Relaxation, Crystallization and Consolidation of Amorphous Alloy Powders

The influence of applied pressure on the structural relaxation, glass transition, crystallization and consolidation for an amorphous phase was examined by using a typical glassy Pd₄₈Ni₃₂P₂₀ alloy in a spherical powder or a ribbon form. The Pd-Ni-P alloy was chosen because of the existence of a wide supercooled liquid region in the temperature range below crystallization temperature (T_x). The relaxation and crystallization are significantly suppressed by the application of compressive load, presumably because of the increase in viscosity and the decrease in diffusivity. As a result, the pressing at a high temperature of 0.97T_X is required to produce an amorphous bulk with high relative density. Furthermore, an intermediate annealing between pressings was found to be effective for the reduction of the enhanced viscosity. The multi-stage pressing treatment consisting of pressing and annealing enabled to produce a highly dense amorphous bulk even at a relatively low temperature near T_g.