The Nature of Mechanically Polished Surfaces of Copper

Surfaces of copper polished with diamond abrasives were examined by transmission electron microscopy; surfaces abraded on silicon carbide papes were also studied for comparison. There was no evidence of an amorphous layer, known as the Beilby layer, on any of the polished surfaces; the surface layers were crystalline and all showed evidence of plastic deformation. Slab-shaped cells were present at the surfaces that appear to correspond to the microbands or shear bands that have been observed in heavily cold-rolled copper. Some recrystallization occurred in the surfaces polished with 6-μm diamond abrasive, indicating some relaxation and modification of the microband-shear band structure; small subgrains were also observed, and it is concluded that they were also recrystallized grains. The degree of deformation at the surface decreased with increasing fineness of polish (i.e., from 6-μm diamond abrasive to 1 μm). The abraded surfaces consisted almost entirely of small subgrains, indicating that the shear band structure at these surfaces had nearly all recrystallized. It was concluded, however, that the highest surface temperature was attained when polishing with 6-μm diamond abrasive and then was only 100-150°C.