Heterogeneous influences on the crystallization of Pd 43 Ni 10 Cu 27 P 20

The influence of ingot purity as well as B2O3 fluxing on the crystallization of undercooled Pd43Ni10Cu27P20 is studied in a differential scanning calorimeter. B2O3 fluxing strongly influences the isothermal crystallization behaviour at temperatures above the nose in the time-temperature-transformation diagram. The ingot purity, in contrast, affects the isothermal crystallization at low temperatures but leaves the crystallization at high temperatures relatively unaltered. Thermal analysis, together with microstructure investigations of samples processed and prepared under different conditions, suggests two sources of heterogeneous nucleation. One source is surface impurities, which can be passivated by fluxing with B2O3. The other consists of impurities from the ingot materials homogeneously distributed within the sample. Crystallization at high temperatures is controlled by the formation of one nucleus, preferentially formed at the surface, which can be suppressed to a large extent by B2O3 fluxin...