Effect of Z Values on the Microstructure and Mechanical Properties of Post-sintered Reaction Bonded β-SiAlON

beta-SiAlON materials with different Z values (Z = 0.5-3) were fabricated by a reaction bonding combining post-sintering route using raw materials of Si, Al2O3, AlN, etc. The reaction bonded beta-SiAlON (RB-beta-SiAlON) were post-sintered at 1,750 C-circle for 6 h. Apparent porosity, bulk density, bending strength and Vicker's hardness of the samples before and after post-sintering were tested. XRD results showed that the phase composition of both RB-beta-SiAlON and post-sintered RB-beta-SiAlON (PSRB-beta-SiAlON) were beta-SiAlON. For RB-beta-SiAlON, the apparent porosity was decreased with the increase of Z values, while the strength and hardness was increased accordingly. After the post-sintering procedure, nearly full densified PSRB-beta-SiAlON was obtained and the mechanical properties were significantly improved. The bending strength and Vicker's hardness of the PSRB-beta-SiAlON (Z = 0.5) achieved 510 MPa and 16.5 GPa, respectively, which were as 2.7 and 6.7 times high as those of the corresponding RB-beta-SiAlON. However, the strength and hardness of PSRB-beta-SiAlON decreased with the increase of Z value due to the grain growth.