Study On High Temperature Mechanical Properties Of Primary Crystallized Zr₅₀Ni₂₇Nb₁₈Co₅ Amorphous Alloys

In recent years,amorphous alloys have been widely studied and rapidly developed because of their high hardness,high strength,corrosion resistance and other excellent properties.However,it is found that Al based,Fe based and Zr based amorphous alloys have little plastic deformation at room temperature,which obviously limits the application of amorphous alloys.The team's previous research results showed that there was obvious strain strengthening phenomenon in the study of high temperature deformation of primary crystallization Al based and Fe based amorphous alloys,and it was initially suspected that the strain strengthening phenomenon was related to the type of amorphous alloy that the amorphous alloy belongs to the primary crystallization type,that is,the precipitated primary phase?particles and the dynamic crystallization in the deformation process.However,this kind of generality has not been studied.Therefore,the research object of this paper selects the Zr based amorphous alloy with the composition of primary crystallization Zr₅₀Ni₂₇Nb₁₈Co₅,and uses the vacuum melting furnace to prepare the master alloy ingot,and uses the single roll melt quenching method to prepare the strip sample.By changing the experimental strip,setting different tensile temperature and initial strain rate to investigate the high temperature of the amorphous alloy strip.The high temperature deformation and fracture morphology of the tensile strip samples were studied by the structural characterization and micro morphology observation.The high temperature tensile test results of Zr₅₀Ni₂₇Nb₁₈Co₅ amorphous alloy show that the strain rate of the sample is 1×10-4 s-1,the high temperature tensile stress-strain curves at420?,430?,440?,500?and 510?respectively show strain strengthening phenomenon;when the experimental temperature is fixed,the lower the strain rate is,the easier strain strengthening phenomenon will occur;when the strain rate is fixed,the higher the experimental temperature is,the lower the tensile strength and yield strength of the sample strip.In addition,the enthalpy values of the deformed and undeformed parts of the same strip under the same conditions are obtained by DSC,and then compared with the enthalpy values of the amorphous alloy strip under the initial state,it can be concluded that the enthalpy values of the deformed parts are greater than the enthalpy values of the undeformed parts,so it can be known that the deformation is conducive to the precipitation of the crystalline phase.Under the same loading condition,the amorphous alloy strips were stretched at high temperature after being filled with argon.The experimental results show that the strain strengthening phenomenon exists at 440?and 520?,and the tensile strength,yield strength and strain of the strip samples are generally better than that of the strip samples without argon condition.The fracture morphology obtained under different temperature and strain rate is also different.In the fracture morphology,there are not only vein pattern but also river pattern.The vein pattern with clear texture and dense fine grain or river pattern corresponds to high plastic deformation ability.