Crystallization of Co58-xMn20GexB10Si12 (x=5, 10) metallic glasses

Abstract

Germanium was introduced at different fractions (5 and 10 at.%) into the Co58Mn20B10Si12 (numbers indicate at.%) alloy to study its effect on the crystallization behavior of the amorphous alloy. It was shown that the Ge addition delayed the onset of devitrification by similar to 20 degrees C, 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 degrees C 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.