高体积分数SiC_p/Al复合材料表面粉化的原因

Surface Pulverization Cause of High Volume Fraction SiC_p/Al Composites

在850℃下,分别用纯铝熔体或硅质量分数为5%,12.5%,20%的铝硅合金熔体浸渗反应烧结碳化硅(RBSiC)坯体,获得硅含量不同的高体积分数SiC_p/Al复合材料;该复合材料在空气中长时间放置后表面粉化,采用扫描电镜、X射线衍射仪、X射线能谱仪等分析了复合材料及其粉化后粉末的组织形貌及成分,并分析其粉化原因。结果表明:在空气中静置两个月后,硅含量低的复合材料(原料中硅质量分数为0,5%)表面形成大量粉末,硅含量高的复合材料表面则不会粉化,粉末主要为棒状和片状Al(OH)_3;复合材料制备过程中由于硅含量不足产生了碳化铝,碳化铝在空气中水解导致粉化。

Reaction bonded silicon carbide （RBSiC） green body was separately immersed in aluminum melt and Al-Si alloy melt with silicon mass fraction of 5%, 12.5% and 20% respectively at 850 ℃, and then a series of high volume fraction SiCp/Al composites with various silicon contents were prepared. The surface pulverization of the composite after standing in air for a long period was observed, and the mierostructures, morphology and composition of the composite and its powders were studied by scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy. The reason for pulverization was also analyzed. The results show that after standing in air for two months, plenty of powders formed at the surface of the SiCp/Al composites with a relatively low silicon content （silicon mass fraction of 0 and 5% in raw materials）, but the pulverization at the surface of the composites with a relatively high silicon content was prevented. The powders mainly consisted of long rod-like and tabular-like AI（OH）3. Aluminum carbide was generated during the preparation of the composite due to insufficient silicon content and then hydrolyzed in the air, resulting in the pulverization.