Magnetic Hysteresis Properties of Isotropic Hard Magnetic Fe–Cr–Co Compositions Alloyed with Tungsten

Abstract

Hard magnetic Fe–30Cr–20Co (wt %) compositions alloyed with to 3 wt % tungsten are obtained by powder metallurgy. The studies of the magnetic properties show that tungsten additions increase coercive force H_c and maximum energy product (BH)_max but decrease remanence B_r. This effect increases as the tungsten content in the material increases. The maximum values of H_c (55.8 kA/m) and (BH)_max (17.2 kJ/m³) are observed for the alloy with 3 wt % W. In this case, the alloys investigated in the present study were found to be sensitive to heat-treatment conditions. According to X-ray diffraction data, the alloys subjected to a complete heat treatment cycle are characterized by the presence of a marked fraction of the nonmagnetic γ phase; however, in this case, the magnetic properties correspond to those observed for analogous as-cast alloys. In the course of compression tests, all compositions alloyed with tungsten fail before reaching a strain of 20%, whereas, under the same condition, the unalloyed Fe–30Cr–20Co (wt %) composition is deformed without failure. Thus, tungsten additions decrease the plasticity of the material.