Improving Fracture Toughness of Mullite Ceramics Metal Reinforcements

Abstract

Mullite/Metal composite ceramics were fabricated by the use of mechanical milling and pressureless sintering. Al2O3 + 10 vol.% of Co, Ni, or Ti were mixed and milled during 12 h at 300 rpm in a horizontal mill, then with the powder mixture it was conformed cylindrical samples by uniaxial pressing using 300 MPa. Pressed samples were sintered during 2 h in an electrical furnace at 1500°C. During sintered it was used an argon atmosphere inside the furnace in order to inhibit metal oxidation. XRD results indicate that alumina and metals retain its crystalline structure. Measurements of densities indicate that they were achieved relative densities between 90% and 98% in the manufacture composites. Optical microscopy observations show mullite’s microstructure with very fine and homogeneous distributions of metal particles. Used metals (Co, Ni and Ti) to reinforce mullite, have yielded favorable results improving the fracture toughness of the mullite. However, it should be made more dense materials with them to better explore this potential.