Ductility of nanocrystalline materials with a bimodal grain structure

Abstract

A simple model describing the tensile deformation behavior of a nanostructured material with a combined nano- and microcrystalline grain structure has been developed. The nanocrystalline matrix ensures a high mechanical strength, while the microcrystalline grains provide an increase in the ductility of such materials. The proposed model of tensile straining of the material with bimodal grain structure predicts that the regime of uniform straining until neck formation must depend on the dimensions and volume fractions of the nano- and microcrystalline grains. It is shown that a growth in the ultimate uniform strain is related to an increase in the ratio of the yield stress to the coefficient of strain hardening and in the parameter of plastic strain distribution between the nano- and microcrystalline components.