Effect of Co Addition on the Structural Evolution and Magnetic Properties of Nanocrystalline Fe50Ni50-xCox Alloys Prepared by Mechanical Alloying

In this study, nanocrystalline Fe-Ni-Co ternary alloy powders with the composition of Fe50Ni50-xCox (x = 0-50) were prepared using a high-energy ball milling process after 30 h of milling time. Structure, microstructure, and magnetic properties were investigated in detail as a function of Co concentration using X-ray diffraction technique, scanning electron microscopy, vibrating sample magnetometer, and inductance/capacitance/resistance meter. The results indicate that BCC alpha-(Fe, Co) and FCC gamma-(Fe, Ni) single-phase solid solutions with average crystallite sizes of 15 and 10 nm were formed successfully in Fe50Co50 and Fe50Ni50 alloys, respectively. In addition, there is a mixture of two solid solutions of FCC and BCC phases in the range of Fe-Ni-Co ternary alloy composition (i.e., 5 < x < 45). When Co concentration increases from x = 0 to x = 50, the saturation magnetization and relative permeability improve towards the Fe50Co50 alloy value, while the coercivity worsens from 12.6 to 63.4 Oe.