Creep-Fatigue Damage of Heat-Resistant Alloys Caused by the Local Lattice Mismatch-Induced Acceleration of the Generation and Accumulation of Dislocations and Vacancies
Creep-Fatigue Damage of Heat-Resistant Alloys Caused by the Local Lattice Mismatch-Induced Acceleration of the Generation and Accumulation of Dislocations and Vacancies
复制标题
局部晶格失配加速位错和空位的产生和积累引起的耐热合金蠕变疲劳损伤
DOI：
10.1115/imece2021-68489
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Hideo Miura
中科院分区：
文献类型：
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作者：
Yifan Luo;Shogo Tezuka;Koki Nakayama;Ayumi Nakayama;Ken Suzuki;Hideo Miura
用修正的Arrhenius方程研究了高温蠕变-疲劳载荷下镍基高温合金晶界强度的退化机制，该方程解释了应力诱导加速位错和空位的局部生成和扩散。EBSD分析证实，位错和空位开始在晶界和析出物与晶间的界面附近产生和积累。在晶格常数相差较大的界面附近，晶相和晶粒之间的晶格常数相差较大，加速了晶界的生成和积累。在恶劣条件下测得的位错和空位扩散激活能远低于热力学稳定条件下测得的。证实了高温拉应力作用下晶界结晶度和强度退化的加速机制主要有两种：位错生成和扩散的加速以及组元原子从晶界向外扩散而加速空洞的积累。这些现象可以用修正的Arrhenius方程来解释，该方程中的有效激活能由外加的名义应力和各界面周围的局域内应力之和定量地改变。
Degradation mechanism of the strength of a grain boundary in Ni-base superalloy under creep-fatigue loading at elevated temperature was investigated by using the modified Arrhenius equation, which explained the stress-induced acceleration of the local generation and diffusion of dislocations and vacancies. EBSD analysis confirmed that dislocations and vacancies started to generate and accumulate around grain boundaries and the interface between precipitates and matrix in grains. The generation and accumulation were accelerated around the interfaces with large difference in the lattice constant between the nearby crystallographic phases and grains. The activation energies of the diffusion of dislocations and vacancies measured under the harsh condition was much lower than those measured under the thermodynamically stable conditions. It was confirmed that there are two main acceleration mechanisms of the degradation of the crystallinity and strength of grain boundaries under a tensile stress at elevated temperatures: the acceleration of the generation and diffusion of dislocations and the acceleration of accumulation of voids due to the outward diffusion of component atoms from the grain boundaries. These phenomena were explained by the modified Arrhenius equations in which the effective activation energies were changed by the summation of the applied nominal stress and the localized internal stress around various interfaces quantitatively.