超细晶纯铜T型微镦挤变形行为及微观组织演变

发布时间：2018-04-24 03:38

  本文选题：等径角挤压 + 超细晶纯铜　； 参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：微系统技术以及微机电系统的迅速崛起,带动当前工业朝着小型化、微型化的方向发展。而利用传统工业材料生产微型零件时,由于晶粒尺寸与微型零件的某一维度尺寸相当,出现明显的尺寸效应,从而在实际生产中影响成形件最终的尺寸精度,提高生产成本,且降低了生产效率。研究表明,利用超细晶材料生产微型零件时,上述缺点可得到明显改善,极大的提高了生产效率和产品质量,为微成形技术的发展铺平了道路。与传统的压缩实验相比,T型微镦挤实验具有模具结构简单、操作方便等优势,金属内部同时进行挤压变形和压缩变形,材料内部变形剧烈,且可利用同一组模具对不同尺寸的试样进行实验。因此,本文首先利用等径角挤压工艺制备超细晶纯铜材料,利用Deform-3D有限元分析软件模拟T型微镦挤变形行为,并在室温及高温条件下对超细晶纯铜进行T型微镦挤实验,分析在热力场耦合作用下超细晶纯铜微观组织演变规律。在T型微镦挤变形过程中,根据金属材料的流动规律,可将变形分成两个阶段:第一阶段,试样向凹模型腔内部的流动速度大于向凹模两侧的流动速度,此时材料以挤压变形为主,压缩变形为辅;第二阶段,试样向凹模两侧测流动速度大于向型腔内部的流动速度,此时材料以压缩变形为主,挤压变形为辅。通过有限元分析及实验结果表明:凹模型腔参数对T型微镦挤变形时的变形力、挤压筋高度及高宽比λ有显著影响,凹模表面粗糙度对变形第一阶段的变形力影响不大,但在变形的第二阶段,变形力随表面粗糙度的增加而增大;凹模圆角半径和开口角度对整个T型微镦挤变形中的变形力都有显著影响,随着凹模圆角半径和开口角度的增加而变大;挤压筋高度及高宽比λ随凹模表面粗糙度、圆角半径及开口角度的增大而线性降低。随着变形温度的升高,由于变形时超细晶纯铜发生动态回复和动态再结晶,变形力逐渐下降;当变形温度低于200℃时,超细晶纯铜内部发生动态回复,变形力和高宽比缓慢降低,但是挤压筋高度缓慢增大,晶粒长大不明显;当变形温度高于250℃时,变形力迅速降低,挤压筋高度和高宽比λ迅速增大,晶粒长大明显,当变形温度达到400℃时,平均晶粒尺寸由0.44μm长大到3.4μm。
[Abstract]:The rapid rise of micro system technology and microelectromechanical system has led to the development of miniaturization and miniaturization in the current industry. While using traditional industrial materials to produce micro parts, the size of grain size corresponds to a dimension size of the micro parts, which has obvious size effect, which affects the final parts in actual production. The size accuracy improves the production cost and reduces the production efficiency. The research shows that the above shortcomings can be improved obviously, greatly improving the production efficiency and product quality, and paved the way for the development of micro forming technology. Compared with the traditional compression experiment, the T micro upsetting experiment has a mold. The structure is simple, the operation is convenient and so on. The internal deformation and compression deformation of the metal are simultaneously carried out. The internal deformation of the material is intense, and the same group of dies can be used to test the samples of different sizes. Therefore, first of all, the superfine crystal pure copper material is prepared by the equal diameter angle extrusion process, and the Deform-3D finite element analysis software is used to simulate the T microfiber. The behavior of upsetting and extrusion deformation was carried out at room temperature and high temperature. The micro upsetting extrusion experiment of ultrafine crystal copper was carried out at the condition of room temperature and high temperature. The microstructure evolution law of ultrafine crystal copper under the coupling of thermal field was analyzed. In the process of T micro upsetting and extrusion, the deformation can be divided into two stages according to the flow law of metal material. The first stage, the specimen to the concave model cavity The internal flow velocity is greater than the flow velocity to the two sides of the die. At this time, the material is dominated by extrusion deformation and the compression deformation is supplemented. In the second stage, the flow velocity of the sample to the concave die is greater than that of the inner cavity. At this time, the material is mainly compressed and the extrusion deformation is supplemented. The finite element analysis and experimental results show that the die is a concave die. The parameters of the cavity have significant influence on the deformation force, the height of the extruding bar and the ratio of the height to width. The surface roughness of the die has little effect on the deformation force in the first stage of the deformation, but in the second stage of the deformation, the deformation force increases with the increase of the surface roughness; the circular corner radius and the opening angle of the die have a small upsetting and extrusion deformation of the whole T type. With the increase of the radius of the concave die and the angle of the opening, the height of the extruding bar and the ratio of the height to width are linearly decreased with the increase of the surface roughness, the radius of the circle and the angle of the opening. With the increase of deformation temperature, the dynamic recovery and dynamic recrystallization of the superfine crystal copper are formed as the deformation temperature rises. When the deformation temperature is below 200 c, the internal dynamic recovery occurs in the ultrafine crystal pure copper, the deformation force and the ratio of height to width decrease slowly, but the height of the extruding bar increases slowly and the grain growth is not obvious. When the deformation temperature is higher than 250, the deformation force decreases rapidly, the height and width ratio of the extruding rib increase rapidly, and the grain growth is obvious. When the grain grows obviously, when the grain grows, the grain grows obviously. When the grain grows, the grain grows obviously. When the grain grows, the grain grows obviously. When the grain grows, the grain grows obviously, when the grain grows, the grain grows obviously. When the shape temperature reaches 400 degrees, the average grain size grows from 0.44 m to 3.4 m..

【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG379;TG146.11
，

本文编号：1795007