SUPPRESSION OF FREE-SURFACE ROUGHENING OF METAL WITH PLASTIC-DEFORMATION

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 mate rial is produced with a smaller surface grain size. In the present inv estigation, a thin layer with small crystal grain size is coated On th e surface of an aluminum specimen with coarse grains and the effects o f the crystal grain size, as well as the thickness of the surface laye r, on surface roughening are evaluated in an upsetting test: It is sho wn that surface roughening is dominated only by the crystal grain size at the surface layer, and thus surface roughening can be suppressed b y coating the surface of the material with a thin layer of small cryst al grain size.