Tarrant, Luke (2012)
Eng.D. thesis, University of Birmingham.
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The relationship between the formulation of ceramic mould materials for investment casting and their mechanical properties was investigated. A number of different ceramic materials were employed throughout the investigation including alumina, zirconia, mullite and colloidal silica. Ceramic shell specimens were investigated by measuring mechanical strength using flexural and compressive testing with the former being conducted at both room and elevated temperatures. Samples were further investigated by thermal expansion measurement and Archimedes porosity measurement.
It was determined that the incorporation of unstabilised zirconia as both a stucco and filler material was effective in terms of reducing the fired strength of investment casting ceramics. Structural observations of samples under SEM revealed that the weakened samples featured significant cracking in the fired condition due to the occurrence of the zirconia phase transition. Thermal expansion measurements confirmed both the presence of the phase transition and the extent of the disruption caused.
It was observed for slurries containing silica and alumina, that variation of the proportions of either had a significant effect on the properties of the final shell material. It was also shown that the size of the ceramic particles within the slurry had a significant effect on the final properties of the ceramic body.
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