Analysis of effects of fine nanoparticles and grain boundary character distribution on abnormal grain growth in friction stir welded material

搅拌摩擦焊材料在搅拌摩擦焊后热处理过程中，焊缝区组织中经常出现异常晶粒生长（AGG）现象。在本研究中，研究了微观结构特征对GG的影响，以防止AGG。纳米颗粒的加入对AGG的抑制效果较好。并考虑通过优化焊接条件，控制晶界特征的分布，防止焊渣的产生。通过调整合金元素和纯度，可以控制晶粒尺寸。研究结果对提高fswwe材料的可靠性具有重要意义。

In the friction stir welded (FSW) material, the abnormal grain growth (AGG) often occurs in the microstructure of the weld zone during the post-FSW heat treatment. In this study, the influence of microstructural features on GG was investigated to prevent the AGG. The addition of fine nanoparticles was effective for preventing the AGG. And also it was considered to prevent GG by controlling the grain boundary character distribution by the optimization of welding condition. In addition, it was confirmed that the grain size can be controlled by adjusting the alloying element and the purity level. It is concluded that these results are very important to improve a reliability of FSWed material.