Creep mechanisms of U720Li disc superalloy at intermediate temperature
Creep mechanisms of U720Li disc superalloy at intermediate temperature
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DOI：
10.1016/j.msea.2011.03.034
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发表时间：
2011-06
期刊：
影响因子：
6.4
通讯作者：
Yong Yuan;Yuefeng Gu;C. Cui;T. Osada;T. Tetsui;T. Yokokawa;H. Harada
中科院分区：
文献类型：
--
作者：
Yong Yuan;Yuefeng Gu;C. Cui;T. Osada;T. Tetsui;T. Yokokawa;H. Harada
用透射电子显微镜研究了U720Li盘形高温合金在725℃/630℃蠕变试验前后的显微组织。蠕变组织的演化分为三个不同的阶段(I、II和III)，分别对应于逐渐增加的0.1%、5%和27%的应变。在第一阶段，位错通过Orowan环绕过二次γ‘。在第二阶段，部分位错开始剪切二次γ‘，留下层错(SF)，并在部分晶内形成微孪晶。在第三阶段，由于很大的应变和增加的有效应力，发生了晶界滑移。结果表明，U720Li在725℃/630℃/630℃的蠕变机制随应变逐渐增大而演化。位错滑移和攀移相结合的Orowan环过程和部分位错剪切析出物是主要的蠕变机制。结果表明，减小二次γ‘晶间间距、强化二次γ’和降低γ基体的层错能是改善其高温蠕变性能的有效途径。
The microstructures of U720Li disc superalloy have been investigated by transmission electron microscopy (TEM) before and after creep test at 725 °C/630 MPa. The evolution of the crept microstructures was marked as three different stages (I, II and III) corresponding to gradually increased strain 0.1%, 5% and 27%, respectively. At stage I, dislocations bypassed secondaryγ′ via Orowan loops. At stage II, partial dislocations started to shear secondaryγ′, leaving stacking fault (SF) behind and microtwins formed in part of grains. At stage III, grain boundary sliding occurred due to very large strain and increased effective stress. The results indicated that the creep mechanisms of U720Li at 725 °C/630 MPa evolved with gradually increased strain. Orowan looping process combining dislocation slip and climb and partial dislocations shearing precipitates were the main creep mechanisms. It is suggested that decreasing the interparticle spacing of secondaryγ′, strengthening secondaryγ′ and decreasing stacking fault energy (SFE) ofγmatrix may be effective methods to improve the creep property at relatively higher temperatures.