Phase transformation kinetics and grain orientation of multi-cation doped (Yb, Sm) α/β-SiAlON ceramic tool materials

Abstract

The densification behavior, phase transformation kinetics, and grain orientation of multi-cation doped (Yb, Sm) α/β-SiAlON ceramic tool materials prepared via spark plasma sintering (SPS) were studied. The results indicated that the (Yb, Sm) α/β-SiAlON ceramics were rapidly densified at 1540 °C. Various intergranular phases were formed due to the doping of rare earth oxides with different ionic radii. β-SiAlON precipitated ahead of α-SiAlON and elongated rapidly above 1600 °C. The β-SiAlON grains were preferred to orient in the direction perpendicular to the SPS pressure due to the dissolution/precipitation and grain rotation mechanism. The tendency of orientation decreased with the growth of β-SiAlON grains and the increase of liquid phase. The orientation of β-SiAlON grains resulted in anisotropic mechanical properties of (Yb, Sm) α/β-SiAlON ceramics, which fracture toughness measured in the perpendicular plane (⊥) was higher than that in the parallel plane (//).