Abstract Crack initiation mechanisms in the very high cycle fatigue (VHCF) regime of nickel-based single-crystal (SX) superalloys have been investigated at high temperature (1000 °C) and under fully reversed conditions (R = −1). For all Ni-based SX alloys tested, a discernible area called rough zone has been identified around the crack initiation site on the fracture surface and is for the first time described. By means of electron microscopy and atom probe analyses, localized and severe plastic activity occurring in the rough zone is evidenced. The high dislocation density provided by the slip bands induces single-phase recrystallized grains and phases precipitation (intermetallics or carbides) via the redistribution of interacting solutes in the rough zone. A crack initiation mechanism based on these observations and on the stress intensity parameter determined around the rough zone – which has been demonstrated to be a constant threshold dependent on the material – is finally proposed.

中文翻译：

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镍基单晶高温合金高温高周疲劳裂纹萌生机制

摘要 镍基单晶 (SX) 高温合金在超高周疲劳 (VHCF) 状态下的裂纹萌生机制已在高温 (1000 °C) 和完全反向条件 (R = -1) 下进行了研究。对于所有测试的镍基 SX 合金，在断裂表面的裂纹萌生点周围已经确定了一个称为粗糙区的可辨别区域，这是第一次描述。通过电子显微镜和原子探针分析，证明了在粗糙区域发生的局部和严重的塑性活动。滑移带提供的高位错密度通过粗糙带中相互作用溶质的重新分布诱导单相再结晶晶粒和相沉淀（金属间化合物或碳化物）。