Relation between Surface Appearance and Coefficient of Friction in Compressive Deformation of Metals

The compression test was performed on aluminium, copper, mild steel, stainless steel and aluminium single crystal by using various lubricants. The following results were obtained from the relationship between the microscope pattern of the compressed surface and the frictional coefficient : (1) The surface pattern of the plate after rolling is similar to that of the specimen after compression. (2) In the case of a large frictional coefficient, a glossy surface appears in the specimen in which a greater part of the surface is in contact with tools. In the case of a small frictional coefficient, a dull face having a rugged surface of a few microns in depth appears. It seems likely that there is a fluid film in the sinks. (3) In the 60% deformation of the various materials by using palm oil as a lubricant, the ratio of the surface covered by the fluid film to the total friction surface is 75～85% for aluminium or copper and about 10% for stainless steel. (4) From the compression test it is conceivable that there are deformation bands in the rugged surface of the dull face, which the lubricants fill. This phenomenon may be one of the great differences between the sliding friction and the compression deformation