Grain gradient refinement and corrosion mechanisms in metals through severe plastic deformation: insights from Surface Mechanical Attrition Treatment (SMAT)

Abstract

Surface Mechanical Attrition Treatment (SMAT) is an efficient surface nano-crystallization technique that significantly enhances the corrosion resistance of various metallic materials by refining grain structure and introducing residual compressive stress. This paper provides a comprehensive review of the application of SMAT on metals, including stainless steel, magnesium alloys, and titanium alloys, focusing on its mechanisms in mitigating pitting corrosion, stress corrosion cracking, and general corrosion. The review begins by examining the effects of SMAT on residual stress, grain refinement, and surface condition modifications, followed by proposing optimization strategies for the treatment process. Through a combination of electrochemical testing, microstructural characterization, and numerical simulations, the paper highlights the pivotal role of residual compressive stress and the nanocrystalline layer in the formation of passive films and the evolution of surface oxide layers, particularly under various corrosive environments. Additionally, the paper presents a comparative analysis of corrosion mechanisms in different metals post-SMAT treatment. The treatment can also induce phase transformations, such as martensitic transformation and the formation of metastable phases, which have significant implications for corrosion behavior. Finally, the synergistic effects of SMAT when combined with other surface treatment techniques, such as micro-arc oxidation and ion implantation, are discussed, along with an evaluation of its feasibility and limitations for industrial applications. By comparing the performance and cost-effectiveness of SMAT with other techniques, this paper provides valuable insights and a solid technical foundation for the optimization of metallic materials in highly corrosive environments, such as aerospace and marine engineering.