Effect of Fe addition on the crystallization behaviour and Curie temperature of CoCrSiB-based amorphous alloys

Abstract

The crystallization behaviour and Curie temperature of melt-spun Co_{71− x} Fe _x Cr₇Si₈B₁₄ (x = 0, 2, 3.2, 4, 6, 8 and 12 at.%) amorphous alloys have been studied. Differential scanning calorimetry (DSC) showed two stages of crystallization. The first stage of crystallization (T _X1) in the alloy with 6 at.% Fe was the highest and it had the highest activation energy. X-ray diffraction studies revealed that the primary crystalline phase is hcp-(CoCr)₂Si for Fe-free alloy, whereas (CoFeCr)₂Si and (CoFeCr)₃Si phases were formed with the addition of Fe. hcp-Co was also formed along with these phases. The secondary crystalline phases were fcc-Co and various boron-rich phases. The Curie temperature of the alloys also changed with the addition of Fe to the system. Like the primary crystallization temperature, the Curie temperature of the alloys did not vary systematically with the Fe content. The addition of Fe to the Co-based system changes the nearest-neighbour interaction. This changes the exchange interaction between the transition metal elements. Due to the asymmetry in the Bethe–Slater curve, a systematic variation with Fe addition was not observed in the Curie temperature measurement.

Acknowledgements

The authors acknowledge and thank the Department of Science and Technology, Government of India, for funding part of this work. One of the authors (SK) is grateful to the Council of Scientific and Industrial Research for financial assistance.