Multi-stage dwell fatigue crack growth behaviors in a nickel-based superalloy at elevated temperature
Multi-stage dwell fatigue crack growth behaviors in a nickel-based superalloy at elevated temperature
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DOI：
10.1016/j.engfracmech.2021.107859
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发表时间：
2021-08
影响因子：
5.4
通讯作者：
Ji Wang;Run-Zi Wang;Xian‐Cheng Zhang;Y. Ye;Yan Cui;H. Miura;S. Tu
中科院分区：
文献类型：
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作者：
Ji Wang;Run-Zi Wang;Xian‐Cheng Zhang;Y. Ye;Yan Cui;H. Miura;S. Tu
在Inconel 718中进行了一系列连续和间断循环试验，在650 °C下的停留时间范围为0 s至10，800 s，以研究多阶段停留疲劳裂纹扩展（DFCG）行为。采用双折射技术测量了从短周期到长周期的间歇性DFCG速率，并根据微观结构特征追溯了特定的损伤机制。从宏观角度，根据DFCG速率的趋势，将DFCG曲线分为短、中和长停留条件。相应地，保压疲劳寿命分布分为三个阶段，这三个阶段对保压时间的长短表现出不同的敏感性。结合EBSD成像和高分辨透射电镜分析，从微观角度对DFCG曲线中反映的高散射点进行了详细讨论。双晶界（twin boundaries，简称TBs）以其独特的性能被认为是抵抗DFCG的屏障。此外，随着保压时间的增加，主裂纹形态由穿晶型向沿晶型转变。同时，在高分散点的局部裂纹扩展模式从横向改变为沿着极低DFCG率的103 TB。此外，高角度裂纹偏转是导致DFCG率降低的另一个因素。
A series of continuous and interrupted cyclic tests in Inconel 718 with the dwell times ranging from 0 s to 10,800 s at 650 °C were carried out in order to study the multi-stage dwell fatigue crack growth (DFCG) behavior. Replica technique was used to measure the intermittent DFCG rates from short to long periods and to retrospect specific damage mechanisms based on microstructural characterizations. From the macroscopic viewpoint, the DFCG curves were classified into short, moderate and long dwell conditions according to the tendencies in DFCG rates. Correspondingly, the dwell fatigue life distribution was divided into three periods, which exhibit different sensitivities in the length of dwell time on dwell fatigue life. From the microscopic viewpoint, the high-scattered points reflected in the DFCG curves were elaborately discussed with the combinations of EBSD mapping and high-resolution TEM analysis. Σ3 twin boundaries (Σ3 TBs) were regarded as the barriers to resist the DFCG due to their special performances. In addition, with the increase of dwell times, the main crack morphologies changed from transgranular to intergranular mode. Simultaneously, local crack growth modes at high-scattered points changed from across to along the Σ3 TBs with extreme low DFCG rates. Also, high-angle crack deflection was another factor that was responsible for the decrease of the DFCG rates.