Tensile properties and high temperature creep behavior of microalloyed Ti-Ti3Al-Nb alloys by directional solidification
Tensile properties and high temperature creep behavior of microalloyed Ti-Ti3Al-Nb alloys by directional solidification
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DOI：
10.1016/j.msea.2010.03.096
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发表时间：
2010-06-25
期刊：
影响因子：
6.4
通讯作者：
Peng, Liangming
中科院分区：
文献类型：
--
作者：
Luan, Qingdong;Duan, Qiuqi;Peng, Liangming
研究了定向凝固微合金化Ti-Ti3Al-Nb合金的显微组织、拉伸性能和蠕变行为。实验结果表明，添加少量的铬和钼可显著提高三元合金的强度、塑性和蠕变抗力。随着600℃和650℃应力的增加，蠕变的应力指数从3.5-5.3(LSR区I区)向8.3-12.6(HSR区II区)的较高值变化，而在700℃时获得了5.3-6.0的单一应力指数。反之，蠕变的真实激活能为303-324kJ/mol，与钛在α(2)-Ti3Al(288-312kJ/mol)中的自扩散激活能相近。透射电子显微镜观察表明，板条中的普通位错控制了变形后的组织。然而，在长期蠕变过程中，合金的初始组织不稳定，在高应力和中等温度下发生动态再结晶。I区的蠕变变形是位错控制的，而II区的反常高应力指数与再结晶效应有关，导致初始组织的总晶粒度减小。断裂模式和总应变取决于成分、测试温度和应力水平。扩展第三阶段的加速应变速率是由于组织的不稳定性或空洞或微裂纹的形核、合并和合并所致。(C)2010爱思唯尔B.V.保留所有权利
The microstructures, tensile properties and creep behavior of the Cr- and Mo-microalloyed Ti-Ti3Al-Nb alloys processed by directional solidification were investigated. The experimental results indicated that the strength, ductility and creep resistance of ternary Ti-Al-Nb alloy were remarkably enhanced by additions of small amounts of Cr and Mo. The stress exponent for creep showed a transition and varied from a lower value of 3.5-5.3 (LSR-region I) to a higher value of 8.3-12.6 (HSR-region II) with increasing stress at 600 and 650 degrees C whereas a single stress exponent value of 5.3-6.0 was obtained at 700 degrees C. Conversely, the true activation energy for creep was calculated to be 303-324 kJ/mol and fell into or was quite close to that for the self-diffusion of Ti in alpha(2)-Ti3Al(288-312 kJ/mol). TEM examinations revealed that ordinary dislocations in the lath dominated the deformed microstructures. However, the initial microstructure o the alloys was unstable during long-term creep exposure and dynamic recrystallization occurred at high stress and moderately high temperature. The creep deformation in region I was dislocation-controlled whereas the abnormally high stress exponent in region II was associated with the effects of recrystallization resulting in a reduction in the overall grain size of the initial structure. The fracture modes and tota strain were dependent on the composition, test temperature, and stress level. The accelerating strait rate in the extended tertiary stage was attributed to the microstructural instabilities or the nucleation coalescence and merge of voids or microcracks. (C) 2010 Elsevier B.V. All rights reserved