New Ductile Permanent Magnet of Fe-Cr-Co System

Abstract

The magnetic properties during tempering of Fe‐ 30∼50wt% Cr‐ 10 ∼30wt% Co alloys, which consist of bcc high‐temperature phase (α) obtained by quenching from 1300°C, have been measured. Alloys in a certain range of composition showed desirable permanent‐magnetic properties by a step‐tempering following a thermomagnetic treatment. An Fe‐ 31wt% Cr‐ 23wt% Co alloy, which was tempered at 600°C for 2 hrs and subsequently at 580°C for 4 hrs after an isothermal treatment at 640°C for 1/2 hr in a magnetic field of 4000 Oe, had $\mathrm{Br}\text{=11500\hspace{0.17em}}\mathrm{G}$ , $\mathrm{bHc}\text{=660\hspace{0.17em}}\mathrm{Oe}$ and $(\mathrm{BH})\max \text{=\hspace{0.17em}4.1\hspace{0.17em}}\mathrm{MGOe}$ . In addition to these desirable magnetic properties, the alloys could be forged at above 1000 °C. Moreover, they were ductile in quenched state and could be also cold‐worked. It may be assumed that the high coercive force arises from fine iron‐rich precipitates produced by a spinodal reaction.