Internal Friction Behaviors In ZrAlNiCu(Nb) BMG

Bulk metallic glasses (BMG) developed about ten years ago, known as promising engineering materials, offer new opportunities for engineering applications and the fundamental study on the nature of metallic glasses. These three dimensional metallic glasses with much higher thermal stability with respect to crystallization in the undercooled liquid state compared to conventional metallic glasses make experimental investigations of the glass transition and the undercooled liquid state of a metallic system possible that were not feasible before. This work performs the investigation of the structural transition and relaxation of Zr57Al10Ni12.4Cu15.6Nb5 and Zr65Al7.5Ni10Cu17 BMG using the internal friction technique.An internal friction (IF) peak with anomalously large magnitude which is about one order larger than that of the conventional metallic glasses is observed in the temperature dependent IF curves (Q-1-T curves). The IF peak does not change its position with the variation of frequencies, and increases in height and shifts to higher temperature with the heating rates increasing, which indicate that the IF peak exhibits the features of that of the first-order transition in crystalline solids. The position of the IF peak locates between the onset temperature of crystallization and the exothermic peak temperature corresponding to the results of DSC. The origin of the IF peak is discussed based on the crystallization mechanism.Additionally, the IF behaviors below the glass transition temperature Tg suggest anelastic and viscoelastic properties which correspond to different structural relaxations of Zr57Al10Ni12.4Cu15.6Nb5 and Zr65Al7.5Ni10Cu17 BMGBeside the behaviors of IF, DSC experiments with different heating rates were also carried out. The glass transition temperature Tg, the onset crystallization temperature Tx, and the crystallization peak temperature Tpi of the Zr57Al10Ni12.4Cu15.6Nb5 BMG are found to depend on the heating rate during the continuous heating. This phenomenon indicates that the glass transition and crystallization behave in a marked kinetic nature. At the lower heating rates, thewidth of the supercooled liquid region( â–³ T) also changes obviously with heating rate increasing, however, â–³ T doesn't increase at a higher heating rate, which demonstrates that both the glass transition and crystallization have the feature of phase transformation controlled by the thermodynamic factors. The activation energy obtained from the IF peak is equal to that obtained from exothermic peak of DSC.The present work, for the first time, investigated structural relaxation and phase transition of BMG using IF technique which proved to be a new powerful tool for studying structural relaxation and phase transition as well as GFA of BMG.