The influence of grain size and texture on the Young's modulus of nanocrystalline nickel and nickel–iron alloys

Abstract

Hardness and Young's modulus were measured by nanoindentation on a series of electrodeposited nanocrystalline nickel and nickel–iron alloys. Hardness values showed a transition from regular to inverse Hall–Petch behaviour, consistent with previous studies. There was no significant influence of grain size on the Young's modulus of nanocrystalline nickel and nickel–iron alloys with grain sizes greater than 20 nm. The Young's modulus values for nanocrystalline nickel and nickel–iron alloys for grain sizes less than 20 nm were slightly reduced when compared to their conventional (randomly oriented) polycrystalline counterparts. The observed trend with decreasing grain size was found to be consistent with composite model predictions that consider the influence of intercrystalline defects. However, there was some notable variability of the measured values when compared to the model predictions. Three theoretical relationships were used to characterise the anisotropic elastic behaviour of these materials. As a result, texture was also considered to have an influence on the measured Young's modulus and used to explain some of the observed variability for the entire grain size range (9.8–81 nm).

Keywords:

• nanocrystalline
• nanoindentation
• nickel
• nickel–iron alloy
• hardness
• Young's modulus
• grain size
• texture

Acknowledgements

The authors would like to thank Shimadzu for the generous donation of the nanoindenter and Dr. Y. Zhou for his contributions. Financial support from the Natural Sciences and Engineering Research Council of Canada, the Ontario Graduate Scholarship, and the Ontario Research Fund (ORF-RE) is gratefully acknowledged.