Direct imaging of phase separation in Pd41.25Ni41.25P17.5 bulk metallic glasses

The alloy system, Pd41.25Ni41.25P17.5, has a negative heat of mixing among its constituent elements. By using high resolution transmission electron microscopy, high angle annular dark field in scanning transmission mode, and energy dispersive X-ray spectroscopy, it was found that phase separation occurs in Pd41.25Ni41.25P17.5 glassy alloys. For a clear exhibition of the amorphous phase separation reaction, it is desirable to introduce intermediate thermal annealing before an undercooled Pd41.25Ni41.25P17.5 melt is cooled down to become a solid amorphous specimen. The results suggest that there may be unique short range orders in amorphous/liquid Pd41.25Ni41.25P17.5, which are responsible for the phase separation.

► Direct experimental observations of amorphous phase separation in Pd41.25Ni41.25P17.5. ► Experimental techniques including, DSC, HREM, HAADF, and EDX. ► An intermediate annealing process before glass formation is essential.