The limited annealing treatment of the Zr₅₅Cu₃₀Al₁₀Ni₅ metallic glass below its glass transition temperature

Annealing treatment below the glass transition temperature of Zr₅₅Cu₃₀Al₁₀Ni₅ bulk metallic glass (BMG) specimens are investigated. Every 10 K temperature interval isothermal limited annealing treatment time will be selected to draw up time-temperature-transformation (T-T-T) curve. The apparent activation energy of crystallization is about 325 ± 7 kJ/mol, higher than the values of supercooled liquid region conditions. Surface hardness of the samples before and after the limited annealing treatment are tested by nanoindentation, where the spherical-like crystallization morphology indicate the higher standard deviation of surface hardness of the BMG after the limited annealing treatment. The crystallization kinetics of the Avrami exponent is 4 in accordance with spherical-like crystallization morphology. A short review on mathematical setting of the problem could distinctly give the differences of the different crystallization behaviors at different temperature regions. Avrami exponent is from 4 to 3, explaining the crystallization morphology is from spherical-like to dendritic, could be ascribed to the concepts of symmetry breaking.