Structural and Mössbauer investigations of the FeCoNiPd-X high entropy alloys

The concept of single-phase high-entropy alloys (HEAs) remains central to the design of advanced structural materials, due to the superior mechanical and functional properties associated with chemically disordered solid solutions. In this study, we investigate the effect of adding selected elements (Cu, V, Mn, Al, Ti) to the canonical equiatomic FeCoNiPd alloy, which crystallizes in a face-centered cubic (fcc) structure. The aim was to identify which elemental additions preserve the single-phase character and favorable structural properties of the parent alloy. Comprehensive characterization, including X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), and Mössbauer spectroscopy, was used to evaluate the phase stability, microstructure, and magnetic behavior of the resulting alloys. Among the tested compositions, only the Cu- and V-containing alloys retained the single-phase fcc structure, while the addition of Mn, Al, or Ti led to multiphase systems. These findings demonstrate that Cu and V are promising candidates for compositional tuning of FeCoNiPd-based HEAs without compromising their structural simplicity, offering valuable insights into the design of chemically stable multicomponent alloys.