Influence of Mechanical Loading and Temperature on the Magnetic Properties of FeCo-2V Soft Magnetic Alloy
This thesis presents an investigation into the mechanical and magnetic responses of FeCo-2V alloy under various loading and thermal conditions, aiming to elucidate the mechanisms behind magnetic property degradation during service. By integrating advanced characterisation techniques, including in situ Digital Image Correlation (DIC), Electron Backscatter Diffraction (EBSD), synchrotron X-ray diffraction, Single Sheet Tester (SST) measurements, and magnetic loss analysis, this work offers a multiscale perspective on the relationship between mechanical deformation, microstructural evolution, and magnetic performance. Initial studies revealed that Lüders band formation is driven by dislocation-induced strain localisation, as shown by DIC and EBSD-KAM analysis. These findings were reinforced by synchrotron XRD and Williamson–Hall results, which confirmed that Lüders band propagation is accompanied by inhomogeneous strain development. Magnetic characterisation further demonstrated that dislocation accumulation increases coercivity and hysteresis losses, providing a clear mechanism for the degradation observed in mechanically strained magnetic materials. In situ magnetic testing under uniaxial stress revealed a stress-dependent response: moderate tensile stress enhanced magnetic performance, whereas higher tensile or compressive stresses led to deterioration. Under cyclic loading, magnetic losses progressively increased in conjunction with fatigue-induced microstructural changes, indicating the potential of magnetic measurements as non-destructive indicators of fatigue damage. Additionally, elevated temperatures were found to reduce core losses, attributed to decreased magnetic anisotropy energy and increased resistivity. This work addresses a critical gap in understanding magneto-mechanical coupling in FeCo-2V alloys and provides fundamental knowledge for improving the design, processing, and operational reliability of soft magnetic materials. The findings have significant implications for future applications in high-performance electromechanical systems, where mechanical stress and temperature must be carefully managed to preserve magnetic efficiency.
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