Abstract
Nanohardness investigations have been carried out on the plastically deformed regions around a quadrant of a 2 N Vickers microindentations in a cleaved single crystal of MgO (100) using a Hysitron machine. In all about four hundred 1 mN nanoindents were made and for each indentation an indenter load versus indenter displacement plot was obtained. Each of such plots was automatically analysed with the Hysitron machine to yield information about the nanohardness and elastic modulus. The data obtained showed that the nanohardness and elastic modulus values varied systematically with the crystallographic direction. The maximum value of nanohardness occurred at about 29 ± 1° relative to the 〈100〉 direction although higher values of hardness could possibly occur along the 〈110〉 directions if there were no cracking. Further investigations are required for understanding the variation of Young’s modulus with crystallographic orientation. Independent atomic force microscopy studies of the nanoindents are planned.
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G.K.B. would like to thank the Association of Commonwealth Universities and Government of Ghana for a postgraduate scholarship; T.A.N. would like to thank The Royal Society for a study visit to Cambridge. Y.Y.L. would like to thank The Cambridge Newton Trust for a grant.
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