ABSTRACT
Fracture, cutting, grinding, and polishing of ductile materials severely plastically deforms the surface layers, probably also producing a multitude of cracks extending into the solid. All surface making operations leave defects that are ready to fall off at start of use. The structure of polished surfaces was studied by Sir George Beilby. He found, by x-ray diffraction, that no crystalline structure appeared in the polished surface. He therefore suggested that this layer might be amorphous, and it became known as the Beilby Layer. Hot rolling of metal is done at temperatures well above the recrystallization temperature and usually results in a surface covered by oxide and pock marks where oxides had been pressed into the metal and then fallen off. Cold rolling is usually done after thick scales of oxides are pickled off in an acid. This produces a smoother surface.
