1992 Volume 56 Issue 11 Pages 1229-1234
The viscosity of liquid Fe-B-Si alloys has been measured by an oscillating crucible method in the temperature range from melting temperature (Tm) to about 1600 K. The viscosity of these alloys depends strongly on the composition. When the composition is located near a eutectic depression, the viscosity and the activation energies for viscous flow are drastically decreased, e. g., the activation energies obtained are 18.5, 32.2 and 50.9 kJ/mol for Fe79.5B12Si8.5 (near eutectic region), Fe81B11Si8 (hypoeutectic region) and Fe75B15Si10 (hypereutectic region), respectively. This may be due to the existence of some short range orders in the liquid, i. e., when the composition departs from the eutectic, Fe-rich order in the hypoeutectic region and Fe2B type order in the hypereutectic region are developed. These orders are suspended in the liquid and increase the viscosity and the activation energies. The viscosity below Tm is estimated from the Fulcher relation, i. e., ln η=−3.6582+734.1/(T−674) for Fe79.5B12Si8.5 and ln η=−4.1928+1934.1/(T−706) for Fe75B15Si10 where η: poise and T : K.
