无压浸渗制备Si_3N_4/Al复合材料的界面反应研究

Study of Interface Reaction in the Si_3N_4/Al Composite Prepared by Pressureless Infiltration

研究S i3N4多孔预制体的表面氧化程度对无压浸渗制备S i3N4/A l复合材料界面反应以及复合材料性能的影响是复合材料优化设计的基础。不同氧化程度的S i3N4多孔预制体在相同的浸渗工艺下无压浸渗制得S i3N4/A l复合材料,利用EDS,XRD和洛氏硬度计分别测定陶瓷多孔预制体的成份,复合材料的相组成和硬度。结果表明:S i3N4/A l复合材料组成相包括A l,S i3N4,A lN以及少量的S i,Mg2S i,MgO,MgA l2O4;随着氧化程度增加,复合材料内A lN相减少,MgO含量增加,并逐渐出现MgA l2O4相;复合材料的硬度随预制体的氧化程度增加而线性下降;预制体的氧化造成S i3N4和A l之间的反应减弱是硬度下降的重要原因。

It is significant to study the relationship between the oxidation level of the Si3 N4 porous preform and the interface reaction for providing the base of optimizing designation of the Si3 N4/Al composite. The preforms with different oxidation level were pressurelessly infiltrated under the same processing conditions. Oxygen content of the preforms, phase constituents, and hardness of the composites were characterized by EDS, XRD instruments and Rockwell hardness tester respectively. The XRD results showed that the Si3 N4/Al composite contain AI,Si3N4 ,AlN and a small amount of Si ,Mg2Si ,MgO ,MgAl2O4. With the increasing oxidation level of preforms, the reaction product of AlN decreased remarkably and MgO increased. More MgAl2O4 were measured from the composite which preform presintered at the higher temperature of 1200℃. The hardness of composite went down with the increasing of the oxidation level of preform. It is an important reason for the reduction of the hardness of composites that the oxide over Si3N4 particles results in the decreasing of replacement reaction between Al-Mg melt and Si3 N4.