Ti / Al TIG微熔钎焊界面行为及接头断裂行为

以TIG电弧为热源,AlSi5焊丝为填充材料,采用SEM、EDS、XRD对Ti-6Al-4V(TC4)钛合金和AlMg6铝合金异种材料TIG微熔钎焊的接头、温度场以及断裂行为进行了研究。试验表明:焊接接头铝母材侧具备TIG填丝熔化焊特征,Ti母材处为钎焊特征。峰值温度的升高能够增加界面层厚度,峰值温度升高,界面层组织趋于复杂。降低高温停留时间能够减小界面层厚度,但随着峰值温度增加,过快的冷却速度会产生较大的内应力,形成贯穿界面的裂纹。钛/铝TIG微熔钎焊的断裂,铝侧发生的断裂是韧性+脆性的混合型断裂,气孔及微裂纹为断裂起源。钛合金的母材过量溶解或者熔化,会导致气孔直径增加,应严格控制热输入量及钛母材的熔化。

Interface Characteristics and Facture Behavior of TIG Arc Welding-Brazed Ti/Al Dissimilar Alloys

With TIG arc as heat source and AlSi5 wire as filling mental, the dissimilar material joint fabricated by TIG arc welding-brazing process between Ti-6Al-4V (TC4) and AlMg6 was studied with SEM, EDS and XRD. The temperature field and fracture behavior of the joint was investigated. The results show that aluminum side of the weld joint reveals a typical property of wire fed TIG welding, while Ti side which is base metal shows a property of brazing welding. Thickness of the weld interface increases with higher peak temperature and the interface microstructure becomes more complicated. Reducing high-temperature residence time can cut down the thickness of the interface, but with the peak temperature increasing, big cooling speed produces high stress in the joint, thus forming cracks through the grain boundary. In Ti/Al brazing weld joint, cracks which grow from gas cavity and micro-cracks in Al side are a typical hybrid composed of ductile and brittle fracture. Besides, over melting and dissolving of the Ti base metal will enlarge the size of the gas cavity, so the quantity of the heat input and melting of the base metal must be strictly controlled.