Magnetic Hysteresis and Mechanical Properties of Hard Magnetic Fe–27Cr–15Co–2Mo–Si–Ti–V Alloy

Magnetic hysteresis and mechanical properties of a hard magnetic alloy Fe–27Cr–15Co–2Mo–V–Si–Ti in an isotropic and anisotropic state are investigated with the help of the method of design of experiments for the purpose of developing a new hard magnetic material with increased values of residual induction B_r (isotropic state) and coercive force H_cB (anisotropic state). Optimization of the modes of heat treatment is performed by the creation of central composite design 2³ + star points. Statistical analysis of the data obtained makes it possible to ascertain the standard Pareto charts for B_r, H_cB, and (BH)_max values for isotropic and anisotropic alloys. Nonlinear regression equations for dependences of B_r, H_cB, and (BH)_max on variation factors are obtained, on the basis of which optimal regimes of heat treatment are determined. Magnetic hysteresis properties of Fe–27Cr–15Co–2Mo–V–Si–Ti alloy are enhanced significantly after an optimal heat treatment. As a result, a new hard magnetic material on the basis of the Fe–27Cr–15Co system is developed. In the anisotropic state, the values of residual induction, coercive force, and maximum energy product are B_r > 1 T, H_cB > 50 kA/m, and (BH)_max > 24 kJ/m³, respectively, whereas in the isotropic alloy they are B_r ~ 0.8 T, H_cB ~ 40 kA/m, and (BH)_max > 11.5 kJ/m³. Analysis of magnetic properties of specimens from the produced pilot batch of anisotropic Fe–27Cr–15Co–2Mo–V–Si–Ti magnets in the number of 51 pieces shows that the yield of magnets with H_cB > 45 kA/m is 100% and with H_cB > 50 kA/m is 83%.