Densification behaviour and microstructural evolution of TiO2/CAS-incorporated alumina

Densification behaviour and microstructural evolution of TiO2/CAS (CaO-Al2O3-SiO2)-incorporated alumina has been investigated systematically. The experimental results show that TiO2 can greatly enhance the densification rates of alumina but trigger severely abnormal grain growth (AGG) at 0.60 wt%. On the other hand, small amounts of CAS can effectively inhibit abnormal grain growth, but provoke an abnormal densification owing to the formations of in situ pores left by liquid phase. With additional 0.50 wt% of CAS incorporated into 0.60 wt% TiO2-doped sample, the aspect-ratios of anisotropic growth grains increase by reduced growth rates of flat boundaries, accomplished by basal planes much smoother and straighter. This microstructure subsequently disappears when CAS incorporation is up to 4.0 wt%, substituted by that with low aspect-ratio and fine-equiaxed grains. Such occurrences are discussed in term of levels of liquid phase and 2-dimension (2-D) nucleation processes.