Magnetic and mechanical properties of nanotwin SiO2-FeCoNi(AlSi)0.4 high entropy alloy prepared by mechanical alloying and spark plasma sintering

High-entropy alloys (HEAs), comprised of ferromagnetic metals such as Fe, Co, and Ni, demonstrate remarkable combinations of magnetic and mechanical properties. In this study, we explored the microstructure and magnetic characteristics of SiO ₂-FeCoNi(AlSi) _0.4 core–shell HEAs fabricated via mechanical alloying (MA) and spark plasma sintering (SPS). Thermodynamic analysis revealed that the FeCoNi(AlSi) _0.4 core–shell alloy system exhibits a higher ΔS (11.75 kJ/mol), indicating that forming a solid solution structure is easy. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses confirmed the development of a face-centered cubic (FCC) solid solution with a highly deformed nanotwin structure after SPS as-sintered. The vibrating sample magnetometer (VSM) test indicated an elevated soft magnetic behavior for FeCoNi(AlSi) _0.4 core–shell HEAs as-sintered, with a magnetic saturation (MS) of 140.2 emu/g and a coercivity field (HC) of 1.35 Oe in an applied magnetic field of 2 T. The ultimate shear strength and tensile strengths were found to be 1552.4 MPa and 1278.9 MPa, respectively. This investigation conclusively highlights that the lower fault energy of the FeCoNi(AlSi) _0.4 alloy system significantly influences the mechanical and magnetic properties of HEAs.