Surface Roughening During Deformation of Polycrystalline Aluminum and Titanium Alloys

The surface topography of aluminum and titanium alloys after plastic deformation is investigated using white-light interferometry. The surface profiles of tensile samples in the longitudinal and transverse directions are analyzed. The surface develops self-affine roughness on length scales up to a correlation length that is of the same order of magnitude as the grain size in the two directions. The difference in correlation lengths between the two directions is large for aluminum alloy and small for titanium alloy. Initially, the roughness values in the two directions remain the same and then become different with strain increase. It is shown that the strains in the two directions influence the profile. The relationship between the 3D surface roughness parameter (Sq) and strain appears to be linear, and a linear relation is also observed between surface area increment and strain.