显微组织与力学性能的影响
(1. 西北工业大学 材料科学与工程学院，西安 710072；
2. 北京钢铁研究总院，北京 100081)
摘 要: 研究等温和近等温锻造变形温度对电子束焊接的异种合金(Ti2AlNb金属间化合物与TC11两相钛合金)焊接界面的显微组织与接头拉伸性能的影响。采用OM、SEM对焊缝区组织及拉伸度样断口进行观察，并对接头的拉伸性能进行研究。结果表明：电子束焊接的Ti2AlNb/TC11异种合金焊接界面的显微组织和接头的拉伸性能对变形温度敏感，在950 ℃变形后，位于焊缝一侧的Ti2AlNb合金中O相的含量大大增加，而位于焊缝另一侧的TC11合金为等轴α相和条状α相的混合组织，但焊缝上仍可见到断续相连的晶界α/α2相；在1 010 ℃变形后，TC11合金具有魏氏体组织特征，这时焊缝上的晶界α/α2 相完全断开；经950 ℃变形的试样在室温拉伸时，在Ti2AlNb合金中发生脆性断裂，这与O相不易协调变形有关，经500 ℃高温拉伸时，合金表现出较高的强度和较好的塑性，这是由于焊接界面的α/α2相颗粒较小，断裂位置转移到TC11钛合金上所致；经1 010 ℃变形的试样表现出一定的强度，但是塑性严重下降，这与TC11钛合金的魏氏组织特征有关；因此，异种合金进行等温变形时，须严格控制变形温度。
关键字: Ti2AlNb合金；电子束焊接；界面；显微组织；力学性能
microstructure and mechanical properties of
electron beam welded joint of dissimilar titanium alloys
（1. College of Materials Science and Engineering, Northwestern Polytechnical University, Xi’an 710072, China;
2. Central Iron and Steel Research Institute, Beijing 100081, China）
Abstract:The effects of deformation temperature on the microstructure of welded interface and mechanical properties of joint by electron beam welded (EBW) dissimilar alloys were investigated. The microstructures of the weld and fractographs of samples were examined by OM and SEM. The results show that the microstructures of the welded interface are sensitive to the deformation temperature. After deformation at 950 ℃, the O phase content increases significantly in the Ti2AlNb alloy at one side of the weld, the microstructure consists of spherical and strip α phase in the TC11 alloy at the other side of the weld, but the grain boundaries α/α2 phase present discontinuously at the weld. After deformation at 1 010 ℃, the microstructure of the TC11 alloy shows Widmanstaten structure, however the grain boundaries α/α2 phases are cut completely. For the samples deformed at 950 ℃, during tensile tests at room-temperature, the brittle fracture takes place at Ti2AlNb alloy, which is related with the inhomogeneous deformation of the O phase. The higher strength and better ductility is because α/α2 phases are fine, the fracture transfers into TC11 titanium alloy in the tensile test at 500 ℃. For the samples deformed at 1 010 ℃, the ductility drop is related with Widmanstaten structure of TC11 alloy. The deformation temperature should be strictly controlled for the isothermal deformation of dissimilar materials joints.
Key words: Ti2AlNb alloy; electron beam welding (EBW); interface; microstructure; mechanical property
