【作者】 张全萍；

【导师】 许伯藩；

【作者基本信息】 武汉科技大学 ， 材料学， 2001， 硕士

【摘要】 无压自浸渗法是指在不借助任何外力作用下，把熔炼好的铝液，经精炼，调温后，浇入经过预热，含有增强体颗粒与助渗剂的混合体粉末中。在助渗剂的参与下，液态铝或其合金借助自身重力的作用，自动浸渗入粉末中制备颗粒增强铝基复合材料。其工艺设备简单，成本低，制备的颗粒增强铝基复合材料具有高强度和弹性模量及好的高温新能，与单一的铝合金相比，是一种在航天工业和汽车工业中有应用前途的材料。但采用无压自浸渗法制备SiCp颗粒增强铝基复合材料仍存在以下两个突出的问题：1．在1000℃以下，SiC颗粒与铝或铝合金之间浸润性差。2．SiC颗粒增强复合材料中界面反应生成的有害杂质相较多，对复合材料的性能的影响较大。可以通过添加Mg、Li等活泼的合金元素，对增强体颗粒进行表面预处理来改善润湿性。 本文通过研究制备SiCp／Al复合材料、SiCp／Al-Si复合材料的过程中，熔融铝液或铝硅合金液的浸渗行为、SiC-Al、SiC-Al-Si之间的界面反应、复合材料的机械性能、微观结构等，探讨了不同量的活性元素Mg、Si、Ce对SiC颗粒与熔融基体之间的润湿性及复合材料性能的影响。，结果表明：Mg可降低熔融Al液和Al-Si液的表面张力，改善了SiC-Al、SiC-Al-Si间的浸润性。Mg在SiCp／Al复合材料界面与SiC颗粒表面的氧化膜SiO₂及Al反应，在SiC颗粒与基体Al之间界面处生成MgAl₂O₄；Mg在SiCp／Al-Si复合材料中与SiC颗粒表面SiO₂氧化膜反应，在SiC颗粒与基体Al-Si之间的界面处生成MgO，因此Mg有效地抑制了脆性相Al₄C₃的生成。当Mg含量为1.0％时，对复合材料的力学性能和微观组织结构改善程度最大。另外发现Mg与空气中的氮气反应生成的MgN₂对SiC颗粒增强复合材料的浸润性也有改善作用。添加同等量的稀土Ce元素时，对SiCp／Al-Si复合材料浸润性的改善程度没有对SiCp／Al复合材料浸润性改善程度明显，因为Ce与Al-Si合金中的Si反应生成稳定的Ce₅Si₃类化合物，损失了一部分的稀土Ce。所以稀土Ce的添加量分别为0.3％和0.9％时，对SiCp／Al复合材料、SiCp／Al-Si复合 武汉科技大学硕士论文 摘 要 材料的力学性能和润湿性改善程度最大。St元素也可有效地降低AI．C。脆性 相的量，增加铝液的流动性，提高h 颗粒与基体之间的浸润性，对SICP八 复合材料的性能有明显的改善作用。更多还原

【Abstract】 The Pressureless Infiltration Technique means that the spontaneous infiltration of the refined molten Al or Al-Si alloy into the power bed , contains the filler reinforcement particle and K2TiP4, occurred at 900 to fabricate SiCp/Al or SiCp/Al-Si composites, without the aid of any externally applied pressure or vacuum, only by its gravity. The technique require simple process and equipment, so the cost is low, It’s a promising method for fabricating MMCs. The MMCs made by the method offer high strength and modulus as well as good high-temperature properties, when compared to corresponding monolithic alloys and they are promising materials for automotive and aerospace industry applications.However, the following two difficulties still exist: 1. Wetting between reinforcement SiCp and the molten metal is often poor when it is blow 1000’C; 2.During the processing, many phases of the interfacial reaction products have negative influence on the properties of the produced composites. The problems can be addressed, in part, through a strongly reactive alloying addition ,such as Mg, Li and so on, and through reinforcement coating .In this paper SiCp/Al composites and SiCp/Al-Si composites fabricated by the pressureless infiltration method . In order to found out the influence the different quantity of the reactive alloying addition Mg Si Ce on the wetting between SiCp and molten metal as well as the properties of MMCs , the behaviors of molten metal ,the mechanical properties, micro-structure and the interfacial reactions was investigated respectively .The results indicate that: the addition of Mg decreases the surface tension of molten Al and Al-Si alloy, reduce the solid/liquid interfacial energy and induce chemical reaction at the interface .so it improves wetting of Al and Al-Si metal and SiCp ceramic system .The most significant influence occurred at 1.0% Mg on both SiCp/Al composites and SiCp/Al-Si composites. The addition of Mg reactswith Al and SiO2 then form MgAl2O4 at the interface in the SiCp/Al composites; It reacts with SiO2 and produce MgO at the interface in SiCp/Al-Si composites, the good metal-ceramic bond is achieved. Mg can prevent the fragile AUC3 phase from producing, then the properties of the MMCs are improved. The addition of Ce can also improve the wetting between Al-Si-SiCp ceramic system. While it influent on the Al-SiCp ceramic system more effectively. Because the reactive alloying addition Ce react with Si in molten Al-Si and form stable compound CesSis .Therefore , when Ce is 0.3% and 0.9% can improve the wetting most significantly of Al-SiCp system and Al-Si-SiCp system respectively. Comparing the micro-structure and properties of SiCp/Al composites and SiCp/Al-Si composites ,we know that the addition of 11-13% Si can counteract the fragile Al4Cs phase obviously. At the same time Si causes significant changes to the viscosity of molten Al and Al-Si alloy and enhances wetting between SiCp ceramic and molten metal.更多还原