Relaxation kinetics of bulk metallic glasses below glass transition temperature

The free volume relaxation just under the glass transition region was investigated by the high-resolution density measurement using the bulk metallic glasses with the compositions of Pd₄₀Ni₄₀P₂₀ and Zr₅₅Cu₃₀Ni₅Al₁₀. The relaxation process was well described by a stretched exponential function with Kohlrausch exponent values less than unity. The reduced free volumes in an as-quenched state were estimated as 0.0117 and 0.0353 for Pd₄₀Ni ₄₀P₂₀ glass and Zr₅₅Cu₃₀Ni ₅Al₁₀ glass, respectively. The specific heat curves C _P(T) for Pd_42.5Cu₃₀Ni_7.5P ₂₀ alloy were obtained for the supercooled liquid, the equilibrium liquid and the crystallized alloy. The isenthalpic Kauzmann temperature T _KH and isentropic Kauzmann temperature T_KS were estimated as 471 K and 522 K, respectively, from the specific heat data.