UNDERCOOLING AND FORMATION OF SUPERSA-TURATED SOLID SOLUTION OF Pd-Ni-P IN A 20m DROP TUBE
20m落管中Pd-Ni-P合金的过冷与过饱和固溶相的形成

Undercooling behavior of Pd43.5Ni43.5P13 alloy was studied in a 20m drop tube. The solidified droplets were spheres with size ranged from 0.2 to 2.5 mm in diameter. The samples were examined by X-ray diffraction, scanning electron microscopy and X-ray energy dispersive spectrum. The results showed that when the alloy solidified in nitrogen at pressure of 1.8×104Pa, a near single phase of Pd-Ni-P fcc solid solution was obtained. This fact suggests that a partitionless solidification may occur during the solidification of the alloy in free fall. In addition, when the droplets solidified in nitrogen at pressure of 8.0×104Pa, an amorphous phase presented in the sample. This indicate that the sample had partially undercooled below the glass transition temperature Tg.