Influences of metallic Co and mechanical alloying on the microstructural and mechanical properties of TiB ₂ ceramics prepared via pressureless sintering

This study reports the influences of metallic cobalt (Co) and mechanical alloying (MA) on the microstructural and mechanical properties of TiB ₂ ceramics prepared by using a combined method of cold pressing and sintering. The effects of Co addition (0, 5, 10 and 20wt.%) and mechanical alloying duration (0, 3, 6 and 9h) on the properties of TiB ₂ ceramics were investigated. MA experiments were carried out in a Spex™ 8000D Mixer/Mill and milled powders were subsequently compacted to cylindrical preforms by uniaxial pressing at 400MPa. The green compacts were sintered in a controlled atmosphere at 1550°C for 1h. Phase and microstructural characterizations of the mechanically alloyed (MA'd) and sintered samples were performed by X-ray diffractometer (XRD), optical microscope (OM) and scanning electron microscope (SEM). Density measurements were conducted using Archimedes method. Vickers hardness, elastic modulus and fracture toughness of the sintered samples were measured using Indentation technique.