High-cycle fatigue behaviors of Al-Cr-Fe-Ni-V high-entropy alloy prepared by laser powder bed fusion: Roles of dislocation cell substructure and multi-precipitates

The fatigue performance of additively manufactured high-entropy alloys (HEAs) has gradually attracted extensive attention to extend the potential engineering application of HEAs. In the present research, a high-cycle fatigue (HCF) test was employed on the laser powder bed fusion (LPBF)-processed Al-Cr-Fe-Ni-V HEA in order to reveal the comprehensive effect of dislocation cells and multi-precipitates on the fatigue performance. Microstructural evolution (especially the dislocation cells and multi-precipitates) under cyclic loading was investigated systematically to explore the deformation mechanism of LPBF-processed HEA. During the cyclic loading, dislocations were continuously generated and interacted with the pre-existing dislocations, dislocation cells, and multi-precipitates. The dislocation interaction induced the formation of new dislocation cells in the cell-free regions. B2 precipitates also provide the frame support for the formation of new dislocation cells. Numerous dislocation cells could increase the ability to accommodate dislocations and relieve stress concentrations. Interaction between dislocations and dislocation cells also changed the configuration of cells and promoted the transformation from dislocation cells to subgrains, forming low-angle grain boundaries (LAGBs). LAGBs enhanced the slip continuity of the grain boundary, restrained strain localization, and contributed to the stability of fatigue deformation. Grain rotation and coordinated deformation of adjacent grains could delay crack initiation and enhance the fatigue damage limit. The combined effect of the structure mentioned above facilitated the relatively high fatigue resistance of the LPBF-processed HEA.