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In this paper we present some initial results on pure chromium whose grain structure was refined by severe plastic deformation processing. These results include the microstructural features and the corresponding mechanical properties as a function of severe plastic deformation processing and annealing treatment. They show that severe plastic deformation is quite effective in reducing the grain size down to nanoscale dimensions with an attendant large increase in the hardness value; the hardness data is consistent with Hall-Petch strengthening. The annealing treatment demonstrated that the nanoscale microstructure is retained up to 400 °C. Further, the decrease in the hardness value with increasing annealing temperature is quite gradual up to 900 °C, suggesting that the microstructure of pure chromium, resulting from the severe deformation is not too unstable, but, it coarsens gradually with increasing temperature. Therefore, in the chromium alloys the deformed microstructure is expected to be even more stable due to the beneficial effect of the alloying additions in pinning the grain boundaries. |
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