Structural Relaxation of La55Al25Ni10Cu10 Bulk Metallic Glass

The relaxation process and glass transition kinetics of the La55Al25Ni10Cu10 bulk metallic glass (BMG) below the calorimetric glass transition were investigated by differential scanning calorimetry. Enthalpy relaxation was observed in isothermal annealing experiments below the glass transition temperature Tg. The time-dependent enthalpy relaxations were well described by a stretched exponential relaxation function, with an exponential index 0.78. An apparent activation energy E = 60.8 kJ/mol was derived from the temperature dependence of the relaxation time. The equilibrium free volume concentration at a temperature about 30 K below Tg is 10−17 to 10−13, calculated using an empirical Vogel–Fulcher–Tammann (VFT) type equation.