It is well known that formation of nanocrystalline (NC) structure in different materials leads to remarkable properties. Many investigations of NC materials show that they have substantially different physical and mechanical properties not only because of the grain size but also because of the structure of grain boundaries as well /1-4/.
One of the methods of severe plastic deformation for producing ultra-fine-grained (UFG) material is Equal-Channel Angular Pressing (ECAP). A commercial Al-Mg-Si alloy (6082) is deformed by equal-channel angular pressing (ECAP) to produce a bulk ultra-fine-grained structure using route C technique up to eight passes with a high length to diameter ratio of 15-16. The products were investigated after one, four and eight passes. The upsetting test is used to determine the true stress-true strain curves in all of the three conditions.
The results show that the number of ECAP passes have significant effect on the behaviour of the stress strain curve of the ECAP material. During upsetting, the anisotropy induced by the ECAP technology has led to asymmetrical bulging/buckling
This phenomenon is reduced by controlling the height/ diameter ratio of the upsetting specimens.
Keywords: nanostructure materials, true stress strain curves, equal-channel angular pressing (ECAP)