Characterization of AI_2O_3-AI_2TiO_2 Ceramic Composites: Effects of Sintering Parameters on the Properties

摘要

This study aims to evaluate the effects of sintering parameters in crystalline phases, microstructure and mechanical properties of composites obtained through the Alsub2/subOsub3/sub-TiOsub2 /subceramic system. Cylindrical specimens, containing molar ratio of 3 Alsub2/subOsub3/sub: 1 TiOsub2/sub, were uniaxially pressed at 100 MPa. The applied sintering parameters were varied in five distinct temperature ranges (1300°C, 1400°C, 1500°C, 1575°C or 1600°C) for 2h and 1600°C for 10h. After sintering, samples were characterized by relative density, X-ray diffraction, scanning electron microscopy and mechanical properties (hardness and fracture toughness). After sintering the results point to a microstructure with grains near to 2.5mm, independent of the present phases and crystalline phases composed of: Alsub2/subOsub3/sub rhombohedral, TiOsub2/sub tetragonal e Alsub2/subTiOsub5/sub orthorhombic. The specimens sintered at 1600°C-10h feature densification 30% higher them the ones sintered at 1300°C-2h, reaching a density higher than 85% of theoretical density. The composite presents hardness higher than 1000HV and fracture toughness upper than 2.2MPamsup1/2/sup. The better results for the mechanical properties were found in the composites sintered at 1600°C-10h, that showed a bigger relative density than all analyzed specimens, and only phases of Alsub2/subOsub3/sub and Alsub2/subTiOsub5/sub could be found, what means that all TiOsub2/sub was consumed in the sintering of the new composite.