Ti/Al异种合金电弧熔钎焊接头温度场与界面微观组织

采用交流TIG焊电弧与AlSi12焊丝实现了TC4钛合金与LF6铝合金熔钎焊连接,通过有限元软件分析接头温度场,并利用扫描电镜观察接头钎焊界面的微观组织特征.结果表明,接头温度分布极不均匀,钛侧梯度大高温区窄,铝侧梯度小高温区范围广,冷却时高温区逐渐向钛侧偏移.当钨极正对钛钝边时,等温线平行于钎焊界面,温度分布均匀,有利于形成组织均匀的界面反应层.冷体熔钎焊加速了钎焊界面的冷却,降低了钛的溶解量,可抑制金属间化合物的生长.化合物层形貌由空冷时的锯齿状转变为胞状生长.

Investigation on temperature field and interfacial microstructure of Ti/Al arc welding-brazing joint

Dissimilar alloys of TC4 titanium alloy and LF6 aluminum alloy were butt joined successfully by TIG arc and AlSi12 filler metals.Temperature distribution and relationship were investigated by finite element method(FEM) numerical simulation and experimental validation.The microstructure of the interfacial layers was measured by scanning electron microscopy(SEM).The results indicate that the temperature distribution of Ti/Al arc welding-brazing joint is extremely asymmetrical,the titanium side exhibits high temperature gradient and narrow high-temperature zone,while the aluminum side exhibits low temperature gradient and wide high-temperature zone.The high-temperature zone trends to assemble near the titanium side in cooling stage.The interface roughly parallel to the isotherm of the temperature field as the electrode point at titanium root face.This leads to a symmetrical temperature distribution at brazing interface and seam near titanium side,which can improve interfacial reaction nonhomogeneity.It is the key factor to form brazing interface with symmetrical microstructure and welding-brazing joint with high performance.The water cooling technology can accelerate the cooling process,cutting down the dissolution of titanium and retard the growth of intermetallic compounds.The interfacial reaction layer morphology is cellular rather than serrated shape in air cooling condition.