NATURAL SURFACE-LAYER OF METALS

A notion of natural surface layer of metals as a reference state for a mechanical description of technological surface layers is introduced. According to experimental observations it is assumed that the yield s tress of metal surface layer without any technological treatment is lo wer than in the bulk material. A simple mechanical model that enables one to find a yield stress distribution in the natural surface layer i s proposed. As an example the natural surface layer of aluminium speci men is examined. According to the model and experimental observations, a layer thickness is equal 2-3 grains' diameters, and the yield stres s in the layer may be 30% lower than in the bulk material.