ZHANG Jing ¹, SUN Feng ¹, ZHANG Weiru ^{1, 2}, XU Xuemin ¹, WANG Mei ¹

(1. Sinoma Advanced Nitride Ceramics Co., Ltd., Zibo 255000, Shandong, China; 2. Shandong Industrial Ceramic Research & Design Institute Co., Ltd., Zibo 255000, Shandong, China)

Abstract: In-situ toughened α-SiAlON ceramics were successfully prepared by using two-step gas pressure sintering at relatively low temperature with α-Si₃N₄ powder as raw material. The effects of La₂O₃ and Al₂O₃ on the densification, microstructure and mechanical properties of α-SiAlON ceramics were studied. With increasing proportion of La₂O₃, relative density, flexural strength and Vickers hardness of the samples decreased, while fracture toughness increased firstly and then decreased. When nY:nLa was equal to 9:1, with increasing content of Al₂O₃, relative density, flexural strength and fracture toughness of the samples increased, while the Vickers hardness decreased gradually. The above properties of the samples with 3 wt.% Al₂O₃ were 99.7%, (1202 ± 43) MPa, (8.0 ± 0.3) MPa•m^1/2, and (17.5 ± 0.2) GPa, respectively. SiAlON ceramics with high strength, high hardness and high toughness can be obtained with simultaneous addition of La₂O₃ and Al₂O₃ due to the acceleration of the anisotropic growth of α- and β-SiAlON grains, despite the decrease in the phase content of α-SiAlON.

Key words: α-SiAlON; in-situ toughening; microstructure; mechanical properties; La₂O₃