Abstract: The influence of processing and microstructure on the mechanical properties of Sialon-based ceramics,
in-situ self-toughening induced by heat treatment and second-phase toughened, was investigated. Three kinds of Sialon-based ceramic materials were covered
in the research: 1. TiB_{( p)}, MoSi_{2( p)}, SiC_(p), and SiC_(w) second-phase reinforced Sialon materials; 2. α/β-double-phase-Sialon ceramics, using rare earth oxides Nd₂O₃,
Dy₂O₃, and Yb₂O₃ as sintering additives, 3. Sialon ceramics with elongated α-sialon grains. The experimental resules showed that
as to TiB_(p), MoSi_2(p), SiC_(p), and SiC_(w) second-phase reinforced Sialon materials, the toughening effect is mainly controlled by the bonding
between matrix and second-phase and the critical size of second-phase particles. In Nd₂O₃-, Dy₂O₃-, and Yb₂O₃-added Sialon
ceramics, Nd₂O₃ is a kind of effective sintering additive and Nd-Sialon possesses the highest K_1c value (7.0 MPa·m^1/2 due to the
elongated β-Sialon grains developed by heat treatment in order to induce in-situ self-toughening mechanism. Yb₂O₃ is not only an effective sintering additive, but also a useful
α-Sialon stabilizer, so Yb-Sialon is hard, with a highest Vickers hardness H_v10 of 18.0 GPa, because of the existing of
equiaxed α-Sialon grains in the samples. The action of Dy₂O₃ is between Nd₂O₃ and Yb₂O₃. The growth mechanism of elongated
α-sialon grains is declared to be the heterogeneous nucleation and anisotropic growth.

Key words: Sialon-based ceramics, second-phase toughening, in-situ toughening, microstructure, mechanical property