Enhancement in the elongation, yield strength and magnetic properties of intermetallic FeCo alloy using spark plasma sintering

Equiatomic FeCo alloys were densified using spark plasma sintering (SPS). Using a constant 50 MPa pressure, the sintering temperature and dwell times for the SPS process were optimised for different heating rates (50, 100, 300 °C min−1). All samples used in this optimisation process were analysed in terms of their mechanical and magnetic properties. Interestingly, for all heating rates, FeCo samples sintered at the highest temperatures (1100 °C) without dwelling exhibited an increased tensile yield strength combined with an improvement in the elongation to fracture. This occurred despite the microstructural coarsening observed at this sintering temperature, which decreased the ultimate tensile strength. Improved grain boundary bonding in the samples sintered at the highest sintering temperature led to a suppression of intergranular fracture, something previously considered to be inherent to all equiatomic FeCo alloy structures. An optimum combination of mechanical (ultimate tensile strength = 400 MPa, yield strength = 340 MPa and strain to failure = 3.5%) and magnetic (saturation induction (B sat) of 2.39 T and coercivity (Hc) of 612 A m−1) properties was achieved by sintering to 1100 °C using a relatively slow heating rate of 50 °C min−1 with no dwell time.