Micromechanics model concerning yield behavior of nanocrystalline materials

This analysis was conducted to investigate the influence that dispersion in crystal grain sizes has upon the yield behavior of nanocrystalline materials. In the model proposed for this purpose, the distribution of crystal grains was expressed in a log-normal manner. It was assumed that the yield stress of each crystal grain was determined by the relationship between the grain size and the stress required for the generation of dislocations from a grain boundary. Furthermore, using the micromechanics of inclusions, we carefully considered the internal stresses in the crystal grains yielded at a different remote applied stress and in the matrix which is still elastic. The result of the analysis showed that the increase of compliance with the yielding of crystal grains from large to small can cause the macroscopic yielding of nanocrystalline materials. It was also inferred that the distribution of crystal grains was one of the important factors which affect the shape of the stress-strain curve and the macroscopic yield stress.