Crystallization and embrittlement behavior of a Zr55Al10Ni5Cu30 metallic glass having different Si and O contents

Metallic glasses as non-equilibrium materials crystallize at a critical temperature, accompanying their embrittlement. The size of glassy alloys is dependent on their glass-forming ability. The development of an appropriate Joining technique is important for the extension of industrial applications. In the present study, we examine crystallization behavior of Zr55Al5Ni5Cu30 glassy alloy upon annealing. In the beginning of the crystallization process, a clustering, a crystal nucleation and the crystal growth processes take place sequentially. The phase transition behavior was examined by differential scanning calorimetry (DSC). The kinetics of the crystallization process can be analyzed by the changes in the volume fraction of the crystalline phase which scales with the exothermic heat release and density measurement. The crystallization process in the Zr55Al10Ni5Cu30 alloy is found to be diffusion-control led. The values of the Avrami exponent are between 2.3 and 2.8. Therefore, the velocity of nucleation and crystallization processes should scale with the diffusion velocity of the constituent elements in the metallic glass. The diffusion rate can be estimated using the diffusion coefficients of the constituent elements, as a function of time and temperature. The slope of the calculated iso-precipitation line of CuZr2 phase on the fixed TTT diagram is well fitted with the lines representing ductile and brittle behavior of the sample. The results indicate that the most harmful crystalline phase, which causes embrittlement is CuZr2. The influence of Si contamination on the crystallization behavior is also studied in the present work.