面心立方金属（Al和Ni）再结晶形核机理的三维与原位研究

发布时间：2018-03-17 17:44

本文选题：再结晶形核　切入点：柱状晶　出处：《重庆大学》2016年博士论文　论文类型：学位论文

【摘要】：形变金属退火时在变形基体中形成新的无畸变小晶粒,这一过程称为再结晶形核。工业实践表明再结晶决定了金属制品的热机械加工精细工艺和最终性能;此外,金属再结晶理论也是材料科学最基本的科学问题之一。由于金属变形组织的复杂性,以及形变组织转变为再结晶晶核后,由于形变组织的消失而引起再结晶形核证据的缺失,使得再结晶形核机理的研究十分困难。本文采用冷轧柱状晶镍和先冷轧后再打显微硬度压痕的高纯铝两种样品,研究了形变面心立方金属中的再结晶形核问题。用维氏硬度、光镜、背散射电子衍射(EBSD)、电子通道衬度(ECC)和同步辐射的差分X射线技术(DAXM)在不同维度上表征微观组织结构的变化,从而研究再结晶形核机理以及局部微观组织结构对形核的影响。在冷轧柱状晶镍的退火试验中,晶核主要在三叉晶界和晶界上形成。大部分晶核与周围变形基体的取向相近或者跟周围一个变形基体成孪晶关系。只有几个晶核具有与变形基体不一样的新取向。在三叉晶界附近的硬度测试表明:在三叉晶界处三个晶粒的硬度的差值越大,这个三叉晶界越易于形核。在冷轧并打显微硬度压痕的高纯铝样品中,压痕尖端附近显示出较复杂的晶体取向转动模式。在一系列具有不用原始取向的晶粒中,冷轧后高储层能晶粒的平均硬度值大,形核率也高。总的来说,硬度值越大的压痕形核的可能性越大。另外,在同一个晶粒不同压痕处形成的晶核的取向不是无序的,而是聚集在一定的取向空间。形变态压痕尖端附近的取向分布范围,包含了在退火中形成晶核的取向。研究进一步利用先进的基于同步辐射的DAXM,首次三维原位地表征了样品(高纯铝)内部(压痕尖端)的再结晶形核行为。先通过测量一个选择区域的变形组织,然后退火并测量上述区域的微观组织结构,以研究样品内部的微观组织结构对形核的影响。研究结果表明:晶核由变形组织内高储存能处的孕育区发展演变而来,通过孕育区大角晶界快速迁移而进一步长大;所有晶核与变形态内孕育区的取向相同;晶核与变形基体间小于5°的晶界阻碍晶界的进一步长大。
[Abstract]:During annealing of deformed metal, a new distortionless small grain is formed in the deformed matrix, which is called recrystallization nucleation. Industrial practice shows that recrystallization determines the fine process and final properties of thermal machining of metal products. The theory of metal recrystallization is also one of the most basic scientific problems in material science. Due to the complexity of the deformed structure of metal and the loss of evidence of recrystallization due to the disappearance of deformed microstructure, the deformed microstructure is transformed into recrystallized crystal nucleus. It is very difficult to study the mechanism of recrystallization nucleation. In this paper, the recrystallization nucleation problem in deformed face-centered cubic metals is studied by using cold rolled columnar nickel and high-purity aluminum samples with cold rolling and then microhardness indentation. Light microscopy, backscattered electron diffraction (EBSD), electron channel contrast (Ecc) and synchrotron radiation differential X-ray technique (DAXM) indicate the change of microstructure in different dimensions. The mechanism of recrystallization nucleation and the effect of local microstructure on nucleation were studied. The nuclei are mainly formed at the tri-grain boundaries and grain boundaries. Most of the nuclei are similar to the surrounding deformed matrix or twinned with one of the surrounding deformed substrates. Only a few nuclei have new orientations different from the deformed matrix. Hardness tests near the tri-grain boundary show that the greater the difference between the hardness of the three grains at the tri-grain boundary, The easier it is to nucleate at this tri-boundary, the more complex crystal orientation rotation patterns appear near the indentation tip in high-purity aluminum samples that are cold-rolled and indented with microhardness. In a series of grains with no original orientation, After cold rolling, the average hardness and nucleation rate of high energy grains in the reservoir are higher. In general, the higher the hardness, the more likely the indentation nucleation is. In addition, the orientation of the nucleation formed at different indentation points of the same grain is not disordered. Instead, they gather in a certain orientation space. The orientation distribution range near the tip of the deformed indentation, It contains the orientation of nucleation formed in annealing. Using advanced synchrotron radiation-based DAXMfor the first time, the recrystallization nucleation behavior inside the sample (high purity aluminum) (indentation tip) has been characterized in situ for the first time. Measuring the deformed structure of a selected area, The microstructure of the above region was then annealed and measured in order to study the effect of the microstructure on nucleation. The results showed that the nucleation evolved from the inoculation region with high storage energy in the deformed microstructure. Through the rapid migration of the large angle grain boundaries in the inoculation region, the grain boundaries are further grown; the orientation of all the nuclei is the same as that of the inoculation regions in the variable morphology; the grain boundary less than 5 掳between the nuclei and the deformed matrix hinders the further growth of the grain boundaries.
【学位授予单位】：重庆大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG111

【相似文献】