铜夹层Ti-6Al-4V/AZ31B异种金属的扩散连接

Diffusion Bonding of Ti-6Al-4V Alloy and AZ31B Using Copper Interlayer

采用纯铜(Cu)箔作为中间过渡层在真空下对钛合金Ti-6Al-4V与镁合金AZ31B异种金属进行扩散连接。用冷场发射扫描电镜、能谱仪等对连接接头进行微观分析,利用拉伸试验获得接头强度。结果表明:530℃的扩散焊接头结合良好,界面区呈层状结构,相结构依次为γ-Cu固溶体、Cu3Ti、Cu2Al、Mg-Cu-Al三元金属间化合物、Mg17(Cu,Al)12及(α-Mg+Mg2Cu)共晶组织。520℃时,AZ31B/Cu界面无液相产生,无法实现AZ31B与Ti-6Al-4V的可靠连接;530℃时,共晶组织与金属间化合物共存于接头界面区,形成冶金连接;焊接温度为550℃时,共晶组织消失,接头界面区Mg-Cu-Al三元金属间化合物呈连续网状分布。焊接接头的剪切强度随保温时间的增加呈先上升再下降的趋势,30 min的接头剪切强度达到最大值,约为61 MPa。

The experimental investigation of diffusion bonding of titanium alloy （Ti-6A1-4V） to magnesium alloy （AZ31B） in vacuum was carried out by using pure copper as transition metal. The microstructure of the welded joints was studied by SEM, EDS, etc and the mechanical properties of the samples were tested by tensile experiments. The results show that： under the condition of 530℃ in holding time for 45 rain and pressure 2.5MPa, the microstructure at interface zone of diffusion brazing joint includes γ-Cu solid solution, Cu3Ti, Cu2A1, Mg-Cu-A1 ternary interrnetallic compounds, Mg17（Cu,A1）12 and （a-Mg＋Mg2Cu） eutectic structure. When the welding temperature is 520℃, there is no liquid in AZ31B/Cu interface zone, and it is unable to realize the connection of AZ31B and Ti-6A1-4V. At welding temperature of 530℃, the eutectic structure and intermetallic compounds are simultaneously distributed in the interface zone to form a metallurgical bond. As the welding temperature is 550℃, the eutectic structure disappears and the Mg-Cu-A1 ternary intermetallic compounds show a continuous network distribution. As the holding time increasing, the shear strength shows an increasing trend at first and then decreasing. When the welding process is 530℃ keeping for 30 min, the welding pressure is 2.5 MPa, the highest shearing strength of the welded joint can reach 61 MPa.