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(duì)純鋁進(jìn)行表面機(jī)械研磨處理形成納米層,用XRD、TEM對(duì)表面納米層進(jìn)行了表征,并對(duì)沿深度方向的硬度變化進(jìn)行分析.結(jié)果表明:晶粒細(xì)化后的主要微觀特征是在原始晶粒內(nèi)形成位錯(cuò)纏結(jié)、位錯(cuò)胞和高密度位錯(cuò)墻;隨著應(yīng)變的增加,這些位錯(cuò)組態(tài)逐漸演變成位錯(cuò)胞、亞晶、位錯(cuò)墻-顯微帶結(jié)構(gòu)和層狀胞塊結(jié)構(gòu);隨著應(yīng)變和應(yīng)變速率的進(jìn)一步增加,晶粒細(xì)化遵循逐漸細(xì)分原則,逐漸在表面形成隨機(jī)取向的納米晶;與試樣心部硬度相比,其表面硬度明顯提高.