Effect of annealing in hydrogen on composition, structure and magnetic properties of rapidly quenched Fe-Co-Si-TM-B ribbons

Recently, it was shown that boron can be extracted nearly completely from amorphous Fe-Si-B and Fe-Co-B ribbons by a two-step annealing in wet and dry hydrogen [1]. In this paper, we demonstrate that it is possible to extract boron from such ribbons by annealing only in dry hydrogen. Thus, the ribbons are prevented from being oxidized. This method is applied to Fe-Co-Si-TM-B-ribbons (TM = Mn, Cr), showing that it is possible to prepare boron free crystalline Fe-Co-Si-TM ribbons of such compositions which are not accessible by traditional metallurgy (casting, forging, rolling) because of their brittleness. Binary FeCo alloys with 5, 15 and 25 wt.% Co and an addition of 4.2 wt.% boron were prepared by planar flow casting. Successively, 3 - 6 wt.% of Fe were replaced by Si, Mn and/or Cr. The ribbons were annealed in flowing dry hydrogen at different temperatures and for different holding times. Boron escapes as a gaseous product and the detected compounds are HE, H2B, H3B and H6B2 The annealing effect on the microstructure of the amorphous ribbons was investigated by X-ray diffraction (XRD), scanning electron microscopic (SEM), and electron probe microanalysis (EPMA).