Role of Local Microstructure Parameters in the Evolution Process of Interfacial Microstructures of Joints

本项目的目的是表征接头区域的微观结构，重点是微观结构参数的作用，如物相、颗粒形状和尺寸、颗粒取向和晶界结构。利用电子背散射分析技术对搅拌摩擦焊铝合金接头的微观组织进行了表征。111取向的颗粒倾向于几乎平行于旋转刀具，这表明旋转销在搅拌摩擦过程中发生了强烈的剪切变形。这种织构成分不同于传统的轧制、挤压等工艺所形成的织构成分。搅拌摩擦焊接头的组织在高温下不稳定，表现为异常的晶粒长大。搅拌摩擦焊可以在局部区域产生特殊的微观组织，但这种组织结构具有一些重要的信息，可以作为异常晶粒长大的触发效应。基于Potts模型的蒙特卡罗模拟是PE…进一步阐明了局部组织参数在均匀和非均匀温度场下单相和双相组织的晶粒长大过程中的作用。在本研究中建立了一些新的算法。晶界迁移是晶界生长的基本过程，受第二相或温度梯度的影响较大。在第二相粒子存在的区域或温度较低的区域，观察到了晶粒生长的延缓。当局部区域施加较高的温度场时，会出现异常长大等择优晶粒长大现象。这一结果为显微组织控制提供了一种新的思路，即将显微组织信息编码到多晶材料中的点加热技术。考虑到界面反应，进行了陶瓷与金属的固态扩散连接。利用化学势图的概念来描述氮化硅与钒、铌、钛和钛铝化物等金属之间的界面相序，重点研究了界面微结构随微结构参数的空间分布而变化的规律。基于本研究的结果，应该注意的是，我们可以利用应变、温度和成分的非均匀场来控制局部微观组织。较少

This project aims to characterize microstructure of joint regions focusing on the role of microstructural parameters such as phases, shape and size of grains, grain orientations and grain boundary structures. Electron Back-Scattering Pattern analysis was utilized to characterize microstructures of Aluminum alloy joint fabricated by friction stir welding(FSW). 111 oriented grains tended to exist almost parallel to the rotating tool, indicating a heavy shear deformation is taking place around the rotating pin during FSW. This texture component is different from those appeared in Al alloys fabricated by conventional processing such as rolling, extrusion and so on. The microstructure of FSW joints is unstable at elevated temperature, showing an abnormal grain growth. FSW can produce peculiar microstructure in a localized region but the microstructure has some important information to be acting as a trigger effect of abnormal grain growth.A Monte Carlo simulation based on Potts model was pe … More rformed to elucidate the role of local microstructure parameters in grain growth process of single and dual phase structures under uniform or heterogeneous temperature fields. Some new algorithms were established in the present research. Grain boundary migration, which is an essential and fundamental process for the grain growth, was strongly affected by second phase or temperature gradient. Retardation of grain growth was observed in the region where second phase particles exist or temperature was lower than the other area. Preferential grain growth such as abnormal grain growth was taking place when a steep temperature field was applied in a localized area. This result gave us a new idea for microstructure control, that is spot heating techniques for coding microstructure information into polycrystalline materials.Solid-state diffusion bonding of ceramics to metals was performed concerning the interfacial reaction. A concept of chemical potential diagram was utilized for describing phase sequence in the interfaces between silicon nitride and metals such as vanadium, niobium, titanium and titanium aluminide, and so on.The present project focused on the interfacial microstructures that show wide variety depending on the spatial distributions of microstructure parameters. Based on the findings of the present study, it should be noted that we can control local microstructure utilizing heterogeneous field of strain, temperature and compositions. Less