Abstract: To enhance their performance,SiC-MgAl₂O₄ composites were prepared using SiC particles as aggregates,MgAl₂O₄ fine powder,α-Al₂O₃ micropowder,Al powder and Si powder as the matrix,and phenolic resin as the binder,heat treating at 1 400,1 450,1 500,1 550 and 1 600 ℃ for 5 h in a nitrogen atmosphere.The growth process and crystal morphology of in-situ formed SiAlON reinforcing phases at different heat treatment temperatures,as well as their effects on the properties of the composites,were investigated.The results show that:(1)β-SiAlON is formed at 1 400-1 550 ℃; with the rising temperature,its content increases and its morphology becomes well-developed gradually,evolving into intact hexagonal columnar grains at 1 550 ℃;while β-SiAlON transforms into Mg-SiAlON gradually at 1 600 ℃;(2)the transformation from β-SiAlON to Mg-SiAlON is a phase transition process facilitated by Mg vapor originating from spinel decomposition and the high-temperature environment;(3)hexagonal columnar β-SiAlON effectively enhances the strength of the composites,whereas plate-like Mg-SiAlON contributes little to strength improvement,therefore,as the β-SiAlON content increases,the mechanical properties of the material gradually improve;however,after β-SiAlON transforms into Mg-SiAlON,the mechanical properties decrease;accordingly,the optimal heat treatment temperature is 1 550 ℃.

Key words: chromium-free, SiC-MgAl₂O₄ composites, SiAlON, heat treatment temperature, microstructure

摘要： 为提升SiC-MgAl₂O₄复合耐火材料的性能,以SiC颗粒为骨料,MgAl₂O₄细粉、α-Al₂O₃微粉、Al粉、Si粉为基质,热固性酚醛树脂为结合剂,在氮气气氛下经1 400、1 450、1 500、1 550、1 600 ℃保温5 h热处理制备了SiC-MgAl₂O₄复合材料。研究了不同热处理温度下原位生成的SiAlON增强相的生长过程、晶体形貌对该材料性能的影响。结果表明:1)1 400~1 550 ℃范围内,材料中生成β-SiAlON,随热处理温度的升高,β-SiAlON含量增多,形貌逐渐完整,1 550 ℃时表现为完整的六方柱状形貌;1 600 ℃时,β-SiAlON逐渐向Mg-SiAlON转化。2)β-SiAlON向Mg-SiAlON的转化过程是相变过程,尖晶石分解产生的Mg蒸气以及高温环境为该相变过程提供了条件。3)六方柱状的β-SiAlON能有效提升材料的强度,而片状的Mg-SiAlON对材料强度的提升作用较弱,因此,随β-SiAlON含量的增加,材料力学性能逐渐增大,当β-SiAlON转化为Mg-SiAlON后,材料的力学性能降低,最佳的热处理温度为1 550 ℃。

关键词: 无铬化, SiC-MgAl₂O₄复合材料, SiAlON, 热处理温度, 显微形貌