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 stress of metal surface layer without any technological treatment is lower than in the bulk material. A simple mechanical model that enables one to find a yield stress distribution in the natural surface layer is proposed. As an example the natural surface layer of aluminium specimen is examined. According to the model and experimental observations, a layer thickness is equal 2-3 grains' diameters, and the yield stress in the layer may be 30% lower than in the bulk material.