MEASUREMENT OF THE ENTHALPY AND SPECIFIC-HEAT OF UNDERCOOLED NICKEL AND IRON MELTS

Detailed knowledge of the thermodynamic properties in the metastable regime of undercooled melts is of essential interest in a variety of aspects: short-range order in liquids, description of nucleation and crystal growth, and the glass transition. A drop calorimeter has been developed which allows in combination with electromagnetic levitation melting to measure the temperature dependence of the enthalpy, H(T), and the specific heat, C(p)1(T), over an extended range of undercooling, DELTAT. The first results obtained for pure Ni and Fe are reported. In the undercooled regime, no deviations from the linear correlation H(T) above the melting point are observed. The results of C(p)1 are compared with those obtained by another method of determining the limits of hypercooling DELTAT(hyp) = DELTAH(m)/C(p)1,int (DELTAH(m) is the heat of fusion, C(p)1,int is the integral heat capacity of the undercooled melt).