采用表面机械研磨处理(SMAT)在AISI 304不锈钢上制备出纳米结构表层,用透射电镜(TEM)研究组织演变过程,晶粒细化机理可归纳如下:位错在{111}面上滑移并相互交割形成网格结构;单系孪晶形成并逐渐过渡到多系孪晶;多系孪晶相互交割使晶粒尺寸不断减小,并在孪晶交叉处形成了马氏体相;孪晶系增多与孪晶重复交割强度加大使得细化晶粒的尺寸进一步减小;最终在大应变量、高应变速率和多方向重复载荷的作用下,形成等轴状、取向呈随机分布的马氏体相纳米晶组织。

Nanostructured surface layer was synthesized on an AISI 304 stainless steel by using surface mechanical attrition treatment (SMAT), the microstructural evolution was examined by using the transmission electron microscope (TEM). A grain refinement mechanism was proposed as follows: dislocations slip in the {111} plane and intersect to form dislocation grids. One-system twins form and develop gradually to multi-system ones. Twin-twin intersections reduce the grain size and induce martensite transformation. With the increment of the twin systems and the enhancement of the twin intersection activities, grains are further refined. Finally, nano-scale martensite phase with equaixed shape and random crystallographic orientations forms upon the much larger strain, high strain rate and multidirectional repeated loads.