Ultrasonic Assisted ECAP Preparation Technology And Properties Of Ultra-fine Grain Evaluation

Micro parts play a great important role in micro-electromechanical systems(MEMS), and has been widely applied in all aspects of social life, such as biomedical, electronic communications and aerospace, etc. In turn, the high demand and wide use of micro plastic parts requires its raw materials to low-cost, low energy, high efficiency, high-performance. Therefore, the producing of the material attracts extensive attentions.Ultra-fine grain materials is one of the most important study, by design and control the microstructure of the material to inspire the potential performance of existing materials, even made of new materials. Metal material is composed of a large number of grain, grain boundary and internal interface, these grains connected by the interface, grain boundary, are all different in size, shape and orientation. The performance of metal material largely depends on the performance of each single one, interface or the characteristics of the statistical distribution of both. Ultra-fine crystal material has good physical properties and mechanical properties for its structural characteristics. Whether the actual preparation of ultra-fine crystal material has excellent performance consistented with theoretical, be focused by many scholars.ECAP(Equal Channel Angular Pressing) is a kind of effective method of plastic processing, which can make the material grain size from the micron grade down to nanoscale without changing the cross-sectional area of the material and geometry shape by producing homogeneous severe plastic deformation. Now, the ECAP technology is used in aluminium and its alloy, copper and its alloy, iron, mild steel and other materials with good effect of significantly enhance the performance. Since the 1960 s, ultrasonic assisted metal plasticity processing was applied in metal forming. However, the ultrasonic vibration to the assiste ECAP has not been reported until now. Based on the research of ultrasonic vibration on polymer powder forming and the learning of the copper, this study proposed the UV-ECAP(Ultrasonic Vibration Assisted- Equal Channel Angular Pressing). Processing of pure copper with ultrasonic vibration of ECAP to get ultra-fine crystal copper, surveying the material mechanical properties and microstructure evolution, explore the high frequency of ultrasonic vibration on the influence of the copper material of ECAP.Making a lot of ultra-fine crystal copper by UV-ECAP and conventional ECAP processing technology and testing them, which is verified on the ascension to performance of the copper, with high research value and development prospects.This paper studies the main contents include:1) This study proposed UV-ECAP, a process of preparing ultrafine crystalline materials which change the traditional ECAP processing methods of the static extrusion to intermittent ultrasonic vibration extrusion. Independent design modification of a set of ultrasonic vibration equal channel angular extrusion press, can undertake ECAP or UV-ECAP processing and with which making ultra-fine crystal copper, confirms the feasibility of UV-ECAP, for industrial production provide a design scheme.2) A series of tests on the ultra-fine crystal copper. Electron Back Scattering Diffraction(EBSD) analysis show that ECAP and UV-ECAP method can produce ultra-fine crystal material. Through the contrast analysis to further understand that the UV-ECAP processing of ultra-fine grain size on the conventional ECAP increases slightly, but the large angle grain increased, means that thermal stability of material processed by UV-ECAP promote largely, also validated by differential scanning calorimeter(DSC) test. Thermal stability of ascension given a lot of space for ultra-fine crystal material follow-up treatment, this is of great significance for the UV-ECAP industrialized production.3) The mechanical tensile test of ultra-fine crystal copper show that its mechanics performance superior to the ordinary material. Comparison of the mechanical tensile test of ultra-fine crystal copper,processed by ECAP and UV-ECAP,show its no great different. That means the UV-ECAP cost low energy and get a good performance same as ECAP.