Extremely low critical cooling rates of new Pd-Cu-P base amorphous alloys

A new Pd40Ni10Cu30P20 amorphous alloy subjected to the B2O3 flux treatment was found to have a maximum thickness above 50 mm and a low critical cooling (Rc) of 0.100 K s−1, The Rc for the Pd-Ni-Cu-P alloy without the flux treatment is 1.58 K s−1 and the decrease in Rc is due to the suppression of heterogeneous nucleation, in addition to the high Tg/Tm of 0.72 and ΔTx( =Tx − Tg) of 98 K. These Rc values are smaller and the Tg/Tm and ΔTx values are larger as compared with those (Rc = 140 K s−1, Tg/Tm = 0.67 and ΔTx = 63 K) for an unfluxed Pd40Ni40P20 amorphous alloy. The new alloy appears to lie around the eutectic point with a low Tm of 804 K and the crystallization occurs through a single stage accompanying the precipitation of Pd2Ni2P, Pd15P2, (Ni, Cu)3P and unknown compound. The finding of the new amorphous alloy with the lowest Rc and the largest thickness is important for the future development of bulk amorphous alloys.