In-situ alumina-zirconia composite bodies were fabricated by heat treatment of gibbsite-zircon-kaolinite mixture at 1450℃. The current research investigated crystallization behavior and mechanical properties of the mentioned mixture in the presence of 5 wt.% MgO as an additive. X-ray diffraction (XRD) results showed that alumina, zirconia, and magnesium aluminosilicate were crystallized during the heat treatment at 1250-1550℃. It was expected that mullite and zirconia were crystallized as the final phases; however, the addition of 5 wt.% of MgO changed the behavior of the mentioned mixture during the heat treatment at 1250-1550℃. Energy diffractive X-Ray spectroscopy (EDS) reported that after heat treatment at 1450℃, an Al3+-rich aluminosilicate phase was formed as the matrix of the composite. Crystallization of alumina and zirconia and the existence of the amorphous aluminosilicate phase formed a composite with appropriate hardness and mechanical strength. The diametral tensile strength and Vickers microhardness values of the final composite were 130±7 MPa and 7.49 ± 1.2 GPa, respectively.

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