Progress in mechanical properties of gradient structured metallic materials induced by surface mechanical attrition treatment

Abstract

It is well known that the bulk nanostructured metallic materials generally exhibit high strength but poor ductility, which greatly hinders their applications. In most cases, material failures usually start from the surface. Therefore, the surface modification is crucial to improving the mechanical properties of metallic materials. The surface mechanical attrition treatment (SMAT) is one of the most effective surface modification methods. It can be used to manufacture gradient nanostructured materials that there is no interfaces between the surface and the coarse-grained matrix. Additionally, the gradient nanostructured metallic materials fabricated by SMAT exhibit a preferable combination of strength and ductility compared with conventional homogeneous materials. It is generally believed that the high strength of the SMAT-ed metallic materials is owing to the surface fine-grain strengthening. Whereas the improved ductility can be attributed to the coarse-grained matrix and the superior work hardening ability of the gradient structured (GS) materials. In this overview, the research progress of the GS metallic materials fabricated by SMAT is summarized. It mainly introduces the microstructure characteristics of the GS layer and the mechanical properties of GS metallic materials. Finally, in order to find the optimal match between the strength and ductility in the GS materials, the several factors affecting the mechanical properties of GS materials are summarized.