Sub-Tg annealing effect on the kinetics of glass transition and crystallization for a Ti-Zr-Be-Fe bulk metallic glass

Abstract The influence of sub- T g pre-annealing on the kinetics of glass transition and crystallization of a lightweight Ti 41 Zr 25 Be 28 Fe 6 bulk metallic glass (BMG) has been investigated by isochronal and isothermal differential scanning calorimetry tests. It was found that sub- T g annealing obviously enlarges the supercooled liquid region of Ti 41 Zr 25 Be 28 Fe 6 BMG, indicating an enhanced thermal stability. The activation energies for glass transition and crystallization of the as-cast and pre-annealed samples have been calculated and compared. The pre-annealed samples possess smaller values of fragility parameter and longer incubation times upon isothermal heating compared with the as-cast sample, indicating a retarded crystallization process. The isothermal crystallization kinetics of the samples with different annealed states has been investigated in terms of the Johnson-Mehl-Avrami equation and local Avrami exponent. The current study reveals a clear sub- T g annealing effect on the kinetics of glass transition and crystallization of Ti 41 Zr 25 Be 28 Fe 6 glassy alloy and the possible mechanisms have also been proposed.