Increasing the kinetic stability of bulk metallic glasses

TitleIncreasing the kinetic stability of bulk metallic glasses
Publication TypeJournal Article
Year of Publication2016
AuthorsWang, J.Q., Y. Shen, J.H. Perepezko, and M.D. Ediger
JournalActa Materialia
Start Page25
Date Published12/2015

Metallic glasses are non-equilibrium materials and the glass transition temperature upon heating Tg,h can be used to characterize the kinetic stability of the glass. Annealing below the glass transition is well-known to induce relaxation processes that reduce the glass enthalpy. We demonstrate that a liquid-cooled Au-based metallic glass can achieve very high kinetic stability by an optimal annealing treatment to yield a large increase in Tg,h of 28 K; this is 3–5 times larger than the increase usually reported. The measured enthalpy decrease of 1100 J/mol is about 50% of the difference between the as-cooled glass and the equilibrium crystalline state and reaches the extrapolated enthalpy of the supercooled liquid. The optimal annealing conditions can be determined by an enthalpy-temperature-time (ETT) diagram which is proposed for the first time based on the comprehensive examination of relaxation processes. At equilibrium, a direct relation is established between the increase in kinetic stability as measured by the increase in Tghand the enthalpy decrease.