【作者】 李茂林；

【导师】 胡兰青；

【作者基本信息】 太原理工大学 ， 材料学， 2006， 硕士

【摘要】 纳米晶材料由于结构独特，性能优异而倍受关注。但是由于制备技术和团聚问题等未能解决，目前难以获得高纯，致密，界面清洁的理想三维块体纳米晶材料。随着对纳米材料研究的不断深入与纳米技术的不断发展，将表面改性与纳米技术相结合来制备纳米晶块体材料得到了人们的广泛重视。这样可以通过提高材料表面性能来提高材料的整体性能。目前通过表面高能喷丸技术，在金属材料表面已经成功制备出一定厚度的纳米结构表层，即实现了表面纳米化。然而对于金属材料表层纳米结构的微观组织演变，性能与结构的关系尚缺乏系统的认识和深入的理解。因此，深入系统的研究强烈塑性变形导致的纳米晶粒形成机制和技术对纳米材料合成与应用具有十分重要的意义。 本论文研究了表面高能喷丸方法制备纳米晶块体材料的工艺技术和纳米化机理。采用金相显微镜，X-射线衍射仪(XRD)，透射电子显微镜(TEM)和高分辨电子显微镜(HRTEM)等测试设备系统的研究了表面高能喷丸处理后Al-Zn-Mg合金表面层不同深度的微观结构特征，测试了表面层不同深度的硬度分布。根据表面层应变引入的微观结构特征，提出了Al-Zn-Mg合金表面高能喷丸导致晶粒细化的机制。 主要研究结果如下： 1．Al-Zn-Mg合金经过表面高能喷丸处理后，表层形成了等轴、随机取向的纳米晶粒，最小晶粒平均尺寸约为20nm。表面层微观结构随更多还原

【Abstract】 Increasing interests have been focused on nanocrystalline (nc) materials during the past decade with the anticipation that their properties will be different from,and often superior to those of conventional coarse-grained materials. However,difficulties exist in obtaining "ideal" (i.e.,flaw-free,contamination-free,residual stress-free and with a sufficiently large sample size) nc samples by using the present preparation techniques. With increasing evidences of novel properties in nc materials,it is reasonable to propose to achieve surface modification by the generation of a nanostructured surface layer so that the overall properties and behavior of the material are significantly improved.A nanostructured surface layer has been successfully obtained in many material systems.Nevertheless,up to now,a clear scenery of microstructures and properties of the nanostructured surface layers,especially formation of nano sized crystallites from coarse polycrystals during plastic deformation,is still lacking. Therefore,understanding of the underlying mechanism for grain refinement by severe plastic straining is becoming more and more crucial.In this work,microstructural characteristic at different depths of the nanostructured surface layer in Al-Zn-Mg alloy sample induced by surface high energy shot peening(HESP) treatment was investigated by means of更多还原