纯铝表面机械研磨纳米化后的显微组织和硬度

Microstructure and Hardness of Pure Aluminum Surface Nanocrystallization after SMAT

对纯铝进行表面机械研磨处理形成纳米层,用XRD、TEM对表面纳米层进行了表征,并对沿深度方向的硬度变化进行分析。结果表明:晶粒细化后的主要微观特征是在原始晶粒内形成位错缠结、位错胞和高密度位错墙;随着应变的增加,这些位错组态逐渐演变成位错胞、亚晶、位错墙-显微带结构和层状胞块结构;随着应变和应变速率的进一步增加,晶粒细化遵循逐渐细分原则,逐渐在表面形成随机取向的纳米晶;与试样心部硬度相比,其表面硬度明显提高。

A nanostructured surface layer was formed on pure A1 by means of surface mechanical attrition treatment （SMAT）. The microstructure of the surface layer of the sample treated by SMAT was characterized by means of X-ray diffraction（XRD） and transmission electron microscopy （TEM）. Hardness variation along the depth direction was tested. The results showed that the grain refinement process at the surface layer involves formation of dislocation tangles （DTs）, dislocation cells （DCs） and dense dislocation wails （DDWs） in original grains. With the increase of strain the dislocation walls and tangling transformed into dislocation cells, subgrains, dense dislocation walls-microbands （DDWs-MBs） and lamellar boundaries （LBs）. With the increase of strain and strain rate further, grains were subdivided on a smaller scale and finally equiaxed nanocrystallites with random crystallographic orientations were formed. The hardness of nanostructured surface layer was enhanced significantly after SMAT compared with that of the initial sample.