Heterogeneous nucleation and solidification prediction of Sn-Pb alloy droplets

The Sn-5% Pb droplets with sizes of 150 and 185 mum were generated by Uniform Droplet Spray (UDS) under N-2 atmosphere with 1.36 mumol/L oxygen. The appearance of Sn-5% Pb droplets under the optical microscope showed that the droplets are uniform and spherical. The method employed non-adiabatic calorimetry to determine the nucleation point and undercooling of droplets. The fraction covered by oxide was calculated as a function of time and temperature. The model for heterogeneous nucleation catalyzed by oxidation on the droplet surface was developed, which was a reasonable expression of the heterogeneous nucleation and solidification behavior of Sn-Pb droplets. The CCT curves were computed using above experimental results under the heterogeneous surface nucleation of droplet. The same model can be applied to predict the heterogeneous nucleation behavior of the droplets for any type of cooling schedule. The calculation results are very reliable based on the experimental data.