Effect of icosahedral clusters on β-relaxations in metallic glasses

The most pronounced β-relaxation was found in the Y-based binary metallic glasses (MGs). The correlation between β-relaxation and local atomic structure was studied. The dynamic mechanical measurements were performed for three chosen binary systems: Zr-, Ti-, and Y-based MGs. The experimental results show that, in each systemthe larger negative enthalpy of mixing ($\Delta H_m)$ between the component elements makes β-relaxation become more pronounced. The less negative value of $\Delta H_m$ facilitates the formation of icosahedral clusters, which have a pinning effect on the excitation of β-relaxations and correspondingly make the β-relaxation become less pronounced. These chemical effects on β-relaxations can only be compared in the same MG system, and it is not suitable for the comparison between different systems due to the different features of the major metallic elements. (paper)