Influence of Wheel Surface Velocity and Ejection Gas Pressure on the Thickness of Amorphous Ribbon Produced by Planar Flow Casting in Vacuum

Abstract

Casting examination was carried out to investigate the influence of wheel surface velocity and ejection gas pressure on the thickness of ribbon produced by Planar Flow Casting in vacuum. Fe_80.5Si_6.5B₁₂C₁ (amorphous forming alloy) was cooled rapidly on a wheel made of Cu-1 mass%Cr under the pressure of 10⁻³ Pa. Nozzle orifice dimension was 0.6 mm×12 mm. As the wheel surface velocity increased, the thickness of ribbon obtained decreased. The thickness of the ribbon is determined by contact time between melt puddle and the wheel surface. The contact time (τ) is written as, τ=L_p⁄V where L_p is the length of the melt puddle in the direction of wheel revolution and V is the wheel surface velocity. Thus, the contact time depends on the length of the melt puddle in the direction of wheel revolution and the wheel surface velocity. Observations of the melt puddle with an optical microscope and a video camera indicated that the length of the melt puddle decreased as the wheel surface velocity increased. On the other hand, the thickness of the ribbon increased as the ejection gas pressure increased. The increase of the ejection gas pressure seems to cause the increase of the amount of the molten alloy ejected from the nozzle. Actually, it was found from the observations of the melt puddle that the length of the melt puddle increased as the ejection gas pressure increased. Further, the increase in solidification rate with increasing ejection gas pressure also increases the ribbon thickness.