Viscous flow behavior and thermal properties of bulk amorphous Mg₅₈Cu₃₁Y₁₁ alloy

The viscous flow behavior of the Mg₅₈Cu₃₁Y₁₁ bulk amorphous rods in the supercooled viscous region is investigated using differential scanning calorimetry (DSC) and thermomechanical analyzer (TMA). Below the glass transition temperature, T_g, a linear thermal expansion coefficient of 3 ± 1 × 10^-6 m/m K was obtained. In contrast, significant viscous deformation occurred as a result of a compressive load above T_g. The onset, steady state, and finish temperatures for viscous flow, determined by TMA, are slightly different from the glass transition and crystallization temperatures measured by DSC. The appropriate working temperature for microforming as determined by the steady state viscous flow temperature is about 460-474 K. The effective viscosity within this temperature range is estimated to be about 10⁷-10⁹ Pa s, and it increases with increasing applied stress. The onset, steady state, and finish temperatures all decrease with increasing applied stress, suggesting accelerated crystallization in the present Mg₅₈Cu₃₁Y₁₁ under stress.