Crystallization and grain growth behaviour of Zr₆₅Cu_27.5Al_7.5 metallic glass

The phase transition by crystallization and a grain growth behavior of a Zr₆₅ Cu₂₇.₅Al_7.5 metallic glass were examined as a function of isothermal annealing time at various temperatures. At the initial stage of crystallization, a metastable Zr(Al,Cu) phase is observed, in addition to a main phase of Zr₂Cu, below the annealing temperature of 730 K. The formation of Zr(Al, Cu) may be attributed to the strong chemical affinity between Al and Zr. The grain growth rate for Zr₂ Cu is extremely low comparing with that for a Zr₆₅Cu₃₅ binary metallic glass. Therefore, the strong chemical affinity between Al and Zr seems to contribute to the retardation of nucleation and grain growth of the crystalline phases. The grain growth kinetics can be described by log(dD/dt_g) = log(k/3) - 2 log D where D is the measured grain size, t_g the grain growth time and k the constant. The activation energy Q for grain growth is calculated to be 165 kJ mol^-1.