Ti/Al异种合金电弧熔钎焊接头界面断裂行为分析

采用TIG电弧的方法实现了钛合金与铝合金熔钎焊连接,分析了不同焊丝形成的熔钎焊接头的界面组织和断裂特征.结果表明,纯铝接头界面为单一的TiAl3相,裂纹主要沿着TiAl3反应层与焊缝之间的界面扩展.拉伸时首先从坡口拐角启裂,当裂纹扩展至接头反面时,断裂扩展形式转变为从焊缝金属撕裂,接头抗拉强度为139MPa.添加Al-Cu-La焊丝的接头界面结构为TiAl3+ Ti2Al20La双化合物层,拉伸时沿TiAl3反应层与钛合金界面开裂,以界面内的微裂纹为裂纹源并向反应层内扩展,属于准解理断裂,接头抗拉强度达270 MPa.稀土La元素作用下形成的双化合物层是提高接头强度的关键.

Analysis of interface fracture behavior of arc fusion-brazed joint between titanium and aluminum dissimilar alloys

Fusion-brazing of titanium alloy to aluminum alloy was achieved by TIG arc,and the interface microstructure and fracture characteristics of the joints made with different fillers were analyzed. The results indicate that the interface microstructure in the joints with pure Al filler consisted of TiAl₃ phase,and cracks initiated at the interface corner and propagated along the interface between TiAl₃ layer and welded seam. The facture style changed to tearing through the welded seam when the crack propagated to the back side,and the tensile strength of the joint was 139 MPa. In contrast,the interface of the joints with Al-Cu-La filler exhibited dual layers,containing TiAl₃ and Ti₂Al₂₀La phases. The fracture happened along the interface between TiAl₃ layer and Ti alloy substrate. The microcracks at the interface acted as the crack sources during the tensile test,and the fracture occurred in the interfacial layer with quasi-cleavage features. The tensile strength of joint with Al-Cu-La filler reached 270 MPa. The double compound layers formed due to the effect of La, which was the key to improve the joint strength.