TiAl基合金电子束焊接头组织及转变规律

Microstructure and transformation of electron beam welded joints of TiAl base alloy

采用OM,XRD,SEM,TEM及EDS等测试方法分析了Ti-43Al-9V-0.3Y合金电子束焊接头各区域组织特征、相组成及其转变规律。结果表明,接头组织主要由B2相组成,还含有部分α2+γ双相片层组织及粒状γm相,稀土元素Y是以YAl2相形式存在并起到细化晶粒的作用。合金在热处理和电子束焊接时,液态金属在冷却过程中由于冷却速度不同而发生不同的转变:较低冷却速度时形成片层状组织和魏氏组织;冷却速度较快时易形成粒状γm相;冷却速度极快时只发生有序化转变。最终得到性能上存在差异的不同铸造组织。

The microstructural characteristics,phase composition and transformation of the electron beam welded(EBW)joints of Ti-43Al-9V-0.3Y alloy were investigated by means of the optical microscopy,X-ray diffraction,scanning electron microscopy,transmission electron microscopy and energy disperse spectrum.The results showed that the joint microstructure is mainly composed of B2 phase.The partial α2+γ two-phase lamellar structure and granular γm phase are observed.The lanthanon Y exists as YAl2 phase and refined grains.During the heat treatment and EBW of this alloy,different transformation of the liquid metal will take place duo to the different cooling rate in the cooling period.The lamellar microstructure and Widmanstaten structure will form because of low cooling rate.The faster cooling rate can lead to the formation of the γm phase.The ordering transformation only happens at very fast cooling rate.The different casting structures with different properties are obtained finally.