The microstructure and fracture properties of MgO crystals containing a dispersed phase |
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Authors: | P Hing G W Groves |
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Affiliation: | (1) Department of Metallurgy, Oxford University, Oxford, UK;(2) Present address: School of Physics, University of Warwick, Coventry, UK |
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Abstract: | MgO crystals containing up to 40% by volume of magnesioferrite and up to 2% by volume of iron and nickel were produced by
a diffusion technique followed by appropriate heat treatments. Magnesioferrite precipitate did not significantly change the
effective surface energy of a crack as measured by the double cantilever beam technique. Iron and nickel precipitate was produced
in the form of platelets lying on {100}MgO planes whose orientation relationships were 001]MgO ∥001]Fe, 110]MgO ∥100]Fe with a spread of +10°, approximately, and 001]MgO ∥001]Ni, 010]MgO ∥010]Ni with negligible spread. Despite the crystallographic orientation relationships, the metal-MgO interface appeared to be very
weak; the reasons for this are discussed. The effect of the metal precipitate on crack propagation was to markedly increase
the density of cleavage steps. For a volume fraction of precipitate of 0.02, this led to a small increase in the effective
surface energy, on the order of 1 Jm−2. |
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Keywords: | |
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