Effect of melt temperature on the formation of air pockets during splat quenching

Abstract

The effect of melt temperature on the formation of air pockets at the contact surface of the ribbons was studied. An alloy with a melting point slightly higher than room temperature (320 K) was used and was heated to 353, 573 and 773 K, respectively, to investigate the thermal effect of the melt temperature on the gas. Under high casting velocity (20 ms−1) and extremely low melting temperature (353 K), the air pockets were slender and parallel to the casting direction. The liquid melts with a higher casting temperature (773 K) induced coarse air pockets at various casting velocities, and the air pockets were coarser than those induced by the pressure of the gas boundary layer only. The heat flow analysis showed that the local pressure of the entrapped gas, built up by the thermal effect and assuming constant volume, is far greater than the pressure by the gas-boundary layer effect. Thus the thermal effect of the liquid melt should be taken into account in the formation of air pockets during splat quenching.