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

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