超细晶纯铝微挤压变形行为与微观组织演变规律研究

发布时间：2018-03-09 10:05

  本文选题：微挤压　切入点：微成形　出处：《哈尔滨工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：微系统技术和微机电系统,在近期快速发展并逐步投入到实际应用当中,微型零件在应用中更加受重视。微型热交换器、微型反应器、微型电机、光学传感器等微机电系统的重要零件,在微机电系统中的微结构的制造技术成为广大科研工作者的关注重点,超精密机械加工、LIGA、刻蚀等微器件制造技术在可加工材料种类、成本、加工效率方面存在不同程度的进步空间。塑性微挤压具有着重复性好、成形件机械性能优异、成本低、效率高、工艺简单等特点,因此研究微挤压技术有着充足的必要性。本课题利用等通道转角挤压法制备微挤压实验原始坯料,并通过显微硬度测量和电子背散射衍射显微观察研究材料组织性能,发现晶粒的细化是主要通过发生在凹模内拐角处的剪切变形使材料内部形成小角晶界、大角晶界。对实验坯料进行压缩实验发现与粗晶相比超细晶材料对压缩速率更为敏感,同时其成形精度更高。基于有限元数值分析模拟软件DEFORM-3D10.2对微挤压过程进行三维数值模拟,发现随着凹模锥角越来越大,挤压力越来越大,锥角区域塑性流动越来越差;另外对微挤压过程应力应变速度场进行分析,发现应力在锥角区域集中,在已变形区外端应变值较大,坯料上部的速度值是大于坯料下部速度值的。通过进行微挤压实验,介绍了实验模具和实验设备在实验中作用,研究了不同坯料几何尺寸、不同坯料晶粒情况、不同挤压速度对实验结果的影响并分析,发现当坯料直径减小时,单位挤压力曲线下降,当坯料直径减小到1mm时,出现了单位挤压力上升的尺度效应现象,并给予了合理解释。在对微挤压件的电子背散射衍射显微组织分析中发现,挤压件可被划分为未变形区、变形区、已变形区,挤压件接近锥角部分晶粒变形剧烈,晶粒尺寸和模具尺寸之比越大则变形协调性越差的规律,连续挤压棒料在热处理温度300℃以上时其热稳定性下降。
[Abstract]:Micro-system technology and micro-electromechanical system, in the recent rapid development and gradually put into practical applications, micro-parts in the application of more attention to micro-heat exchangers, micro-reactors, micro-motor, The important parts of MEMS, such as optical sensors, have become the focus of scientific research. The manufacturing technology of micro-structure in MEMS has become the focus of scientific research. The manufacturing technology of micro-devices such as ultra-precision machining, etching and so on, is in the category of machinable materials. The plastic micro-extrusion has the advantages of good repeatability, excellent mechanical properties, low cost, high efficiency, simple process and so on. Therefore, it is necessary to study the micro-extrusion technology. In this paper, the raw blank of micro-extrusion experiment is prepared by equal channel angular extrusion method, and the microstructure and properties of the material are studied by microhardness measurement and electron backscatter diffraction microscopy. It is found that the grain refinement is mainly caused by shearing deformation at the corner of the die to form the small angle grain boundary and the large angle grain boundary. The compression experiment of the experimental blank shows that the ultrafine grain material is more sensitive to the compression rate than the coarse grain material. At the same time, the forming accuracy is higher. Based on the finite element numerical analysis software DEFORM-3D10.2, the three-dimensional numerical simulation of micro-extrusion process is carried out. It is found that with the increasing conical angle of the die, the extrusion force is increasing, and the plastic flow in the cone-angle region is getting worse and worse. In addition, the stress-strain velocity field of micro-extrusion process is analyzed. It is found that the stress is concentrated in the cone angle region, and the strain value is large at the outside end of the deformed area, and the velocity value of the upper part of the blank is larger than the velocity value of the lower part of the blank. This paper introduces the function of experimental die and experimental equipment in the experiment, studies the influence of different blank geometry size, different blank grain condition and different extrusion speed on the experimental results, and finds out that when the blank diameter is reduced, The unit extrusion pressure curve decreases, when the blank diameter decreases to 1 mm, the scale effect of unit extrusion pressure rise appears, and the reasonable explanation is given. The extrusion part can be divided into undeformed zone, deformed zone, deformed zone, and the deformation of the part of the extruded part near the cone angle is severe. The bigger the ratio of grain size to die size is, the worse the compatibility of deformation is. The thermal stability of the continuous extrusion bar decreases when the heat treatment temperature is above 300 鈩，

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