Room-temperature creep and structural relaxation of Mg–Cu–Y metallic glasses

Structural relaxation of Mg–Cu–Y metallic glasses occurs at room-temperature (∼0.7 Tg) and induces an abrupt embrittlement after periods of time that depend on the relative proportions of Cu and Mg. Internal friction measurements of as-quenched samples show that Mg65Cu25Y10 is in a more relaxed state than Mg85Cu5Y10, suggesting a more compact structure for the alloy with a larger amount of Cu, which is the smallest atom in the system. Relaxation spectra, calculated from the anelastic component of nanoindentation creep curves, show that the two alloys are in a similar relaxed state, when they become brittle. The results are discussed in terms of the defects characterizing the disordered structure of the metallic glass.