Glass transition and crystallization of Ce68Al10Cu20Co2 bulk metallic glass studied by Flash DSC

In this study, glass transition and crystallization of Ce68Al10Cu20Co2 bulk metallic glass at heating rates ranging from 0.083 to 14,000 K/s, covering six orders of magnitude, are investigated. For the glass transition, two linear regions with different apparent activation energies (Ea,g) are distinguished by a critical heating rate of 2000 K/s: Ea,g decreases from 208.7 to 67.3 kJ/mol with the increase of heating rate. During the crystallization, the nucleation rate and crystal growth rate between Tg and Tm are calculated. According to their dependence on temperature, the contact angle for the nucleation of Ce crystals is estimated at 11–14 degrees. For the crystal growth, a maximum crystal growth rate of 0.03 m/s is found at 0.97 Tm. Moreover, the breakdown of the Stokes–Einstein equation in the deeply undercooled melt is observed, where the diffusivity is related to viscosity by D ∝ η−0.865.