Dynamical mechanical analysis of metallic glass with and without miscibility gap

The dynamic mechanical properties of the miscible Cu50Zr50 and immiscible Cu50Ag50 amorphous materials are investigated to explore the relationship between deformation mechanism and relaxation of glass through molecular dynamics simulation with modified embedded atom method (MEAM). It is found that the mechanical hysteresis of Cu50Ag50 glass is more pronounced than that of Cu50Zr50 glass. The storage modulus decreases with increasing loading period or amplitude; while the loss modulus increases till the maximum, corresponding to the beginning of α− relaxation. The β− relaxation in both Cu50Zr50 and Cu50Ag50 glass shows excess tails in the loss modulus curves. However, the peak height on the left part in the curve of loss modulus as a function of temperature for Cu50Ag50 glass is higher than that for Cu50Zr50 system, which indicates that β− relaxation in Cu50Ag50 glass is more likely to be activated than that in Cu50Zr50 system due to lower number of icosahedra-like clusters. The primary α− relaxation always takes place when the most probable atomic displacement reaches a critical fraction (～23%) for Cu50Zr50 and (～21%) for Cu50Ag50 of the average interatomic distance, irrespective of whether the relaxation is induced by temperature (linear response) or by mechanical strain (nonlinear). The fast atom is defined by the atom motion displacement to explore the dynamical heterogeneity of the glass. We find that the internal fraction shows linear with the number of fast atom.