In situ neutron diffraction study of fatigue behavior of CrFeCoNiMo0.2 high entropy alloy

In situ neutron diffraction measurement was applied to study the low-cycle fatigue behavior of CrFeCoNiMo0.2 high entropy alloy. A two-step stress-controlled fatigue test with a stress range of 100-460 and 20-500 MPa was employed. The as-cast sample was cycled 129,000 and 61,000 times, respectively, before fracture. The evolution of the lattice strain and peak intensity demonstrates that the main deformation mechanism is dislocation slip, while no evidence of stacking fault was found. A three-stage ratcheting was clearly observed. Under the stress-controlled mode, the experimentally determined dislocation density increases linearly with the ratcheting strain. The increase of the dislocation density results in a decay of the ratcheting strain rate, which stabilizes the structure and is beneficial for fatigue resistance.

Automated summary

In the low-cycle fatigue study of CrFeCoNiMo0.2 high entropy alloy, dislocation slip was identified as the main deformation mechanism, and a three-stage ratcheting behavior was observed. The increase in dislocation density due to ratcheting strain was found to stabilize the structure and improve fatigue resistance.