Crystallization kinetics of Co58-xMn20Gex(BSi)22 metallic glasses

Abstract

Germanium was introduced at different fractions (5 and 10 at %) into the Co58Mn20B10Si12 alloy to study its effect on the crystallization behavior of the amorphous alloy. It was shown that the Ge addition delayed the onset of devitification by ~20℃, forcing the primary crystallization to nearly coincide with the subsequent eutectic reaction. Metastable SiB6 was observed to co-nucleate with Co2Mn(SiGe) due to the Si rejection from Co2Mn(SiGe) when annealed at 550℃ for both alloys. In addition, Co48Mn20Ge10B10Si12 exhibited a pronounced structural relaxation behavior which was absent in the Ge-free Co-Mn alloys. Estimation of the activation energies showed that increasing Ge addition forced the crystallization kinetics progressively sluggish. We demonstrated that the Ge addition to the Co-Mn amorphous alloy had substantial effects both on the crystallization path and on the kinetics, which well correlated to the ensuing magnetic properties of the thermally annealed Co-Mn-Ge amorphous alloys.