(1. 中南大學(xué) 材料科學(xué)與工程學(xué)院，長(zhǎng)沙 410083；
2. 中南大學(xué) 粉末冶金國(guó)家重點(diǎn)實(shí)驗(yàn)室，長(zhǎng)沙 410083；
3. 中南大學(xué) 有色金屬材料科學(xué)與工程教育部重點(diǎn)實(shí)驗(yàn)室，長(zhǎng)沙 410083)
摘 要: 采用Gleeble-1500熱模擬機(jī)在變形溫度為1 000~1 150 ℃、應(yīng)變速率為10−3~100 s−1的變形條件下，研究Ti-47Al-2Cr-0.2Mo(摩爾分?jǐn)?shù)，%)合金的熱變形行為。利用光學(xué)顯微鏡和掃描電子顯微鏡分析合金在不同變形條件下的組織演化規(guī)律。結(jié)果表明：流變應(yīng)力隨著應(yīng)變速率提高和變形溫度降低而增大；在變形過(guò)程中，流變應(yīng)力隨著變形量增大而增大，當(dāng)流變應(yīng)力達(dá)到峰值后趨于平穩(wěn)，表明合金在變形過(guò)程中發(fā)生了動(dòng)態(tài)再結(jié)晶；熱變形過(guò)程的流變應(yīng)力可采用雙曲正弦本構(gòu)關(guān)系來(lái)描述，平均激活能為337.75 kJ/mol；從合金的組織演化過(guò)程中可以看出，合金中不均勻的原始組織得到明顯均勻化，變形后的組織是由α2/γ層片晶團(tuán)和γ晶粒組成的雙態(tài)組織，在α2/γ層片晶團(tuán)和γ晶粒的晶界交界處發(fā)現(xiàn)分布均勻的B2相，并且隨著變形溫度升高B2相數(shù)量逐漸減少。
關(guān)鍵字: TiAl基合金；熱變形；流變應(yīng)力；動(dòng)態(tài)再結(jié)晶；激活能；B2相
high temperature
（1. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
2. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;
3. Key Laboratory of Nonferrous Metal Materials Science and Engineering, Ministry of Education,
Central South University, Changsha 410083, China）
Abstract:The hot deformation behaviors of the Ti-47Al-2Cr-0.2Mo (mole fraction, %) alloy were studied with a Gleeble-1500 machine at 1 000−1 150 ℃ with the strain rate of 10−3−100 s−1. The microstructural evolution of the alloy was investigated by optical microscopy and scanning electron microscopy. The results indicate that the flow stress of the alloy increases with increasing strain rate and decreasing deformation temperature. The flow stress increases with increasing strain until the stress reaches the peak value, then the flow stress remains constant, which indicates that dynamic recrystallization happens during deformation. The flow behaviors are described by the hyperbolic sine constitutive equation, and the activation energy calculated is 337.75 kJ/mol. The as-forged microstructure consists of refined α2/γ and γ grains, and the grains are much homogeneous than before. The B2 phase distributes uniformly at the grain boundary of α2/γ and γ grains. The B2 phase decreases with increasing deformation temperature.
Key words: TiAl based alloy; hot deformation; flow stress; dynamic recrystallization; activation energy; B2 phase
