TC4－DT电子束焊接头显微组织及疲劳裂纹扩展行为

Microstructure and fatigue crack growth behavior of electron beam welded joints for TC4-DT titanium alloy

在光学显微镜下对TC4-DT钛合金电子束焊接头显微组织进行了分析,讨论了接头不同位置显微组织特征.比较了疲劳裂纹始于焊接接头不同位置时的宏观裂纹扩展路径及裂纹扩展速率,依据焊接接头显微组织特点讨论了显微组织对疲劳裂纹扩展行为的影响.结果表明,电子束焊接头沿熔深方向显微组织存在一定的差异;文中条件下,与母材区相比焊缝熔合区及热影响区具有较高的疲劳裂纹扩展抗力,导致裂纹扩展路径逐步偏向母材区,最后讨论了裂纹扩展路径的偏折对裂纹扩展速率的影响.

The microstructure of electron beam welded joints of TC4-DT titanium alloy was analyzed by optical microscope,and the microstructure characteristics of different position in the joint were also analyzed.The crack propagation path and its growth rate were investigated on the joint samples,which the initial crack appeared at different location of the welded joints.Based on the microstructure characteristics of the welded joints,the influences of the weld microstructure on fatigue crack growth behavior were discussed.The results show that there are differences in the microstructure for electron beam welded joint along penetration depth.The fatigue crack propagation resistances of the weld fusion zone and heat affected zone were higher than that of the base metal,and the crack propagation path of the joints gradually tended to base metal zone.The influence of the crack propagation path offsets on crack growth rate was finally discussed in the paper.