resumo
By applying SPS technique, new Yb alpha-SiAlON ceramics in situ toughened by rod-like grains were prepared at a relatively low temperature of 1600 degrees C, with combustion synthesized seed crystals added. The effects of sintering temperature, heating rate, and the addition of seed crystals on the densification process, phase transformation, microstructure development, and mechanical properties of the samples were discussed in detail. The experimental results showed that Yb alpha-SiAlON ceramics could be almost fully densified quickly by SPS, and the fast heating rate was helpful to reduce the amount of intermediate phases. Higher sintering temperature and appropriate holding time were beneficial to the promotion of phase transformation and grain growth. It was also demonstrated that the added seed crystals played an important role in enhancing the phase transformation and facilitating the growth of rod-like grains. Being toughened by the rod-like grains via the mechanisms such as grain pull-out and debonding, the fracture toughness of as-sintered Yb alpha-SiAlON ceramics with additive seed crystals was remarkably improved. (c) 2005 Elsevier B.V All rights reserved.
palavras-chave
AL-O-N; SILICON-NITRIDE; ALPHA'-SIALON CERAMICS; PHASE-RELATIONSHIPS; FRACTURE-TOUGHNESS; MICROSTRUCTURE; ALPHA-SI3N4; GROWTH
categoria
Science & Technology - Other Topics; Materials Science; Metallurgy & Metallurgical Engineering
autores
Liu, GH; Chen, KX; Zhou, H; Guo, J; Pereira, C; Ferreira, JMF
nossos autores
