(1. 中南大學(xué) 航空航天學(xué)院，長(zhǎng)沙 410083；
2. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長(zhǎng)沙 410083；
3. 中南大學(xué) 粉末冶金國(guó)家重點(diǎn)實(shí)驗(yàn)室，長(zhǎng)沙 410083)
摘 要: 采用機(jī)械球磨方法和放電等離子燒結(jié)(SPS)技術(shù)制備Ti-45Al-7Nb-0.3W(摩爾分?jǐn)?shù)，%)合金。利用XRD、SEM及TEM等分析方法對(duì)球磨處理前后粉末的形貌、相組成以及SPS燒結(jié)體的顯微組織結(jié)構(gòu)進(jìn)行觀察和分析，并研究該球磨合金粉SPS燒結(jié)的致密化過程。結(jié)果表明：氣霧化TiAl-Nb基合金粉末經(jīng)球磨處理后，粉末產(chǎn)生大量變形、脆性斷裂現(xiàn)象，粉末粒度明顯減小；球磨處理使粉末中的β相消失、α相減少、γ相增多。TiAl-Nb基合金球磨粉在520 ℃就開始快速SPS致密化過程，在1000 ℃即可基本達(dá)到完全致密；而在500 ℃加熱時(shí)，球磨粉燒結(jié)熱膨脹現(xiàn)象消失，體積收縮明顯，這主要與球磨處理后粉末內(nèi)部大量缺陷引起的回復(fù)過程有關(guān)。TiAl-Nb基合金球磨粉SPS燒結(jié)體呈現(xiàn)由γ相和α2相構(gòu)成的雙相組織，并且隨著燒結(jié)溫度的提高，α2相含量有所增加；球磨處理后，粉末SPS燒結(jié)體中α2/γ片層結(jié)構(gòu)的形成受到抑制。
關(guān)鍵字: γ-TiAl基合金球磨粉；放電等離子燒結(jié)；致密化；顯微組織；相轉(zhuǎn)變
（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
