Alumina (Al2O3) has excellent heat resistance and corrosion resistance compared to other ceramic materials and the highest strength among the oxides because of its strong ionic bonds. However, despite those excellent characteristics, its application as a structural material is difficult owing to the...
Alumina (Al2O3) has excellent heat resistance and corrosion resistance compared to other ceramic materials and the highest strength among the oxides because of its strong ionic bonds. However, despite those excellent characteristics, its application as a structural material is difficult owing to the high sintering temperature during the manufacturing process and intrinsic high brittleness of alumina. Yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP), which contains only the 100% tetragonal crystal phase because it is formed from a 2–3 mol% solid solution of Y2O3, has a relatively low sintering temperature. Because sintering is easy and the tetragonal crystal phase can be entirely transformed to the monoclinic crystal phase, the strength and toughness increase dramatically. Furthermore, because the manufacturing process is relatively simple, 3Y-TZP is widely used as a structural material. Therefore, in this study, zirconia-toughened alumina (ZTA) specimens that show good mechanical properties even at low temperatures were fabricated by adding different 3Y-TZP contents, and the microstructure and mechanical properties of specimens sintered at 1400, 1500, and 1600C were observed. As the 3Y-TZP content increased, the bulk density increased; accordingly, the fracture toughness also increased gradually. However, as the 3Y-TZP content became higher than the alumina content, the Vickers hardness value decreased, and when the 3Y-TZP content was 40 wt%, a high hardness value of 1,946 Hv was observed. The corresponding flexural strength was 342 MPa, which was the highest value obtained. When 3Y-TZP was added, the ZrO2 particles were located between Al2O3 grains, and when sintered, alumina and zirconia each suppressed particle growth of the other. The uniform dispersion of zirconia is determined to cause fracture toughness through crack deflection.
Alumina (Al2O3) has excellent heat resistance and corrosion resistance compared to other ceramic materials and the highest strength among the oxides because of its strong ionic bonds. However, despite those excellent characteristics, its application as a structural material is difficult owing to the high sintering temperature during the manufacturing process and intrinsic high brittleness of alumina. Yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP), which contains only the 100% tetragonal crystal phase because it is formed from a 2–3 mol% solid solution of Y2O3, has a relatively low sintering temperature. Because sintering is easy and the tetragonal crystal phase can be entirely transformed to the monoclinic crystal phase, the strength and toughness increase dramatically. Furthermore, because the manufacturing process is relatively simple, 3Y-TZP is widely used as a structural material. Therefore, in this study, zirconia-toughened alumina (ZTA) specimens that show good mechanical properties even at low temperatures were fabricated by adding different 3Y-TZP contents, and the microstructure and mechanical properties of specimens sintered at 1400, 1500, and 1600C were observed. As the 3Y-TZP content increased, the bulk density increased; accordingly, the fracture toughness also increased gradually. However, as the 3Y-TZP content became higher than the alumina content, the Vickers hardness value decreased, and when the 3Y-TZP content was 40 wt%, a high hardness value of 1,946 Hv was observed. The corresponding flexural strength was 342 MPa, which was the highest value obtained. When 3Y-TZP was added, the ZrO2 particles were located between Al2O3 grains, and when sintered, alumina and zirconia each suppressed particle growth of the other. The uniform dispersion of zirconia is determined to cause fracture toughness through crack deflection.
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#ZTA substrate
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