Hardness and fracture toughness of alumina-based particulate composites with zirconia and strontia additives
AbstractThis project aims to study characteristics and mechanical properties i.e. hardness and fracture toughness of alumina matrix composite materials containing zirconia and strontium oxide. Two groups of composite specimen were fabricated: (i) Al2O3 matrix with 3 mol% Y2O3- ZrO2, varied from 10, 20, 30 and 40 vol%, and (ii) Al2O3 matrix with 2, 5, 10 and 15 vol% SrO added in the form of SrCO3. The powders were blended and then pressed into pellets. The compacts were pressureless sintered at 1600 ÂºC for 2 hours in air. Density measurement of the sintered composites was carried out using liquid immersion. Hardness and fracture toughness were carried out using the Vickers indentation. Microstructure was observed using scanning electron microscopy and phase content was detected by mean of X- ray diffraction. The Al2O3 containing ZrO2 forms finer alumina grains along with phase transformation, leading to higher toughness. Meanwhile, the Al2O3 containing SrO forms elongated grains, enhancing toughness due to crack deflection. Then, the blend between Al2O3-ZrO2-SrO composites was assumed whether a combination of them both may improve the mechanical properties. It was found that an addition of SrO and ZrO2 in the same Al2O3 matrix could not provide better hardness, but could improve fracture toughness compared to the two component composites.
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