Annealing-induced enthalpy relaxation behavior of Ni-Pd-P-B bulk glassy type alloys

Annealing-induced structural relaxation behavior of Ni₆₀Pd₂₀P₁₆B₄ and Ni₄₀Pd₄₀P₁₆B₄ bulk glassy type alloys with maximum diameters above 10 mm was examined by measuring the temperature dependence of apparent specific heats in the as-spun and annealed states. The enthalpy relaxation (ER) occurs through a single stage. No distinct ER peak with a maximum phenomenon is observed at lower annealing temperatures (T_a) below about 523 (~T_g −65) K, while a significant ER peak is recognized after annealing near glass transition temperature (T_g). No ER peak phenomenon as a function of T_a in the T_a range up to T_g −65 K is due to the high stability to atomic rearrangement during annealing. The annealing-induced ER is independent of composition ratio of Ni/Pd and concluded to be a feature for multicomponent bulk glassy type alloys. The single stage ER behavior as a function of T_a is the same as that for typical bulk glass-type alloys in Zr-, La- and Pd-based systems. This ER behavior is different from the appearance of distinct two ER peaks for multicomponent amorphous alloys without glass transition. The same ER behavior over the wide Ni/Pd ratios for the present alloys provides an essential knowledge on the structural stability of bulk glassy type alloys.