Effect of cyclic loading on the magnetic properties of FeCo-2V alloy

FeCo-2V soft magnetic alloys offer attractive properties for demanding electromagnetic applications. While their magnetic properties are well-characterised under static loading conditions, the evolution of these properties under cyclic mechanical loading, as seen in service, remains insufficiently explored. This study examines how fatigue deformation alters the magnetic behaviour of an FeCo-2V alloy. The investigation employed strain-controlled cyclic loading combined with Single Sheet Tester measurements across multiple frequencies. A modified Bertotti loss separation analysis quantified the contributions of hysteresis and eddy current losses to total core loss. Experimental results demonstrated an increase in coercivity, and significant core loss increase during early-stage fatigue, followed by more gradual changes at higher cycle counts. The abrupt initial property changes correlate with rapid dislocation accumulation, while subsequent stabilisation reflects saturated defect densities. Notably, hysteresis losses dominated the degradation, while eddy current losses remained stable throughout cycling. These findings establish clear relationships between cyclic loading and magnetic properties in FeCo-2V and may serve as the basis for non-destructive fatigue assessment through magnetic measurements. • In situ synchrotron X-ray diffraction, EBSD and DIC were used to investigate Lüders bands in FeCo-2V. • Lüders band propagation was characterised through strain maps and peak broadening patterns. • EBSD-KAM analysis revealed dislocation accumulation in band-affected regions. • Williamson–Hall analysis quantified rising inhomogeneous strain with macrostrain.