The high-cycle fatigue (HCF) properties and deformation behavior of additively manufactured equiatomic CoCrFeMnNi high-entropy alloys (HEAs), strengthened by in-situ formed oxides, were investigated. A CoCrFeMnNi HEA manufactured by selective laser melting (SLM) had a heterogeneous grain structure and dislocation network-induced sub-structures. Furthermore, nanosized oxides dispersed at the sub-structure and grain boundaries of SLM-built HEA. The results of tensile tests indicated that this SLM-built HEA had superior yield strength of 774.8 MPa with an elongation of 30.8%. The S-N curves revealed that the resistance of the SLM-built HEA to HCF was extraordinarily high compared with that of a homogenized (conventional casting + hot rolling + heat treatment) HEA. The corresponding fatigue limits of the SLM-built and homogenized HEAs were 570 MPa and 280 MPa, respectively. The excellent fatigue resistance of the SLM-built HEA is attributed to its unique microstructural characteristics (i.e., heterogeneous grain structures, dislocation networks, and in-situ formed oxides), and the deformation twins generated during cyclic load. The un-melted powder generated during the additive manufacturing (AM) process also contributed to the HCF resistance of the SLM-built HEA. Based on these findings, the correlations among the unique microstructure, internal defects, HCF properties, and fatigue fracture mechanism of the SLM-built HEA are also discussed.

研究了通过原位形成的氧化物增强的增材制造的等原子CoCrFeMnNi高熵合金（HEA）的高周疲劳（HCF）特性和变形行为。通过选择性激光熔化（SLM）制造的CoCrFeMnNi HEA具有异质晶粒结构和位错网络诱发的亚结构。此外，纳米级氧化物分散在SLM构建的HEA的子结构和晶界处。拉伸试验的结果表明，这种由SLM制成的HEA具有774.8 MPa的优异屈服强度，伸长率为30.8％。SN曲线表明，与均质（常规铸造+热轧+热处理）HEA相比，SLM制成的HEA对HCF的抵抗力极高。SLM建造的均质HEA的相应疲劳极限分别为570 MPa和280 MPa。SLM建造的HEA出色的抗疲劳性归因于其独特的微观结构特征（即异质晶粒结构，位错网络和原位形成的氧化物），以及在循环载荷过程中产生的形变孪晶。在增材制造（AM）过程中产生的未融化粉末也有助于SLM建造的HEA的HCF抗性。基于这些发现，还讨论了SLM建造的HEA的独特微观结构，内部缺陷，HCF特性和疲劳断裂机理之间的相关性。非均质的晶粒结构，位错网络和原位形成的氧化物），以及在循环载荷过程中产生的形变孪晶。在增材制造（AM）过程中产生的未融化粉末也有助于SLM建造的HEA的HCF抗性。基于这些发现，还讨论了SLM建造的HEA的独特微观结构，内部缺陷，HCF特性和疲劳断裂机理之间的相关性。非均质的晶粒结构，位错网络和原位形成的氧化物），以及在循环载荷过程中产生的形变孪晶。在增材制造（AM）过程中产生的未融化粉末也有助于SLM建造的HEA的HCF抗性。基于这些发现，还讨论了SLM建造的HEA的独特微观结构，内部缺陷，HCF特性和疲劳断裂机理之间的相关性。