| Significant differences have been observed in the deformation characteristics of nanocrystalline (nc) materials at elevated temperatures as compared to their microcrystalline (mc) counterparts. This includes significantly higher flow stresses and much enhanced strain hardening rates in nanocrystalline structure. Conventional understanding on elevated temperature crystalline plasticity cannot explain these observations. In-situ TEM experiments at elevated temperatures have demonstrated the occurrence of cooperative grain boundary sliding (CGBS) in the nanocrystalline state. The rationale behind such sliding and its role in explaining nanocrystalline plasticity, including superplasticity (using Ni3Al as a model material), will be discussed in the context of the observed results. |
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