高铌TiAl/Ti600合金电子束焊接头组织与性能

Investigation on the microstructure and mechanical properties of high-Nb TiAl/Ti600 alloy electron beam welded joints

关键词:  Ti600合金  高铌TiAl合金  电子束焊接  显微组织  力学性能

Key words:  Ti600 alloy  high-Nb TiAl alloy  electron beam welding  microstructure  mechanical properties

摘要:

对高铌TiAl/Ti600合金进行了电子束焊接试验以便对高温钛合金与高铌TiAl合金高质焊接提供理论及试验依据，采用金相显微镜、扫描电子显微镜及X射线衍射仪等设备对焊接试样进行了分析.结果表明，高铌TiAl/Ti600接头极易产生裂纹缺陷.接头焊缝主要形成细针状α₂-Ti₃Al相及α-Ti相，而高铌TiAl侧热影响区呈现板条状及等轴组织形貌，Ti600侧热影响区为针状α'相.接头焊缝区硬度最大，达到586 HV，Ti600侧向高铌TiAl侧过渡过程中硬度逐渐增大，由焊缝到两侧热影响区硬度过渡梯度较大.高铌TiAl/Ti600电子束焊接头室温抗拉强度可达516 MPa，且接头断裂于偏高铌TiAl侧焊缝区，断裂性质为典型的脆性解理断裂，呈现穿晶断裂特征.

Abstract:

The electron-beam welding of high-Nb TiAl/Ti600 alloy was investigated in this paper to provide theoretical and experimental basis for the high-quality welding of high-Nb TiAl/Ti600. In this paper, optical microscopy, scanning electron microscopy and X-ray diffraction equipment are used to analyze the welding samples. The results showed that the joint was susceptible to solid-state cracking. Owing to fast cooling rate of electron beam welding, the acicular α₂-Ti₃Al phase and a little α-Ti phase were formed in the FZ (fusion zone), while the HAZ (heat affected zone) of high-Nb TiAl was composed of laths and equiaxial microstructure, and the acicular α'phase precipitated from the HAZ of Ti600 alloy. The joint exhibited a peak value in micro-hardness that occurred at the far end of FZ near the fusion line of high-Nb TiAl alloy and the hardness decreased from the weld seam to the both sides of base metals. The ultimate tensile stress of the as-welded specimen was 516 MPa, and the fracture occurred at the FZ on the side of TiAl alloy. It exhibited brittle cleavage fracture mode and also presented a characteristic of transgranular fracture.