Phase transformation and magnetic properties of annealed Fe52.2Co46V1.8 alloy

In this work, FeCoV alloys were annealed in vacuum at various temperatures for different time, with and without applying an external magnetic field, respectively. The effect of the annealing on their magnetic properties has been investigated in regard with microstructural characterizations. X-ray diffraction analysis shows that the alloy is characterized of α-Fe bcc structure. It has been found that an order-disorder phase transformation took place locally in the surface around 993K. In addition, α-γ phase transformation occurs at the same temperature at which the Curie point is observed in the TG curve. Coercivity is decreased with increasing annealing temperatures, and changed from about 3.2kA/m to 78A/m when the annealing temperatures are increased to 1173K. Microstructural observations show that the decrease of coercivity after annealing is contributed mainly by grain growth. The coercivity of the alloy is further decreased by 32A/m after magnetic field annealing at 1033K. Hysteresis loops of the alloys after field annealing at 1033K featured more rectangular shape with smaller coercivity, compared with those after vacuum annealing.