Studies on relative catalytic efficiencies of zinc and aluminium on nucleation of dispersed bismuth droplets

In Zn-Bi and Al-Bi systems, both of which belong to monotectic class, dispersion of second phase particles within the matrix have been produced through rapid solidification processing (RSP) route. In order to understand relative catalytic efficiencies of Zn and Al matrices in catalyzing nucleation of Bi particles entrapped in the respective metal matrices, thermal analysis in constant program mode was performed. Thermal analyses revealed that Bi undercools by 132° in Zn matrix and by 157° in Al matrix. Thermodynamic barrier to nucleation (ΔG*) for Bi has also been calculated, which is 39·8 kcal/mole and 47·085 kcal/mole, in Zn and Al matrices, respectively at the maximum recorded undercoolings.