Effect Of Temperature And Strain Rate On High Temperature Mechanical Properties Of Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 Amorphous Alloy

Zr-based amorphous alloys have the properties of high fracture strength,high hardness and superplasticity in the supercooled liquid phase region.However,brittle fracture along a single shear zone extension occurs in Zr-based amorphous alloys at room temperature with little plastic deformation,which severely limits the wide application of amorphous alloys in the field of engineering materials.After research,it has been found that Fe-based amorphous alloys and Al-based amorphous alloys with primary crystalline exhibit obvious strain hardening during high-temperature tensile.As an important part of the amorphous bulk amorphous alloy system,the mechanism of high-temperature deformation of Zr-based amorphous alloys and whether strain hardening occurs during the high-temperature stretching process need to be studied and improved.Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5（Vit1）is by far the best amorphous alloy composition,and the bulk amorphous composition has been successfully used in the field of transformers and sporting goods.Therefore,Vit1 amorphous alloy with the crystallization type of primary crystallization was selected as the object of study,and Vit1 strip samples were prepared by single-roll melt rapid cooling and strip dumping method.The high-temperature deformation behavior of Vit1 strip samples was studied by varying the temperature and initial strain rate,and the fracture morphology of Vit1 samples after tensile fracture was investigated to investigate the microscopic fracture mechanism under different conditions.For Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 amorphous alloy at high temperature tensile testing,the results show that the sample exhibited a significant strain hardening phenomenon at the end of the high temperature tensile stress-strain curve from 370°C to 400°C at a strain rate of 2×10^-4s^-1,and the higher the tensile temperature the more obvious the phenomenon was.The stress-strain curves from 350°C to 380℃also show stress overshoot behavior,and the overshoot stress decreases as the stretching temperature increases.The enthalpy values of the deformed and undeformed regions of the amorphous alloy strips were measured by DSC,and the difference in crystal volume fraction between the deformed and undeformed regions was calculated to be 3%,which indicates that the deformation is conducive to crystallization and is one of the reasons for the strain hardening phenomenon;the fracture morphology at room temperature is vein-like,and the fracture surface undergoes a lot of plastic deformation at high temperature deformation,showing better plasticity.The strain rate of Vit1 amorphous alloy at 380℃was in the range of5×10^-4 s^-1 to 1×10^-3 s^-1.With the increase of the initial strain rate leading to the generation of free volume,the aggregation of free volume caused the softening of the amorphous alloy,and the tensile strength of Vit1 amorphous alloy showed an increasing trend with the increase of the initial strain rate.The effects of temperature and initial strain rate on the superplastic properties of Vit1 amorphous alloy were combined,and the most suitable superplastic extrusion forming conditions were obtained at 380℃and 1×10^-3 s^-1 for temperature and strain rate parameters.