Microhardness investigations on manganese aluminate spinels

E.H.L.J. Dekker, G.D. Rieck

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Vickers microhardness measurements were carried out on single-crystalline manganese aluminates having compositions ranging from Mn1.83Al1.17O4 to Mn0.91Al2.060.03O4. Hardness increases with increasing alumina content, but the hyperstoichiometric composition shows a decline of hardness probably due to structural vacancies. In Mn1.83Al1.17O4 the crack pattern round indentations is independent of relative indenter orientation and can be accounted for by the presence of a {110} glide system. Apparent hardness anisotropy is related to the position of these glide planes in the surface. In all other harder specimens of this series, other glide systems also become operative during indentation. The occurrence of a pre-precipitation phase after the annealing of specimens is revealed by an increase in hardness, followed by a decline which is due to over-ageing.

Original languageEnglish
Pages (from-to)1839-1846
Number of pages8
JournalJournal of Materials Science
Issue number11
Publication statusPublished - 1 Nov 1974


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