HIGH PACKING DENSITY OF ZR-BASED AND PD-BASED BULK AMORPHOUS-ALLOYS

With the aim of evaluating a packing density of the new bulk amorphous alloys, the densities of bulk Zr60Al10Cu30, Zr55Al10Cu30Ni5 and Pd40C u30Ni10P20 alloys were measured in cast amorphous and annealing-induce d crystallized states. The densities of the as-cast amorphous and crys tallized phases were measured to be respectively 6.72 and 6.74 Mg/m(3) for the Zr-Al-Cu alloy, 6.82 and 6.85 Mg/m(3) for the Zr-Al-Cu-Ni all oy, 9.27 and 9.31 Mg/m(3) for the Pd-Cu-Ni-P alloy. The annealing lead ing to the fully relaxed amorphous state induced slight increases of d ensity to 6.83 Mg/m(3) for the latter Zr-based alloy and to 9.28 Mg/m( 3) for the Pd-based alloy. The increase in density due to crystallizat ion is evaluated to be in the range of 0.30 to 0.54% which is much sma ller than that (2 to 3%) for the previously reported amorphous alloys. This result indicates that the new bulk amorphous alloys have more pa cked atomic configurations than ordinary amorphous alloys which requir e high cooling rates above 10(4) K/s for glass formation. It is theref ore thought that the higher packing density achieves the high glass-fo rming ability through the decrease of atomic diffusivity and the incre ase of viscosity. The present information obtained from the density da ta is consistent with the previously proposed concept for the achievem ent of high glass-forming ability for multicomponent amorphous alloys.