| The nanocrystalline nickel coating with a relatively narrow size distribution ranging from 20 nm to 60 nm was produced by electrodeposition on the mild steel substrate. Effects of annealing time on microstructure and microhardness evolution of the as-deposited nanocrystalline nickel coating at 150 œC were investigated. The results showed that a four-hour low temperature annealing has no obvious effect on the (200) preferred orientation of the as deposited coating. Further quantitative X-ray analysis based on line broadening revealed grain growth occurs in spite of annealing the sample at a relative low temperature. The Vickers microhardness indicated that the as-deposited nanocrystalline nickel coating exhibits a combination of annealing hardening followed by annealing softening with increasing annealing time. It was suggested the annealing hardening was mainly due to grain boundary relaxation for the sample annealed within 60 min, while the annealing softening was mainly due to grain coarsening for the sample annealed beyond 60 min. |
full paper (pdf, 448 Kb)