熔体浸渍技术制备SiC_p/AlN复合材料

PREPARATION OF SiC_p/AlN COMPOSITE MATERIALS BY MELT INFILTRATION PROCESS

采用熔体浸渍技术 ,研究了在高纯氮气氛下AlMg Si合金反应浸渍碳化硅预形体制备SiCp/AlN复合材料。借助XRD ,SEM /EDS ,EMPA等测试手段检测了产物的物相组成 ,观察了材料的微观形貌 ,并对复合材料微区成分进行了分析。结果表明 :12 0 0℃下 ,在氮气气氛中用AlMgSi合金反应浸渍碳化硅形成了SiCp/AlN复合材料。在氮化温度下 ,AlMgSi合金中的Mg元素极易蒸发 ,与气氛中的微量氧发生反应 ,起到深脱氧作用 ,而Si元素的存在使AlSi熔体容易浸渍渗透进入SiC预形体中 ,同时氮化反应生成AlN ,形成了以AlN/Si为三维骨架 ,SiC呈孤岛状结构的SiCp/AlN复合材料。生长前沿氮化铝以胞状方式生长 ,胞内由呈放射状生长排列的柱状晶氮化铝构成 ,柱晶之间有大量的通道间隙 ,Si元素在胞内呈不均匀分布 ,胞边缘部分的硅含量明显高于胞中心部分 。

SiCp/AlN composite materials can be prepared by melt infiltration of Al-Mg-Si alloy into SiC preform in high pure N2 atmosphere. The phase compositions, morphology and micro-zone analysis of nitridation products were determined and observed by using XRD, SEM/EDS and EMPA. The results indicate that SiCp/AlN composite materials can be produced in such a melt infiltration process at 1200°C. For Al-Mg-Si alloy, Mg element easily evaporates and reacts with a micro amount of O2 in the N2 atmosphere to guarantee the low partial pressure of O2. Meanwhile, Si element can improve the wet ability of Al-Si melt on SiC particles. In such a case, alloy melt can easily penetrate into SiC preform and be directly nitrided to produce SiCp/AlN composite materials where AlN is continuous bonding phase. The AlN grown in the forward position is in the nodules form. In the nodules, AlN grains like a star like morphology of pillar-grains are arranged from the center to the edge. Between the pillar-grains, many micro-channels are located. EMPA shows that the distribution of Si element is much more at the edge of the nodular AlN than at its center, which is related to the growth mechanism of AlN.