(1. 長安大學(xué) 材料科學(xué)與工程學(xué)院，西安 710064；
2. Waikato Centre for Advanced Materials and Manufacturing, University of Waikato, Hamilton 3216, New Zealand)
摘 要: 針對鑄態(tài)亞穩(wěn)β型Ti-5553鈦合金，基于熱模擬試驗，研究了合金在高溫高應(yīng)變速率條件下的熱變形行為，并發(fā)現(xiàn)了一種全新的動態(tài)再結(jié)晶機制。結(jié)合多種材料表征技術(shù)，揭示了新動態(tài)再結(jié)晶機制的微觀組織演變機理，并分析了變形參數(shù)對再結(jié)晶行為的影響。結(jié)果表明：亞穩(wěn)β鈦合金在高溫高速率條件下的顯著動態(tài)軟化是動態(tài)再結(jié)晶和流變失穩(wěn)共同作用的結(jié)果，動態(tài)再結(jié)晶產(chǎn)生新晶粒的形核位置、尺寸和組織占比都對熱變形參數(shù)有較高的敏感性。本文發(fā)現(xiàn)和揭示的新動態(tài)再結(jié)晶機制是連續(xù)和不連續(xù)這兩種常見機制混合而成的耦合機制，既包含了引發(fā)不連續(xù)動態(tài)再結(jié)晶的晶界應(yīng)變集中效應(yīng)，又包括了連續(xù)動態(tài)再結(jié)晶的亞晶旋轉(zhuǎn)形核過程。
關(guān)鍵字: 亞穩(wěn)β鈦合金；熱變形；微觀組織演變；變形機制；動態(tài)再結(jié)晶
（1. School of Materials Science and Engineering, Chang’an University, Xi’an 710064, China;
2. Waikato Centre for Advanced Materials and Manufacturing, University of Waikato, Hamilton 3216, New Zealand）
Abstract:Based on thermal-mechanical simulation, the hot deformation behaviour of as-cast metastable β Ti-5553 titanium alloy under the conditions of high-temperature and high-strain-rate was investigated thoroughly. With the combination of various characterization approaches, the detailed microstructure evolution process of the novel dynamic recrystallization (DRX) mechanism and the effects of deformation parameters on DRX were revealed and analyzed. The results show that the flow softening of the alloy under the conditions of high-temperature and high-strain-rate are dominated by the synergy of dynamic recrystallization and deformation instability. The nucleation site, grain size and fraction of the recrystallized grain show great sensitivity to the deformation parameters. The disclosed DRX process is revealed to be controlled by the coupling mechanism of widely-accepted discontinuous (DDRX) and continuous (CDRX) mechanisms, containing strain localization induced nucleation and sub-grain rotation induced transformation.
Key words: metastable β titanium alloy; hot deformation; microstructural evolution; deformation mechanism; dynamic recrystallization
