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Alumina-Zirconia (Al 2 O 3 -ZrO 2 ) composites especially Zirconia Toughened Alumina (ZTA) shows better mechanical properties over alumina. Al 2 O 3 -ZrO 2 composites were prepared by powder compaction method varying 3 mol% yttria stabilized zirconia (3Y-ZrO 2 ) content from 0 to 20 vol% using small amount of MgO as sintering aid. The composites were sintered for two hours in air at 1580˚C. At this temperature maximum density was achieved 99.31% of theoretical density for composite containing 20 vol% 3Y-ZrO 2 . Density measurement of sintered composites was carried out using Archimedes's method. Hardness and fracture toughness measurement was carried out using Vickers indentation. Phase content and t-ZrO 2 retention were detected by means of X-ray diffraction (XRD). Microstructure of the composites and grain size of alumina and zirconia was determined by Scanning Electron Microscopic (SEM) analysis. Maximum microhardness (17.46 GPa) was achieved for composite containing 5 vol% ZrO 2 and maximum flexural strength (684.32 MPa) and fracture toughness (10.33 MPam 0.5 ) was achieved for composite containing 20 vol% of 3Y-ZrO 2 . The aim of the present work is to investigate the optimum 3Y-ZrO 2 content for obtaining maximum density, microhardness, flexural strength and fracture toughness of Al 2 O 3 -ZrO 2 composites.

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