Research On Forming Process Of Zr-based Metallic Glass Micro-shaft By Micro Cross Wedge Rolling

With the increasing development of micro electro mechanical system,aerospace and biomedicine,micro-shaft parts are becoming more and more popular.As a typical supporting component,the micro-shaft is subjected to complex alternating loads.Its manufacturing strength,precision and efficiency determine the application prospects of the entire micro electro mechanical system.Metallic glass has a long-range disorder and short-range order structure,which makes it have great application potential in mechanics,physics and chemistry.There is no"grain size effect"inside and the small coefficient of thermal expansion also enables it to fully ensure product accuracy in thermoplastic forming.It is an ideal material for manufacturing micro-shaft.At the same time,plate-type micro cross wedge rolling has the advantages of high efficiency,high material utilization rate and a wide variety of products.Based on this,according to the superplastic deformation ability of metallic glass in the subcooled liquid phase region and the one-time forming characteristics of plate micro cross wedge rolling,a thermoplastic micro cross wedge rolling for metallic glass is proposed.Firstly,the microstructure,thermal properties and superplastic deformation properties of Zr₃₅Ti₃₀Be_26.75Cu_8.25 metallic glass are investigated by X-ray diffraction analysis,differential scanning calorimetry and Gleeble3800 thermal simulation machine.In the high temperature section of the supercooled liquid region and high strain rate,the effects of temperature,strain rate and sample size on the rheological behavior are studied.Based on the Maxwell-Pulse model,the constitutive model of metallic glass suitable for micro cross wedge rolling is established by introducing four dimension factors.The accuracy of the model is verified by comparing the displacement-load curves of experiment and simulation.Secondly,the die of micro cross wedge rolling is optimized and designed,and different distribution types linear surface texture is designed on the side of the die wedge to drive the rolling piece to rotate stably and ensure the forming accuracy.The influence rule of micro cross wedge rolling process parameter on the forming quality of micro-shaft is obtained by orthogonal test.Taking the dimensional tolerance and the maximum principal stress as the constraint conditions,the micro cross wedge rolling thermoplastic forming map of Zr-based metallic glass micro-shaft is constructed,aiming at different section shrinkage rate.Finally,the variation characteristics of the metal flow,stress field,strain field and temperature field of the Zr₃₅Ti₃₀Be_26.75Cu_8.25 metallic glass formed by plate-type micro cross wedge rolling are analyzed,and the deformation mechanism of the micro-shaft is expounded.The influence of the heating rate on the microstructure and mechanical properties of the sample during the forming process of micro cross wedge rolling is studied.It is revealed that the micro-heating phenomenon in the deformation process can promote the transformation of the amorphous matrix to the crystalline structure,but does not cause obvious the crystallization of the metallic glass under the condition of controlling deformation parameters,which provides a basis for the following experiments of micro cross wedge rolling.