Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《材料研究学报》
Abstract: A gradient and nanostructured (GNS) surface layer was formed on a 316L stainless steel sample by using surface mechanical rolling treatment (SMRT). The effect of SMRT on the evolution of phase composition and microstructure was studied of the GNS surface layer. The results show that deformation- induced martensite transformation occurs in the surface layer after SMRT, and the martensite amount increases with the increasing penetration depth of SMRT. The microstructural refinement mechanism includes subsequently the formation and interaction of various dislocations, deformation twinning, deformation- induced martensite transformation, and martensite refinement. Finally, nanostructure with mostly martensite and a mean grain size of ca. 55 nm was achieved in the topmost surface layer of the 316L sample.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract: A gradient nanostructured (GNS) surface layer was fabricated on a Z5CND16-4 martensitic stainless steel by means of surface mechanical rolling treatment (SMRT). The microstructure in the GNS surface layer was characterized by using SEM and TEM. The results showed that the mean grain size increases with depth, from about 25 nm at the topmost surface layer to the initial value in the matrix. The total thickness of the grain-refined layer is about 150 mm. The electrochemical corrosion property of the SMRT sample was compared with that of the as-received sample in a 3.5%NaCl aqueous solution. It is shown that the pitting corrosion potential increases from about 0.179 V in the as-received sample to about 0.313 V in the SMRT sample, and the self-corrosion potential also increases evidently. The formation of nanostructures, the increased structural homogeneity, and the introduction of compressive residual stresses in the GNS surface layer, as well as the decreased surface roughness, were discussed to promote the pitting corrosion resistance of the SMRT sample.