Nanoscale plastic deformation and residual stress in metals due to surface polishing

This project aims at studying plastic surface deformation due to mechanical polishing of metals, as well as the induced residual stress field. Mechanical polishing is commonly used for both surface finishing and metallographic sample preparation for a broad range of materials. In metals, however, polishing leads to the formation of a modified surface layer due to plastic deformation, which also induces subsurface residual stress. This has an impact on many material properties and on characterization techniques that rely on surface measurements. There has not yet been a systematic study to investigate the effect of polishing and material parameters on this surface alteration, nor the possible variations between grains or phases. We will examine these phenomena quantitatively for a strategic range of metallic specimens, using novel nanoscale surface analysis techniques. An unconventional polishing approach will be followed, starting from pristine electropolished surfaces prior to mechanical polishing, in order to determine the impact of individual polishing parameters. The influence of material properties will be clarified systematically by examining pure metals with inherently different hardness, by modifying the grain size and probing individual grains, and by examining specific alloys. This will result in fundamental insights regarding surface layer modifications in metals due to polishing, which will serve as a basis for a wide array of future research.