Rolling deformation induced reduction of rate sensitivity and enhancement of hardness in nanocrystalline NiFe alloys

Abstract

Both hardness (H) and rate sensitivity (m) of nanocrystalline NiFe alloys were studied by nanoindentation testing. It was found that H increases, and m decreases after rolling in the alloys. It is interesting that the decrease in m by rolling is totally contrary to the conventional coarse grain alloys. The dislocation density is remarkably enhanced by rolling deformation, which leads to the hardening behaviour of the samples. The dislocation absorbed at the grain boundary (GB) and/or sub-GB and grain growth by rolling are responsible for the reduced m of the rolled alloys.