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Mechanical behaviour of zirconia–mullite directionally solidified eutectics
Highlights Directionally solidified ZrO2-mullite eutectic grown by laser floating zone. Ultra-fine eutectic morphology. A remarkable hardness value of 21.2GPa for the fastest as-grown fibres.
Abstract Laser floating zone technique (LFZ) is used to grow directionally solidified eutectic (DSE) zirconia–mullite composite fibres (30:70 in wt.%). A notable increase in hardness is observed from 11.3 to 21.2GPa as the pulling rate increases from 10 to 500mm/h, due to the ultra-fine eutectics developed at very high growth rates. The indentation fracture toughness reaches a maximum value of 3.5MPam1/2 for the fibre pulled at 100mm/h, almost three times the value of 1.2MPam1/2 determined for LFZ single-crystal mullite. The eutectic dendrites that develop along the growth direction are immersed in a glassy phase whose brittleness is counteracted by the beneficial ultra-fine morphology, giving a bending strength maximum of 534MPa. Yet, the soft nature of the glassy matrix prevails at the high temperature testing (1400°C), causing a decrease to about one-half of the RT value in the fibres with less glassy phase content.
Mechanical behaviour of zirconia–mullite directionally solidified eutectics
Highlights Directionally solidified ZrO2-mullite eutectic grown by laser floating zone. Ultra-fine eutectic morphology. A remarkable hardness value of 21.2GPa for the fastest as-grown fibres.
Abstract Laser floating zone technique (LFZ) is used to grow directionally solidified eutectic (DSE) zirconia–mullite composite fibres (30:70 in wt.%). A notable increase in hardness is observed from 11.3 to 21.2GPa as the pulling rate increases from 10 to 500mm/h, due to the ultra-fine eutectics developed at very high growth rates. The indentation fracture toughness reaches a maximum value of 3.5MPam1/2 for the fibre pulled at 100mm/h, almost three times the value of 1.2MPam1/2 determined for LFZ single-crystal mullite. The eutectic dendrites that develop along the growth direction are immersed in a glassy phase whose brittleness is counteracted by the beneficial ultra-fine morphology, giving a bending strength maximum of 534MPa. Yet, the soft nature of the glassy matrix prevails at the high temperature testing (1400°C), causing a decrease to about one-half of the RT value in the fibres with less glassy phase content.
Mechanical behaviour of zirconia–mullite directionally solidified eutectics
Carvalho, R.G. (Autor:in) / Oliveira, F.J. (Autor:in) / Silva, R.F. (Autor:in) / Costa, F.M. (Autor:in)
16.04.2014
6 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
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