A Study On The Micro-plastic Forming Mechanism Of Zr-based Amorphous Alloys Under High Frequency Vibration Load

The amorphous alloy has excellent mechanical properties and electromagnetic properties,comparing with the same or similar crystalline alloys.In the supercooled liquid region,it shows a viscous fluid feature,which has a good micro-forming ability.At room temperature,the macroscopic plastic deformation of most amorphous alloys is very limited due to the absence of dislocation and twin defects.At present,it is mainly used to optimize the two experimental parameters of the deformation temperature and time to study the method of improving the forming ability of amorphous alloy.Because the temperature and forming time are two mutually limiting factors,the higher temperature makes the time period of crystallization incubation smaller,which brings the risk of amorphous gold crystallization.However,vibration field can reduce the viscosity of non-newtonian fluid,thus improving the ability of deformation and fluid filling mold.Amorphous alloys exhibit non-Newtonian fluid properties at appropriate temperature and shear rates.Therefore,this paper designed a research scheme of composite extrusion micro-forming under high frequency vibration field with Zr₅₅Cu₃₀Al₁₀Ni₅ bulk amorphous alloy as the research object,and found out the forming mode and mechanism of amorphous alloy under high frequency vibration field.The project first prepared Zr₅₅Cu₃₀Al₁₀Ni₅ bulk amorphous alloy by copper mould technique.Through XRD,detected the structural components which was determined on its structural components,and the sample was determined as amorphous state,and using DSC curves determined that the experimental forming temperature was 447^oC.According to self-positioning and overall mold handling principles,the composite extrusion micro-mould was designed and manufactured.Using Deform-2D software analyzes the composite extrusion micro-forming process of Zr₅₅Cu₃₀Al₁₀Ni₅ bulk amorphous alloy in the supercooled liquid region.It analyzed the speed and stress distribution field under micro-forming process,and the influence of different die size on micro-forming.It was found that the stress and rheological rate of the blank were very uneven in the process of composite extrusion,and the deformation resistance of materials increased with the increase of the punch size.Using ultrasonic vibration device,set the extrusion rate of compressive bar on 0.02 mm/s,choose different frequencies?18 kHz²1 k Hz?and vibration power?50%⁹5%?.Through cross experiment plan,completed the experiment on the Zwick material test machine.And the time of experimental operation was less than 7 min.According to the forming load time curve,it was found that high frequency vibration could improve the rheological forming ability of amorphous alloy,and the effect was obvious when the frequency was 21kHz.The rheological mechanics and the mechanism of vibration loading of amorphous alloy in the super-cooled liquid region under vibrational field action were analyzed,and found that because of the cyclic contact between the blank and the platen platform,the vibration load reduced.Through contrast analysis of different punch sizes?1.2mm,1.5mm and 1.8mm?,it was found that the parts formed difficultly in large size punch,which could easily lead to damage mould.Basing on the simulation analysis of the stress changes in the forming process,it was found that the flow characteristics of amorphous alloy in the supercooled liquid region were gradually shifted from Newtonian to Non-newtonian fluid with the increase of strain rate.Using SEM observed the appearance size of the forming sample and microstructure after experiment,and determined its amorphous structure.Using the hardness to test its mechanical changes,found that the high frequency vibration caused the change of the properties of amorphous alloy,which led to the hardness of the deformation parts improvedIn this paper,high frequency vibration loading was applied to high temperature micro-forming and the theory of vibration used to reduce the viscosity was applied to the micro-forming of amorphous alloy,which proposed a new method for improving the micro-forming ability of amorphous alloys.