Formation and Decomposition of Clustered Glass Phase in Zr60Al10Co22Ag8 Amorphous Alloy with High Thermal Stability
An amorphous alloy Zr6oAl10Co22Ag8 with high thermal stability was designed by introducing Co-Ag atom pair with positive mixing enthalpy and large atomic size difference and reducing Zr content.The as-spun amorphous alloy ribbons were prepared by vacuum single-roller melt-spinning method.The as-spun amorphous alloy ribbons were annealed at different temperatures.The structural characteristics and crystallization behavior of the as-spun amorphous alloy ribbons were studied by X-ray diffractometer(XRD),differential scanning calorimeter(DSC),and transmission electron microscope(TEM).The formation of clustered glass phase in Zr6oAl10Co22Ag8 amorphous alloy and its effect on the thermal stability of the alloy were discussed.The results show that a fully amorphous phase(am)is formed in Zr6oAl10Co22Ag8 as-spun alloy ribbons,and there are two exothermic peaks during heating.Clustered glass phase(C-glass)is formed after annealing at the temperature just above Tx1.Even being heated for up to 24 h,the alloy ribbons still exhibit atomic disordered structure.The crystallization behavior is as follows:[am]→[C-glass]→[C-glass'+Al2CoZr6+AgZr+Ag2Al]→[Al2CoZr6+AgZr+AlZr3](where C-glass'is the crystalline residual clustered glass phase).The existence of a large number of Co-Ag atom pairs with positive mixing enthalpy and large atomic size difference leads to the difficulty of long range rearrangement of constituent elements,which induces the extremely high resistance to crystallization of clustered glass phase.This kind of amorphous alloys,which can produce clustered glass phase and resist crystallization under wide annealing conditions,provide a new design method for new heat-resistant amorphous alloy.