Structural relaxation of Ti40Zr25Ni8Cu9Be18 bulk metallic glass

The enthalpy relaxation behavior of Ti40Zr25Ni8Cu9Be18 bulk metallic glass follows the general characteristics of that for amorphous materials although its unique quenched-in nuclei/amorphous matrix structure: the annealing time dependence of recovery enthalpy follows a stretched exponential function with the mean relaxation time obeying an Arrhenius law, which may be due to the longer incubation time for crystallization τinc than the relaxation time τ leading to the enthalpy relaxation almost not being disturbed by the crystallization of quenched-in nuclei. The equilibrium recovery enthalpy eq T H Δ , mean relaxation time τ and stretching exponent β are all dependent on the annealing temperature, and the higher the annealing temperature, the lower the values of eq T H Δ , τ and higher of β. Two parameters, βg and τg, representing the stretching exponent and the mean structural relaxation time at the calorimetric glass transition temperature, respectively, are correlated with glass forming ability and thermal stability, respectively. The high value of βg for Ti40Zr25Ni8Cu9Be18 BMG that is much higher than 0.84 and approaches unity reveals its good glass forming ability; however, its low value of τg indicates a worse thermal stability compared with typical BMGs.