Microstructural Origin of Superior Compressive Ductility of a Nanocrystalline Metal
Ultra-large compressive plasticity at room temperature has recently been observed in electrodeposited nanocrystalline nickel (nc-Ni) under micro-scale compression (Pan, Kuwano, Fujita and Chen: Nano Lett. Vol. 7 (2007), p. 2108). With aid of a TEM sample preparation technique employing focused ion beam (FIB), TEM observations on deformed nc-Ni evidenced deformation-induced microstructural evolution of nc-Ni at a variety of strain levels: Whilst the deformation increases, substantial grain growth is uncovered in the nc-Ni. No apparent ex situ evidence of intragranular dislocation activities is found in the deformed sample. As thermal diffusion plays an insignificant role in the deformation in nc-Ni at room temperature (~0.17Tm), this premium plasticity is achieved in accommodation with the grain-boundary-mediated deformation, with assistance of extensive grain growth that is mainly driven by high stresses at steady plastic flow.
Yonghao Zhao and Xiaozhou Liao
D. Pan et al., "Microstructural Origin of Superior Compressive Ductility of a Nanocrystalline Metal", Materials Science Forum, Vols. 633-634, pp. 73-84, 2010