On the strength and ductility of nanocrystalline materials

In the early 1990s, there was a widespread belief that metals, ceramics and intermetallics with the grain size in the nanometer range would exhibit the unique combination of ultra-high strength and high ductility at ambient temperatures. However, the hopes for ultra-strong and ductile nanocrystalline materials have not materialized. Experimental and theoretical studies point to inherent limitations of the strength and ductility of nanocrystaline materials.