Grain-boundary strengthening in nanocrystalline chromium and the Hall–Petch coefficient of body-centered cubic metals

Nanocrystalline Cr (nc-Cr) was synthesized by electrodeposition. Samples with various grain sizes (19–57 nm) were prepared by annealing the as-deposited sample. Microstructures were examined using X-ray and electron microscopy, and the mechanical properties were evaluated using nanoindentation. The strength of nc-Cr samples apparently obeyed the classical Hall–Petch relationship. It was found that hardening potency caused by grain refinement was generally higher in body-centered cubic metals than that in face-centered cubic and hexagonal close-packed metals. A possible explanation was offered.