Effect of Recrystallization and Phase Transitions on the Mechanical Properties of Semihard Magnetic FeCo-7.15V Alloy During the Thermomechanical Process

Abstract

FeCo alloys (with 7 to 14 wt pct V) are industrially key engineering materials that play an outstanding role in applications requiring semihard magnetic materials. In this study, the effects of recrystallization and phase transitions on the mechanical properties of FeCo-7.15 wt pct V alloy, in the cold-rolled and annealed conditions, were investigated. Hence, cold-rolled Fe-Co-7.15V alloy (with 90 pct reduction in thickness) was annealed at different temperatures. The microstructural evolutions were observed by scanning electron microscopes, and mechanical properties were examined using microhardness and tensile tests. Experimental results showed that the mechanical properties of the alloy depend on several phase transitions, including recrystallization, allotropy, and ordering. It was found that this alloy is too brittle and difficult to fabricate in ordered condition, and depending on the annealing temperature, the order/disorder transition is responsible for the mechanical properties. Also, after annealing at temperatures higher than 723 K (450 °C) and up to 1023 K (750 °C), the γ phase was observed in the structure, so that by annealing at ~973 K (700 °C), the microstructural observation showed a duplex structure consisting of α + γ phases. In this condition, elongation was increased by an increase in the volume fraction of γ phase. Furthermore, the Young’s modulus of this alloy changed at various annealing temperatures as a function of texture evolutions.