The low-cycle fatigue properties of titanium alloys suffering cyclic loading determines the safety in service for their components used in submarine shells. It has been reported that tensile property could be improved by making use of Fe alloying element partitioning effect. However, the fatigue property and mechanism of titanium alloys with Fe addition remain unknown. In this study, the low-cycle fatigue property and cyclic deformation mechanism of Ti–6Al–4V-0.55Fe and Ti–6Al–4V ELI with a duplex microstructure were systematically investigated. With the addition of Fe element, Ti–6Al–4V-0.55Fe with longer lasting cyclic hardening behavior and lower cyclic softening rate, showed higher fatigue life under selected strain amplitudes. Under low strain amplitude, effect of Fe on dislocation motion, interface resistance, lattice distortion, and micro strain were responsible for the enhanced fatigue life. While under high strain amplitude, Fe brought out the pinning effect on interface. Besides, Fe addition also limited the fatigue crack propagation.
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