Deformation Characteristics of Nanocrystalline Metals

This chapter deals with the deformation characteristics of nanocrystalline metals. Nanocrystalline metals are useful in structural applications in which enhanced mechanical and physical properties are needed. Nanocrystalline metals exhibit different microstructures and mechanical behaviors compared to their conventional coarse-grained polycrystalline counterparts. Nanocrystalline metals possess a relatively large number of grain boundaries and can be expected to influence the mechanical properties dramatically. Moreover, nanocrystalline metals exhibit very high yield strength and hardness but limited tensile plasticity at room temperature. Limited tensile ductility results from a low strain-hardening capacity or plastic instability of nanocrystalline metals during tension and from porosity in the specimens. The rapid development of nanocrystalline metals with grain sizes in the nanometer regime presents new challenges for understanding the fundamentals of the structure-property relationship. Finally, nanocrystalline metals generally exhibit significantly high yield strength and hardness but very limited tensile plasticity. Low-tensile ductility arises from poor strain-hardening capacity, leading to earlier plastic instabilities in the form of localized deformation, such as necking and shear banding. molecular dynamics (MD) modeling has been used to simulate the mechanical deformation mechanism of nanocrystalline materials. The chapter concludes much effort is still needed to find out the suitability of MD simulations for prediction of the tensile and creep behavior of nanocrystalline metals at room temperature. © 2006 Elsevier Ltd All rights reserved.