Development and sythesis of magnetic high entropy alloys

High Entropy Alloys (HEAs) are unique and new advanced metallic alloy systems, especially for aerospace and defense industries due to their superior and impressing mechanical, physical, electrical and magnetic properties. This thesis focuses on synthesis and development of magnetic HEAs and the investigation of magnetic properties, phase formation mechanisms, thermal stability, and mechanical properties of Fe-Co-Ni-Al-X (X= Ti, V, Nb) alloy systems under both as-cast and isothermally annealed conditions. The alloy designed were first done due to thermodynamic data calculations and then high purity elements were used to produce the alloys using vacuum arc melter. The high entropy alloys were characterized using X-ray diffraction (XRD), optic microscope (OM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), vibrating sample magnetometer (VSM), and hardness tester. The analysis shows the effect of constituent elements on the phase formation, magnetic and mechanical properties of Fe-Co-Ni-Al-X (X: Ti, V, Nb) alloy systems. It was found that the increase in Co concentration increases the magnetic saturation and decreases the coercive force. On the other hand, Cu and Ti has little significance on reducing the coercive force. The isothermal annealing processes are found to improve magnetic properties of the alloys. The isothermally annealed alloys at 928 K for 24 hours show phase t3ransformations in comparison to their as-cast and isothermally annealed conditions at 928 K for 3 hours. The Vickers microhardness analysis show similar values for all as-cast alloys. The hardness values are found to increase with isothermal annealing of all alloys for 3 hours, but there are no significant changes for 24 hours isothermal annealing. The analysis reveals the effect of Ti, V and Nb on microstructure and magnetic properties of Fe-Co-Ni-Al-X (X: Ti, V, Nb) alloy systems. Ti addition improves the magnetic properties of the alloys. V and Nb additions effect the microstructure and result in phase transitions of the alloys while the magnetic properties of the alloys are negatively affected by the addition of V and Nb.