(1. 中南大学 粉末冶金国家重点实验室，长沙 410083；
2. 中南大学 材料科学与工程学院，长沙 410083)
摘 要: 采用光学显微镜、扫描电镜及透射电镜研究微量B和Y对铸造Ti-Al-Nb-W合金显微组织的影响。结果表明：Ti-47Al-4Nb-0.6W合金的基本凝固路线为L→β+L→(β+α)+L→(β+α)+γ→α+γ→(α+γL)+γ→(α2+γL)+γ，添加微量B和Y并未改变其基本凝固路径；微量B元素在合金中以短棒状TiB2相存在，细化了铸造Ti-47Al-4Nb-0.6W合金的晶团尺寸及片层间距；微量稀土Y元素主要以Y2O3氧化物颗粒的形式分布于片层晶团界面处，在B和Y的共同作用下，合金的片层晶团尺寸以及片层间距进一步减小。
关键字: TiAl基合金；显微组织；铸造合金；B；Y
（1. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;
2. School of Materials Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The effects of trace elements B and Y on the microstructures of cast Ti-Al-Nb-W alloy were investigated by optical microscopy, scanning microscopy and transmission electron microscopy. The results show that the following sequence of phase transformations takes place during the solidification of the Ti-47Al-4Nb-0.6W alloy as: L→β+L→(β+α)+L→(β+α)+γ→α+γ→(α+γL)+γ→(α2+γL)+γ. The solidification sequence remains unchanged after adding of trace elements B and Y. With the addition of a small amount of element B, the original colony and lamellar sizes of the Ti-47Al-4Nb-0.6W alloy are refined due to the formation of short-stick shaped TiB2 phases. The rare earth element Y is mainly distributed along the boundaries of the colonies in the form of Y2O3 particles. A further refined microstructure can be obtained as a result of the combined effects of elements B and Y.
Key words: TiAl based alloy; microstructure; as-cast alloy; B; Y
