Effect of high temperature deformation on the deformation behavior and thermodynamic properties of a Zr-based bulk amorphous alloy

Abstract

Zr 55.7 Cu 22.4 Ni 7.2 Al 14.7 alloy rods with a diameter of 3 mm were prepared by copper mold suction casting. The structure, thermodynamic properties and plastic deformation behavior of the specimens before and after compression in supercooled liquid region were studied by X-ray diffractometer (XRD), differential scanning calorimeter (DSC) and uniaxial compression machine (equipped with a high-temperature oven). The range of thermal forming process parameters was also discussed. The results show that the alloys have obvious glass transition and crystallization kinetics, and the crystallization activation energies obtained by the Kissinger and Ozawa equations are 297.1 kJ/mol and 294.9 kJ/mol, respectively. The amorphous alloys exhibit stress overshoot in low temperature region at high strain rates and deformation behavior of alloy softening in high temperature region at medium to high strain rates. Meanwhile, the viscosity of the alloy remains approximately constant at 740 K and 750 K, showing Newtonian fluid characteristic. It can be concluded that the optimal thermoplastic forming process ranges from 740 K to 750 K, 5 × 10 −4 s −1 to 5 × 10 −3 s −1 . The crystallization activation energies of the specimens after deformation are slightly higher than before, and they increase with the increase of strain rate. • Zr-based bulk amorphous alloy has a good thermodynamic stability, which facilitates thermoplastic forming. • The amorphous alloy shows superplastic deformability at high temperatures and strain rates. • The crystallization activation energies of the deformed specimens are higher than that of the undeformed. • The crystallization activation energies of the alloys after deformation increase with increasing strain rate.