TiNi/Nb/TC4真空电子束焊接接头裂纹

Cracks in TiNi/Nb/TC4 joints welded by vacuum electron beam welding

采用真空电子束焊接方法对3 mm厚TiNi合金与TC4异种金属进行对接焊,添加Nb为填充金属控制焊接裂纹的形成;分析了裂纹形成机理,Ti_2Ni脆性相的形成条件,接头元素分布特点及接头力学性能。结果表明:TiNi合金与TC4直接焊接易使焊接接头产生裂纹,大量Ti_2Ni脆性相的形成导致焊缝中裂纹和孔洞的产生,添加Nb为填充金属有效降低接头裂纹敏感性。填充金属厚度为0.55 mm时获得无裂纹缺陷的焊接接头,Ti_2Ni生成焓较小,使TC4侧熔合线附近形成Ti_2Ni脆性金属间化合物层,焊缝中心组织Nb含量较高,接头力学性能良好,抗拉强度达到391 MPa,伸长率为2.7%。

The TiNi alloys and TC4 alloys with thickness of 3 mm were welded by vacuum electron beam welding method,the formation of welding cracks was controlled by adding Nb for the filler metal.The formation mechanism of crack,the formation conditions of Ti2Ni brittle phase,the distribution characteristics of joint elements and the mechanical properties of joint were analyzed.The results show that it is easy to generate cracks in the joint when welding of TiNi alloy to TC4 directly;adding Nb as the filler metal can reduce the crack sensitivity of joint when welding TiNi alloy and TC4 alloy,the Ti2Ni brittle phase can contribute to the formation of cracks and holes in weld.The crack defect can eliminate when the thickness of the filler metal is 0.55 mm;the Ti2Ni brittle intermetallic compound layer formed near the fusion line of TC4 side due to the Ti2Ni enthalpy of formation is smaller;the Nb content in the center of weld is higher,the mechanical performance of joint is excellent.The tensile strength of joint reaches 391 MPa,and elongation is 2.7%.