Inability of precipitation-hardening to improve the fatigue limit of Ni-based superalloy 718 through a perspective of shear-mode cracking threshold
Inability of precipitation-hardening to improve the fatigue limit of Ni-based superalloy 718 through a perspective of shear-mode cracking threshold
复制标题
从剪切模式裂纹阈值角度看沉淀硬化无法提高镍基高温合金718的疲劳极限
DOI：
10.1016/j.matlet.2020.128377
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发表时间：
2020
影响因子：
3
通讯作者：
Hisao Matsunaga
中科院分区：
文献类型：
--
作者：
Yuya Tanaka;Saburo Okazaki;Yuhei Ogawa;Masahiro Endo;Hisao Matsunaga
众所周知，沉淀硬化材料的疲劳强度低于其高屈服强度和拉伸强度所预期的疲劳强度。为了阐明这种异常现象背后的原因，除了单轴疲劳试验之外，还对经过两种不同热处理（固溶退火和沉淀硬化）的镍基高温合金 718 样品进行了扭转疲劳试验。尽管两个样品之间的拉伸强度和屈服强度存在显着差异，但扭转疲劳强度彼此相当。这一结果是根据剪切模式下对疲劳裂纹萌生和扩展的抵抗力来解释的，这种抵抗力不能通过沉淀硬化来增强，因为局部滑移带内的持续位错运动会消耗析出物。
Fatigue strength of precipitation-hardened materials is well known to be lower than that expected from their high yield and tensile strengths. To elucidate the reasons behind such anomaly, torsional fatigue tests, in addition to uniaxial fatigue tests, were conducted on samples of the Ni-based superalloy 718, subjected to two different heat treatments (solution-annealing and precipitation-hardening). Despite the significant differences in tensile and yield strengths between the two samples, the torsional fatigue strengths were mutually equivalent. This result was interpreted in light of the resistance against fatigue crack-initiation and -propagation in shear-mode, which cannot be enhanced by precipitation-hardening due to the depletion of precipitates by persistent dislocations motion within localized glide-bands.