys

To design a promising Al−Si filler alloy with a relatively low melting-point,good strength and plasticity for the Cu/Al joint,the Cu,Ni,Zr and Er elements were innovatively added to modify the traditional Al−Si eutectic filler.The microstructure and mechanical properties of filler alloys and Cu/Al joints were investigated.The result indicated that the Al−Si−Ni−Cu filler alloys mainly consisted of Al(s,s),Al_(2)(Cu,Ni)and Si(s,s).The Al−10Si−2Ni−6Cu filler alloy exhibited relatively low solidus(521℃)and liquidus(577℃)temperature,good tensile strength(305.8 MPa)and fracture elongation(8.5%).The corresponding Cu/Al joint brazed using Al−10Si−2Ni−6Cu filler was mainly composed of Al_(8)(Mn,Fe)_(2)Si,Al_(2)(Cu,Ni)3,Al(Cu,Ni),Al_(2)(Cu,Ni)and Al(s,s),yielding a shear strength of(90.3±10.7)MPa.The joint strength was further improved to(94.6±2.5)MPa when the joint was brazed using the Al−10Si−2Ni−6Cu−0.2Er−0.2Zr filler alloy.Consequently,the(Cu,Ni,Zr,Er)-modified Al−Si filler alloy was suitable for obtaining high-quality Cu/Al brazed joints.

Ag对铜铝激光熔钎搭接焊接头组织和性能的影响

针对新能源车用Cu/Al焊接端子的功能特点,以Ag为中间层开展铜铝激光熔钎搭接焊工艺研究。通过添加不同厚度的银镀层和银箔,分析接头抗拉强度、电阻率、显微形貌和组织成分变化。结果表明,Ag中间层添加有利于改善焊缝成型和焊接质量,接头抗拉强度和电阻率均随Ag中间层厚度的增加先减小后增大;在添加厚度为20μm银箔时,抗拉强度提高了近1/3,电阻率减小至8.6×10^(-8)/Ω·m。这主要与Ag有效抑制铜铝液相熔合、控制二元脆硬相生成有关。在铜侧边界形成"啮齿状"Al-Al2Cu-Ag2Al三元共晶相,熔化区以枝晶"-Al为主,界面层化合物种类少、分布均匀,内部拉应力产生的裂纹减小,有利于提高接头强度和降低电阻率。