A nanostructured surface layer was formed on pure Al 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 walls (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.

對純鋁進行表面機械研磨處理形成納米層,用XRD、TEM對表面納米層進行了表征,并對沿深度方向的硬度變化進行分析.結果表明:晶粒細化后的主要微觀特征是在原始晶粒內形成位錯纏結、位錯胞和高密度位錯墻;隨著應變的增加,這些位錯組態逐漸演變成位錯胞、亞晶、位錯墻-顯微帶結構和層狀胞塊結構;隨著應變和應變速率的進一步增加,晶粒細化遵循逐漸細分原則,逐漸在表面形成隨機取向的納米晶;與試樣心部硬度相比,其表面硬度明顯提高.