Micrometer size grains of hot isostatically pressed alumina and its characterization

Alumina samples were prepared from two different particle size powders. Finer particle compacts when heated along with coarser particle compacts at same processing temperatures produce bigger grain microstructures due to higher grain growth. An unconventional method of etching by molten V₂O₅ was adopted to look at the microstructure for accuracy in reported data. On an average starting with finer particles give microstructure with a grain size of 5.5 μm and starting with coarser particles, give microstructure with 2.2 μm average grain size. The flexural strength is around 400 MPa for alumina samples prepared from finer powder in comparison with about 550 MPa for alumina samples prepared from coarser powder. The Vickers hardness in 5.5 μm grain microstructure is around 20 GPa in comparison to about 18 GPa in microstructure with smaller grains of 2.2 μm size.