Role of wollastonite additive on density, microstructure and mechanical properties of alumina

Wollastonite is a low fusing material and has a considerable effect on the densification of alumina bodies at sintering temperatures ranging from 1300 to 1450 °C. The wollastonite acts as a flux and accelerates the liquid forming process leading to lower temperature densification. The addition of 1.0 wt.% wollastonite alters the microstructure to form well-defined grains with an average grain size in the range of 3.0–5.0 μm. The grains are distributed uniformly and the fracture occurs along the grain boundaries and the microstructure reveals the presence of highly dense and sintered grains. The hardness and bend strength for 0–5.0 wt.% wollastonite increases from 8.5 to 14 GPa and from 119 to 249 MPa respectively at a sintering temperature of 1400 °C.