Abstract

In this study, we examined the effect of deformation twins and dislocation cell structures on the fatigue properties of the CoCrFeMnNi high-entropy alloy using rotational bending fatigue tests. The dislocation cell structures and deformation twins were generated by prestraining the CoCrFeMnNi high-entropy alloy at room temperature (27 °C) and a cryogenic temperature (− 196 °C), respectively. To eliminate the effect of different material strengths on fatigue behavior, the tensile strengths of the specimens evaluated in the fatigue tests were kept similar by controlling the prestraining under room and cryogenic temperatures. The results of the rotational bending fatigue tests revealed that the CoCrFeMnNi high-entropy alloy prestrained at room temperature exhibited higher fatigue resistance and fatigue limit than the specimen prestrained at a cryogenic temperature. A small quantity of large micro-voids was formed at the triple junction of the grain boundaries in the specimen prestrained at room temperature, whereas a large quantity of small micro-voids was formed in the region where the deformation twins intersected the grain boundaries in the specimen prestrained at a cryogenic temperature. Therefore, it is concluded that the different aspects of micro-void formation affected the crack initiation and, consequently, the fatigue properties of the room and cryogenic temperature-prestrained alloys.

Graphic Abstract

中文翻译：

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微观结构特征对室温和低温下变形的CoCrFeMnNi高熵合金高循环疲劳行为的影响

摘要

在这项研究中，我们使用旋转弯曲疲劳试验研究了变形孪晶和位错胞结构对CoCrFeMnNi高熵合金疲劳性能的影响。通过分别在室温（27°C）和低温（-196°C）下对CoCrFeMnNi高熵合金进行预应变来生成位错单元结构和形变孪晶。为了消除不同材料强度对疲劳行为的影响，通过控制室温和低温下的预应变，使在疲劳测试中评估的试样的拉伸强度保持相似。旋转弯曲疲劳试验的结果表明，在室温下预应变的CoCrFeMnNi高熵合金比在低温下预应变的样品具有更高的抗疲劳性和疲劳极限。在室温下预应变的试样中，在晶界的三重结处形成了少量的大微孔，而在变形孪晶与晶界相交的区域中形成了大量的小微孔。样品在低温下预应变。因此，得出的结论是，微孔形成的不同方面影响了裂纹的萌生，进而影响了室温和低温温度受限合金的疲劳性能。在室温下预应变的试样中，在晶界的三重结处形成了少量的大微孔，而在变形孪晶与晶界相交的区域中形成了大量的小微孔。样品在低温下预应变。因此，得出的结论是，微孔形成的不同方面影响了裂纹的萌生，进而影响了室温和低温温度受限合金的疲劳性能。在室温下预应变的试样中，在晶界的三重结处形成了少量的大微孔，而在变形孪晶与晶界相交的区域中形成了大量的小微孔。样品在低温下预应变。因此，得出的结论是，微孔形成的不同方面影响了裂纹的萌生，进而影响了室温和低温温度受限合金的疲劳性能。

图形摘要