(1. 中南大学 航空航天学院，长沙 410083；
2. 中南大学 材料科学与工程学院，长沙 410083；
3. 中南大学 粉末冶金国家重点实验室，长沙 410083)
摘 要: 采用机械球磨方法和放电等离子烧结(SPS)技术制备Ti-45Al-7Nb-0.3W(摩尔分数，%)合金。利用XRD、SEM及TEM等分析方法对球磨处理前后粉末的形貌、相组成以及SPS烧结体的显微组织结构进行观察和分析，并研究该球磨合金粉SPS烧结的致密化过程。结果表明：气雾化TiAl-Nb基合金粉末经球磨处理后，粉末产生大量变形、脆性断裂现象，粉末粒度明显减小；球磨处理使粉末中的β相消失、α相减少、γ相增多。TiAl-Nb基合金球磨粉在520 ℃就开始快速SPS致密化过程，在1000 ℃即可基本达到完全致密；而在500 ℃加热时，球磨粉烧结热膨胀现象消失，体积收缩明显，这主要与球磨处理后粉末内部大量缺陷引起的回复过程有关。TiAl-Nb基合金球磨粉SPS烧结体呈现由γ相和α2相构成的双相组织，并且随着烧结温度的提高，α2相含量有所增加；球磨处理后，粉末SPS烧结体中α2/γ片层结构的形成受到抑制。
关键字: γ-TiAl基合金球磨粉；放电等离子烧结；致密化；显微组织；相转变
（1. School of Aeronautics and Astronautics, Central South University, Changsha 410083, China;
2. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
3. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China）
Abstract:Ti-45Al-7Nb-0.3W alloy (mole fraction, %) was fabricated by mechanical milling and spark plasma sintering (SPS) technique. Using XRD, SEM, TEM methods, the morphology and phase constitution of alloy powders before and after milling as well as the microstructures of SPS sintered specimens were observed and analyzed. The densification course of the ball-milled alloy powders was also investigated. The results show that, after mechanical milling, serious plastic deformation and brittle fracture occur in the gas-atomized TiAl-Nb alloy powders, leading to the obvious decrease of its particle size. β phase in the microstructure of the powders disappears, the amount of α phases decreases and that of γ phases increases. For the ball-milled TiAl-Nb based alloy powders, the starting temperature of rapid SPS densification is 520 ℃, and a theoretical density can be obtained at the temperature of about 1000 ℃. When heated below 500 ℃，the sintering thermal expansion of the ball-milled powders disappears, and the shrink of the bulk becomes obviously, which are mainly related to the recovery process caused by lots of defects after ball-milling. The SPS sintered bulk of TiAl-Nb based alloy made of ball-milled powders shows a duplex microstructure composed of γ phase and α2 phase. The content of α2 phases increases with the sintering temperature increasing. After ball-milling process, the formation of α2/γ lamellar structure in the sintered body is inhibited.
Key words: γ-TiAl based ball-milled alloy powder; spark plasma sintering; densification; microstructure; phase transformation
