超音速微粒轰击45钢表面纳米化的研究

Surface nanocrystallization of 45 steel induced by supersonic fine particles bombarding

采用超音速微粒轰击技术（SFPB）对由铁素体和珠光体组成的45钢进行表面纳米化处理,在材料表面制备了纳米结构表层,利用X射线衍射、扫描电镜、透射电镜等分析技术研究了表面纳米结构层不同深度的微观组织结构特征.研究表明：经SFPB处理后,材料表层发生了严重的塑性变形,形成了由铁素体和渗碳体组成的纳米结构层;随着处理时间的增加纳米结构层的厚度由几微米增加到15μm（晶粒尺寸〈100 nm）;在材料的最表层形成了晶粒尺寸约15 nm的具有随机取向的等轴晶,纳米晶粒尺寸随着距表面距离的增加增大;在距表面约为15μm处,存在平均晶粒尺寸约100 nm的等轴晶和具有相近尺寸的胞状结构;在约30μm处,大量的高密度位错墙分别将铁素体相和珠光体相分割成尺寸在200~500 nm的胞状结构.分析表明45钢表面纳米化主要是位错运动的结果.

By means of Supersonic Fine Particles Bombarding（ SFPB）, a nanostructured surface layer was fabricated on a 45 Steel plate composed of pearlite and ferrite phases. The microstructure features of various sections in the surface layer were characterized by using XRD, SEM, TEM observations. After SFPB treatment, severe plastic deformation was observed and a nanostructured surface layer composed of ferrite and cementite phases was found; The thickness of nanostructured surface layer varied from a few to about 15μm（ grain size 〈 100 nm） depending upon the treatment duration; At the top surface layer, the mean size of equiaxed nano- crystallites was approximately 15 nm. The grains size increased depending upon distance from the treated surface. The equiaxed grains and cells with size of 100 nm were formed at the depth of about 15 μm; In the region from about 30 μm depth, large numbers of cell structures with size of about 200 -500 nm separated by dense dislocation walls were observed. Experimental evidence and analysis indicated grain refinement could be mainly attributed to the movement of dislocation.