文献类型：期刊文献

英文题名：High- and Very High-Cycle Fatigue Behaviors and Crack Initiation Mechanism of Alloy 718 at 650°C

作者：Wang, Yong-Jie[1];Hu, Hua-Yan[1,2];Min, Lin[1];Zhao, Tian-Ji[2];Wen, Jian-Feng[1,3];Song, Miao[2];Tu, Shan-Tung[1,3]

机构：[1]East China Univ Sci & Technol, Sch Mech & Power Engn, Key Lab Pressure Syst & Safety, Minist Educ, Shanghai, Peoples R China;[2]Shanghai Jiao Tong Univ, Sch Nucl Sci & Engn, Shanghai, Peoples R China;[3]Shanghai Inst Aircraft Mech & Control, Shanghai, Peoples R China

年份：2026

外文期刊名：FATIGUE & FRACTURE OF ENGINEERING MATERIALS & STRUCTURES

收录：;EI(收录号：20262120767609);WOS:【SCI-EXPANDED(收录号:WOS:001771678200001)】；

基金：This work was supported by the National Natural Science Foundation of China (52475156, 52321002, and 12275176), the National Science and Technology Major Project (J2019-V-0010-0078), and the Shanghai Gaofeng Project for University Academic Program Development.

语种：英文

外文关键词：alloy 718; crack initiation mechanism; elevated temperature; stress-assisted oxidation; very high-cycle fatigue

摘要：The high-cycle fatigue (HCF) and very high-cycle fatigue (VHCF) behaviors of alloy 718 were investigated via ultrasonic axial cycling at room temperature (RT) and 650 degrees C. The lower bound stress amplitude (sigma a) for survival at 109 cycles was 618 MPa at RT and 475 MPa at 650 degrees C. Interestingly, two distinct crack initiation modes were identified at 650 degrees C, leading to significant life differences. When sigma a is lower than 520 MPa, single-crack initiation was observed, triggered by slip-induced deformation localization. In contrast, when sigma a >= 520 MPa, multi-crack initiation was facilitated by deformation localization and stress-assisted oxidation, where oxygen preferentially reacted with grain boundary delta phases, forming brittle oxides. In addition, fatigue data were incorporated into the modified Yang et al.'s model, showing life factors within +/- 2.5 for single-crack initiation samples but +/- 3.5 for multi-crack initiation samples. This study emphasized the critical role of stress-assisted oxidation in high-temperature life prediction.