Abstract
Surface roughening of metals with plastic deformation is governed not only by the strain but also by the crystal grain size of the materials. Therefore surface roughening may be expected to decrease when a material is produced with a smaller surface grain size. In the present investigation, a thin layer with small crystal grain size is coated on the surface of an aluminum specimen with coarse grains and the effects of the crystal grain size, as well as the thickness of the surface layer, on surface roughening are evaluated in an upsetting test. It is shown that surface roughening is dominated only by the crystal grain size at the surface layer, and thus surface roughening can be suppressed by coating the surface of the material with a thin layer of small crystal grain size.
