Effect of deformation heterogeneity on development of geometrically necessary dislocation density in heterogeneous-structured CrMnFeCoNi high-entropy alloy

Heterogeneous-structured high-entropy alloys (HEAs) overcome strength-ductility trade-off, demonstrating potential for a wide range of applications in aerospace, defense and military fields. In this work, the evolution of geometrically necessary dislocation (GND) density in a heterogeneous-structured CrMnFeCoNi HEA is investigated at different strains. This HEA consists of fine- and coarse-grained domains. GND density measurements are performed using electron backscatter diffraction. GND density increases significantly in the fine-grained domains while increases slightly in the coarse-grained domains. The disparity of GND density between the coarse and fine grains indicates a distinct deformation gradient, which is related to back-stress strengthening. At 7% strain, the GND density in the fine-grained domains reaches parity with that in the coarse-grained domains, indicating a transition from single slip to multiple slip. The local misorientation distributions are described by a lognormal function.