【作者】 刘佑铭；

【导师】 许伯藩；

【作者基本信息】 武汉科技大学 ， 金属材料及热处理， 2002， 硕士

【摘要】 金属基复合材料在六十年代开始有了较快的发展，成为了复合材料领域的新支，其中，铝基复合材料的发展尤为迅速，因为它具有重量轻、比强度高、剪切强度高、热膨胀系数低、高的弹性模量，良好的热稳定性、导热性能等一系列优点。制备金属基复合材料的工艺分为粉末冶金法、铸造法（铸造法细分为搅拌铸造法、原位接触反应法、液相浸渗法、共喷射沉积法）、反应机械合金化技术。其中原位复合工艺设备简单，基本上能克服其它工艺中通常出现的一系列问题，如基体与增强体浸润不良，增强体分布不均匀，特别是微小的（亚微米和纳米级）增强体极难进行复合等，作为一种具有突破性的新工艺方法而受到普遍的重视，并广泛开展了研究工作。TiC颗粒具有高硬度、高熔点、高模量等特性，作为增强体对提高复合材料的耐磨性和高温性能有显著的提高，因此TiC颗粒增强铝基复合材料成为金属基复合材料领域的热门课题。但是目前在原位反应时，除了所预计生成的增强体外，仍会生成其它副反应夹杂物（即脆性相Al₃Ti和Al₄C₃的生成），同时对增强体TiC颗粒的体积分数也难以精确控制，因而影响材料质量的稳定性。 本文采用在原位复合+铸造法制备TiC／Al基复合材料时以Mg和稀土氧化物CeO₂作为添加剂，研究稀土和镁对增强相TiC颗粒的形貌，生成量、复合材料的微观结构、机械性能的影响。 实验结果表明，TiC颗粒的生成过程是一个热动力学过程。加入适量的Mg（2wt％）可以抑制TiC／Al复合材料中的脆性相Al₃Ti的产生，生成仅含TiC的铝基复合材料；由于活化剂镁在体系中与石墨颗粒周围的氧化物、以及外来的氧反应放热，在熔体中形成微高温区，促进Al-Ti反应，同时，Al-Ti反应也是放热反应，因此体系中的内能急剧增大，促使Al₃Ti分解以及Ti朝C颗粒扩散，缩短反应的孕育时间。同时加镁后生成的TiC颗粒的扩散速率增大，因而增大了TiC颗粒的形核数，使生成的TiC颗粒更加细小弥散，在复合材料中的所占体积分数增大。 加入0.5wt％的稀土CeO₂增大了熔体的表面张力及流动性，从而在反应阶段增大Ti原子朝C颗粒的扩散速率，促使TiC颗粒生成，以及在反应完成后增大TiC颗粒朝熔体中扩散的速率，促使TiC颗粒的形核。稀土CeO₂净化铝熔体和颗粒的表面，改善了增强体与熔体的浸润性，提高复合材料的综合性能。 加入适量添加剂Mg和稀土CeO₂使原位TiC／Al，TiC／Al-Si复合材料的硬 武汉科技人学硕1：论义 度、咐磨性、抗拉强度、延伸率得到很大的提高。更多还原

【Abstract】 Metal matrix composite had begun to develop early in 1960s, and became one new branch in the field of composite. Among them, the aluminum based matrix developed especial quickly, because it has many merits compared with other metal, such as light weight, specific strength and shear strength, low coefficient of thermal expansion, high young’s modulus, better thermal stability and temperature conductivity. The technique of producing metal matrix composite include powder metallurgy, casting(including stirring casting process, in situ contact reaction process, liquid-phase metal infiltration process, co-spray deposition forming process), reaction mechanic alloying process. Among them, the equipment of in situ composition process required simply, and can basically overcame a series of question meted by the other technique, such as the poor wettability between the reinforced particle and metal matrix, reinforced particles aren’t distributed homogeneously, especially, the minute reinforced particles(such as sub-micron graded and nanometer graded) are difficultly compounded, and so on. As one new technique, it is attached important to many researchers, and is researched broadly. TiC particle possesses high hardness, wear-resisting property, high temperature stability, high melting point, high young’s modulus. As reinforced phase, it can remar Improve the wear-resisting property , strength and high temperature stability, and it become one popular research way. But during the process of in situ reaction, in addition to the reinforced phase, composite will exit the other by-product (such as fragility phase AlsTi and Al4C3), mean while, it is difficult to control the volume fraction of TiC particles accurately, and lead to poor stability of material property.During the producing TiC/Al matrix composite by in situ compounding+casting technique, this article added Mg and rare earth as additive. Article researched the effect of additive on the pattern and volume fraction of reinforced phase TiC particles, and the microstructure and mechanic property of composite.The result of experiment showed that the reaction between Ti and C is a thermodynamic course, when 2 wt% Mg is added to melt, it can restrain the formation of fragility phase Al3Ti, and gained Al matrix composite which contained TiC reinforced particles only. Because Mg reacts with the forms a micro-high temperature field around the oxide around the graphite particles and the oxygen gas which is brought by the immersion bell, and the reaction gives out a lot of heat energy, thusforms many high micro-fields in melt, which prompt the reaction between the Al and Ti. At the some time, the reaction between Ti and Al also is an exothermal reaction, so the inner energy is increased sharply which prompt Al3Ti to decompose and the diffusion rate of Ti toward graphite particles and the decrease the inoculation tune. At the same tune, the formed TiC diffuses toward melt with quicker speed rate. Al these can increase the nucleation rate, so the TiC particles become smaller and disperse more homogeneous, and the volume fraction of TiC is increased.When 0.5wt% rare earth CeO2 is added to melt, the surface tension of melt is decreased and fluidity is enhanced, accordingly it enhances the diffusion rate of Ti to C particles during the course of reaction and prompts the formation of TiC. During the latest course of reaction, the formed TiC diffuses to melt with quicker speed as the TiC/Al +Mg, and the nucleation rate is increased. Moreover, rare earth CeO2 can clean the melt and the face of reinforced particles and improve the wettability between the reinforced phase and melt and the property of material.Proper additive Mg and rare earth can improve the hardness, wear-resisting property tensile-strength, elongation percentage of TiC/Al, TiC/Al-Si composite.更多还原