A Method Based on Radiative Cooling for Detecting Changes in Undercooked Metallic Liquids

We introduce a structure-sensitive parameter for unclercooled melts which can be measured in containerless We have established that the ratio, R(T), emissivity eT(T) to constant-pressure specific processing experiments. of hemispherical total heat CP(T) can serve as an indicator which is sensitive to any changes in short range atomic order in undercooked metallic melts. R(T) = E~(T)/c P(T) values for nickel, zirconium, and silicon have been obtained using the high temperature electrostatic levitator while the levitated melts were undergoing purely radiative cooling into the deeply undercooked region. R(T) plots for undercooked liquid nickel and zirconium indicate no significant change in short-range structure from their melting temperatures to 15% undercooking. In contrast, liquid ‘silicon shows marked short-range structural changes beginning above its melting temperature and extending throughout the undercooked region. The short-range structure of liquid silicon is related to the directional covalent The nickel and in support of metal bonding which characterizes its solid form. zirconium data show that ET varies linearly emissivity theories.