Grain growth kinetics in a supercooled liquid region of Zr65Cu27.5Al7.5 and Zr65Cu35 metallic glasses

The grain growth kinetics of a Zr₂Cu crystalline phase in a supercooled liquid region of Zr₆₅Cu_27.5Al_7.5 and Zr₆₅Cu₃₅ metallic glasses was examined at different temperatures. Since no significant changes in the constitution and strain in Zr₂Cu phase were seen for the annealed samples, the grain size calculated from a half value width of the X-ray diffraction peak by Scherrer's formula was used. The grain growth is controlled by a single kinetics with a thermal activation process of Arrhenius type, which is described byThe activation energy for the grain growth of Zr₂Cu is 165 ± 10 kJ mol^–1 for Zr₆₅Cu_27.5Al_7.5 and 440 ± 30 kJ mol^–1 for Zr₆₅Cu₃₅. The lower activation energy in the ternary glass is attributed to the mechanism of which the crystallization and grain growth are dominated by redistribution of only Al, while the much higher activation energy might reflect the difficulty of the diffusion of Zr with larger atomic size in the binary glass. It is concluded that the difference in the grain growth mechanism is an important factor of stabilizing the glassy state.