Thermal analysis of copper-tin alloys during rapid solidification

A series of solidification experiments using a mirror furnace and a levitation technique were performed on different Cu-Sn alloys. Cooling curves during solidification were registered using a thermocouple of type K connected to a data acquisition system. The undercooling, cooling rates of the liquid and of the solid state, solidification times and temperatures were evaluated from the curves. The samples were found to solidify far below the liquidus temperature. The cooling curves for different samples and alloys were simulated using a FEM solidification program. The heat transfer coefficient, heat of fusion and specific heat were evaluated. It was found that the calculated values of the heat of fusion were much lower than the tabulated ones. The calculated values of the specific heat in the solid state were also found to be much higher than those quoted in the literature, especially for the mirror furnace experiments. The effect of rapid cooling on the thermodynamic state and the solidification process of the alloys has been evaluated. The effect of cooling rate on the formation and condensation of vacancies is discussed. It is proposed that a large number of vacancies form during rapid solidification and that they condense during and after the solidification. The influence of these defects on the thermodynamics and solidification of the alloys has been evaluated.