Effect Of Temperature And Strain Rate On The High Temperature Mechanical Properties Of Zr-based Amorphous Alloy

Zr-based amorphous alloys have been studied extensively in recent years because of their good amorphous forming ability as well as their high strength,high hardness and excellent corrosion resistance.However,the current research on amorphous alloys is facing two main problems to be broken through.On the one hand,Zr-based amorphous alloys only exhibit macroscopic linear elastic deformation at room temperature,leading to instantaneous catastrophic brittle fracture,which severely limits their use as structural materials due to the rapid expansion of a single shear band at room temperature.On the other hand,the amorphous alloy undergoes structural transformation when the deformation temperature approaches Tg（glass transition temperature）,starting with a gradual shift from elastic deformation to plastic deformation,with viscosity and plasticity increase,but the high temperature makes the amorphous alloy soften and the strength is greatly reduced.Therefore,the high temperature mechanical properties of Zr-based amorphous alloys are of great significance for research.In the preliminary study,it was found that temperature and initial strain rate had some influence on the deformation behavior of Zr₅₁Cu₂₉Al₂₀ amorphous alloy,but the specific high temperature deformation mechanism is still not fully studied.Uniaxial tensile tests were carried out on the Zr₅₁Cu₂₉Al₂₀ amorphous ribbon samples at different temperatures and initial strain rates to investigate its high temperature deformation behavior.And the microscopic fracture behavior of the Zr₅₁Cu₂₉Al₂₀ samples was investigated by observing the fracture morphology after uniaxial tensile tests,combining with SEM,XRD and DSC tests.Uniaxial tensile experiment on Zr₅₁Cu₂₉Al₂₀ amorphous alloy ribbons shows that the specimens are highly sensitive to temperature and initial strain rate.At the initial strain rate of3.33×10^-4 s^-1,the stress-strain curves of the specimens at temperatures within the supercooled liquid region（460°C,470°C,485°C and 500°C）showed remarkable strain hardening phenomenon,the higher the temperature and the more pronounced the strain strengthening.Keeping test temperature of the Zr₅₁Cu₂₉Al₂₀ amorphous alloy uniaxial tensile,the strain hardening phenomenon of the specimen is more pronounced at relatively low initial strain rates.The fracture pattern is vein-like,but the pattern of high temperature fracture pattern is finer,more prominent and clearer,corresponding to the stress-strain curve shows better plasticity.According to the DSC enthalpy values of the deformed and non-deformed part of the amorphous alloy ribbon,the difference in crystal volume fraction between the deformed and non-deformed region is calculated to be up to 12%,thus it is known that deformation is conducive to crystallization.The strain hardening phenomenon of Zr₅₁Cu₂₉Al₂₀ amorphous alloy strips during high temperature stretching is related to the dynamic crystallization,the greater the dynamic crystallization in the amorphous,the more pronounced the strain hardening phenomenon.