Thermal Crystallization and Electron Irradiation Induced Phase Transformation Behavior in Zr_66.7Cu_33.3 Metallic Glass

Abstract

Phase transformation behavior and phase stability of Zr_66.7Cu_33.3 metallic glass were examined during thermal annealing and electron irradiation. Metastable f.c.c.-Zr₂Cu phase precipitated in amorphous matrix and formed nanostructure by electron irradiation induced crystallization. With further thermal annealing, the nano grains of the f.c.c.-Zr₂Cu coarsened accompanied by precipitation of thermally stable b.c.t.-Zr₂Cu phase from amorphous matrix. The thermal equilibrium b.c.t.-Zr₂Cu crystalline phase was transformed to the nanocrystalline f.c.c.-Zr₂Cu phase through the amorphous state during electron irradiation. The unique solid state amorphization and crystallization behavior by electron irradiation can be explained by the thermodynamical model based on the change in relative phase stability among amorphous and crystalline phases by electron irradiation. The thermal stability of the f.c.c.-Zr₂Cu phase and the effect of dose rate on electron irradiation induced phase transformation were investigated in order to confirm the validity of the thermodynamical model.