Preparation and thermal stability of bulk amorphous Pd40Cu30Ni10P20 alloy cylinder of 72 mm in diameter

The glass-forming ability of a Pd40Cu30Ni10P20 alloy was found to increase significantly by B2O3 flux treatment; as is evidenced by the decrease in the critical cooling rate from 1.57 K/s in the non-fluxed state to 0.100 K/s in the fluxed state. The flux treatment also causes the extension of the supercooled liquid region by the increase in the onset temperature of crystallization (T-x). The effect of the flux treatment is presumably due to the increase in the thermal stability of the supercooled liquid by the suppression of heterogeneous nucleation. The critical cooling rates in the non-fluxed and fluxed states for a Pd40Ni40P20 alloy are measured to be 128 and 0.167 K/s, respectively, both of which are larger than those for the Pd-Cu-Ni-P alloy. The use of the molten Pd-Cu-Ni-P alloy subjected to the Aux treatment enabled the production of bulk amorphous alloys in cylindrical forms of 50 to 72 mm in diameter and 52 to 75 mm in length. The glass transition temperature (T-g) and T-x values of the bulk amorphous alloys are the same as those for the melt-spun amorphous ribbon prepared from the fluxed molten alloy. The success of synthesizing an amorphous alloy of 72 mm in diameter is encouraging both for the future development of basic science of bulk amorphous alloys and for their engineering application.