(1. 中國(guó)科學(xué)技術(shù)大學(xué) 近代力學(xué)系 中國(guó)科學(xué)院力學(xué)行為和材料設(shè)計(jì)開(kāi)放實(shí)驗(yàn)室，合肥 230027；
2. 西北有色金屬研究院，西安 710016)
摘 要: 在應(yīng)變速率為0.001~1 270 s−1、溫度為298~1 023 K條件下對(duì)魏氏組織和雙態(tài)組織的TC21鈦合金進(jìn)行拉伸試驗(yàn)，利用SEM對(duì)拉伸試樣的斷口進(jìn)行觀察。結(jié)果表明：TC21鈦合金的拉伸力學(xué)行為存在顯著的溫度和應(yīng)變速率相關(guān)性；當(dāng)應(yīng)變速率為0.001和0.05 s−1的屈服應(yīng)力—溫度曲線存在轉(zhuǎn)折點(diǎn)，且轉(zhuǎn)折點(diǎn)溫度隨應(yīng)變速率的增大而升高；當(dāng)溫度低于轉(zhuǎn)折點(diǎn)溫度時(shí)，相同氧含量的TC21鈦合金和多晶純鈦的屈服應(yīng)力具有相似的溫度相關(guān)性；微觀組織影響屈服應(yīng)力的幅值和拉伸塑性的大小，但不影響屈服應(yīng)力的溫度相關(guān)性和應(yīng)變速率相關(guān)性；除魏氏組織在室溫0.001 s−1時(shí)為穿晶和沿晶混合斷裂外，其他工況下的魏氏組織和雙態(tài)組織均為穿晶韌性斷裂；TC21鈦合金在拉伸變形過(guò)程中未出現(xiàn)絕熱剪切帶和形變孿晶。
關(guān)鍵字: 鈦合金；TC21鈦合金；微觀組織；魏氏組織；雙態(tài)組織；動(dòng)態(tài)力學(xué)行為；應(yīng)變速率
at elevated temperatures
（1. Department of Modern Mechanics, CAS Key Laboratory of Mechanical Behavior and Design of Materials,
University of Science and Technology of China, Hefei 230027, China;
2. Northwest Institute for Nonferrous Metals, Xi’an 710016, China）
Abstract:Tensile tests were performed on TC21 titanium alloy with Widmanstatten microstructure (W) and bimodal microstructure (BM) at temperature ranging from 298 to 1 023 K and strain rate ranging from 0.001 to 1 270 s−1. The results show that the temperature and strain rate have significant effects on the tensile behavior of TC21. At low strain rates of 0.001 and 0.05 s−1, a discontinuity is found in the yield stress—temperature curve. Below discontinuity temperature, the temperature dependence of the yield stress of TC21 is similar to that of cp-Ti that has the same interstitial solute concentration of oxygen. The microstructure affects the magnitude of yield stress and tensile ductility, but not the strain rate sensitivity and temperature sensitivity of the yield stress. The samples with Widmanstatten microstructure show a mixed manner of transgranular fracture and intergranular fracture at room temperature and strain rate of 0.001 s-1, while under other conditions both microstructures show a manner of transgranular fracture. Neither adiabatic shear band nor deformation twinning is found in the tested samples.
Key words: TC21 titanium alloy; Widmanstatten microstructure; bimodal microstructure; microstructure; dynamic tensile behavior; strain rate
