Low cobalt CrCoFe and CrCoFe-X permanent magnet alloys

Abstract

CrCoFe alloys containing 3-10 w/o Co and CrCoFe-X alloys containing 2-5 w/o Co and 0.1-3.0 w/o of B, C, Ti, Ge or Hf were prepared and magnetically hardened by slow cooling in a magnetic field at rates varying from 0.4-6.2°C/h. The extent of magnetic hardening, as indicated by the coercive force, has been explained in terms of the spinodal decomposition temperature of the alloy. It has been found that the higher the spinodal decomposition temperature of the alloy, the faster is the cooling rate at which maximum magnetic hardening is observed. Quaternary additions were not found to be beneficial in that they did not enhance the kinetics of spinodal decomposition, and magnetically diluted the ternary alloys. Energy products as high as 5.3 MGOe, with B <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</inf> = 13.4kG and H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</inf> = 528 Oe, have been observed for the 5Co-30Cr-65Fe alloy.