Formation ability, thermal stability, and mechanical properties of the Zr50Cu34Al8Ag8 amorphous alloys prepared by different mold materials

Abstract

In the present study, Zr50Cu34Al8Ag8 amorphous alloy rods with a diameter of 3 mm were prepared and the influence of the cooling capacity on the properties of cast samples was analyzed. To this end, three mold materials, including heat-resistant steel, copper, and high purity graphite were utilized. Then the amorphous structure, glass-forming ability, and thermal stability of the cast alloy were investigated using an X-ray diffractometer and differential scanning calorimeter. A universal testing machine was applied to investigate the mechanical properties of amorphous alloys with different mold materials. The fracture characteristics of the amorphous alloy were analyzed by scanning electron microscope, and the microstructures were analyzed using a high-resolution transmission electron microscope. The experimental results showed that among the studied cases, the highest glass-forming ability was achieved from the copper mold. Moreover, the glass transition and crystallization activation energies of the amorphous alloy obtained by suction casting of high-purity graphite mold were the largest, which were 525.8 kJ/mol and 334.0 kJ/mol, respectively, reflecting good thermal stability. Meanwhile, the performed analyses revealed that the fracture strength of the amorphous alloy and the corresponding strain were 1888.2 MPa and 3.55%, respectively, indicating that the cast sample has good mechanical properties. With the decrease of the cooling rate, the content of free volume in the amorphous alloy of high-purity graphite mold suction casting decreased, and the ordered structure was generated, which was the main reason for its high thermal stability and plastic deformation ability.