Partial substitution of Co and Ge for Fe and B in Fe-Zr-B-Cu alloys: microstructure and soft magnetic applicability at high temperature

The partial substitutions of Co for Fe and Ge for B are studied for a Fe83 - xCoxZr6B10 - yGeyCu1 alloy series (x = 0, 5 and 20; y = 0 and 5) as a possible way of enhancing the high temperature applicability of NANOPERM alloys. The devitrification process, the nanocrystallization kinetics and the nanocrystalline microstructure are similar for all the studied alloys. Good soft magnetic properties are observed even at a high crystalline volume fraction of body-centered cubic (alpha)-Fe nanocrystals, which are stable up to ~1000 K. The partial substitution of Co for Fe is very effective to increase the Curie temperature of the residual amorphous matrix (TAMC). Although the substitution of Ge for B is ineffective to increase (TAMC), a clear increase of the saturation magnetization with respect to the Ge-free alloy can be observed.