Effect of Heat Treatment Conditions on the Magnetic and Mechanical Properties of Hard Magnetic Isotropic Fe–28Cr–15Co Alloys Containing Molybdenum and Niobium

The magnetic characteristics and compressive mechanical properties of hard magnetic isotropic Fe–28Cr–15Co–2Mo and Fe–28Cr–15Co–2Nb powder alloys subjected to heat treatment are studied. The heat treatment includes the isothermal holding at the temperatures Tiso = 630–645°C, subsequent two-stage cooling from the Tiso temperature at a rate of 20°C/h for 3 h to a temperature of 500°C at a rate of 8°C/h, and final furnace cooling. The Fe–28Cr–15Co–2Nb alloy is found to have a higher residual induction Br of up to 0.95 T, and the Fe–28Cr–15Co–2Mo alloy has a higher coercive force Hc of up to 40.8 kA/m. Moreover, the highest values of the maximum energy product (BH)max for these alloys are almost close and equal to 12.3–12.4 kJ/m3. The yield strength of the heat-treated Fe–28Cr–15Co–2Nb alloy is 1.5–1.6 times higher than that of the Fe–28Cr–15Co–2Mo alloy, i.e., σ _0.2^c is equal to 1520–1620 and 960–1000 MPa, respectively. Both alloys are found to be plastic; no failure of the samples is observed during compression tests up to the strain εc = 20%.