On the viscosity of the amorphizing Co-(Cr,Fe)-Si-B melts

The study of the temperature and time viscosity dependences of the amorphizing Co_65.5Fe_6.5Si₁₈B₁₀, Co_65.5Cr_6.5Si₁₈B₁₀, Co₆₉Cr₃Si₁₈B₁₀ melts has been performed. It has been shown that the temperature and time viscosity dependences for each alloy are of the same nature. The anomaly attended by the changing of the energy activation of the viscous flow has been first determined in the viscosity polytherms under heating conditions in the vicinity of t* (t* is the characteristic temperature for each alloy, i.e. the temperature of the anomaly on the polytherm of the viscosity). This anomaly is caused by the change of the short-ordering type in the liquid phase in this temperature region as well as by the transition of its low-temperature structure into the high-temperature one. The latter being further cooled is retained up to the solidification temperatures and results in the viscosity hysteresis. It has been shown that the decrease of the alloying element concentration results in a substantial displacement of the anomaly temperature, t*, to the lower temperature region (t*=1360°C for Co_65.5Fe_6.5Si₁₈B₁₀, Co_65.5Cr_6.5Si₁₈B₁₀ and 1220°C for Co₆₉Cr₃Si₁₈B₁₀).