Effect of additive composition on mechanical properties of pressureless sintered silicon carbide ceramics sintered with alumina, aluminum nitride and yttria

• Published in: Metals and materials international 2015, 21(3), , pp.525-530
• Main Authors: Eom, Jung-Hye, Seo, Yu-Kwang, Kim, Young-Wook, Lee, Seoung-Jae
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Engineering Thermodynamics; Heat and Mass Transfer; Machines; Magnetic Materials; Magnetism; Manufacturing; Materials Science; Metallic Materials; Processes; Solid Mechanics; 재료공학
• ISSN: 1598-9623; 2005-4149
• DOI: 10.1007/s12540-015-4383-0

Silicon carbide (SiC) ceramics were pressureless sintered with 3 vol% Al 2 O 3 -Y 2 O 3 -AlN additives with the AlN/(Al 2 O 3 +AlN) molar ratios of 0-0.75 at 1850-2000 °C for 1 hr and the effects of additive composition (i.e., changes in the AlN/(Al 2 O 3 +AlN) molar ratio while maintaining constant Y 2 O 3 content) on the mechanical properties of the pressureless-sintered SiC ceramics were investigated. Self-reinforced microstructures consisting of relatively large platelet SiC grains and relatively small equiaxed grains have been obtained in all specimens when sintered at 1900 °C for 1 h in an argon atmosphere. The achievement of self-reinforced microstructures under such mild conditions (holding for 1 hr at 1900 °C) is caused by the beneficial effects of additive composition and the acceleration of the β→α phase transformation of SiC by seeding, i.e., the addition of 1 vol% α-SiC into β-SiC. The typical flexural strength and fracture toughness of the pressureless-sintered SiC ceramics with an AlN/(Al 2 O 3 +AlN) mole ratio of 0.5 were 433 MPa and 6.6 MPa·m 1/2 at room temperature, respectively.