【作者】 王玉林；

【导师】 刘咏；

【作者基本信息】 中南大学 ， 材料学， 2011， 硕士

【摘要】 钛基复合材料以其高的比强度、比刚度、优异的耐磨性和抗高温特性而引起广泛的注意,近年来得到很快的发展。原位生成颗粒增强钛基复合材料具有各向同性,且易于成型,成本低廉,应用比较广泛。随着钛基复合材料的发展,根据实际应用中的各种需求,研究其高温氧化行为和耐磨性能越来越重要。本研究从颗粒增强相添加物的选择和含量、基体中金属元素和合金元素的选择这两方面对复合材料性能展开研究,采用粉末冶金法制备了原位生成TiC/Ti基复合材料,用UTM-3型摩擦磨损试验机和高温扩散炉对其在不同条件下的摩擦行为和在不同温度下的高温氧化行为进行了研究。利用X射线衍射(XRD)、扫描电镜(SEM)、能谱(EDX)等分析手段对材料的相组成和显微组织进行了分析。得到以下结论：1.金属碳化物粉、6A1-4V中间合金粉的添加量、Al/Sn/Zr金属粉末的添加以及金属碳化物的种类对TiC/Ti基复合材料的摩擦行为有显著的影响。Mo2C的添加,可以减少α-Ti的磨损量,提高其耐磨性。VC添加量较小时,可减少α-Ti的磨损量,当添加量达到12%时,磨损量反而升高,耐磨性变差。添加Mo2C的复合材料磨损量明显低于添加VC的复合材料。由于Sn, Al, Zr等金属与铁的粘着能大,使得粘着磨损现象加剧,故6A1-4V合金粉的添加量增加将导致复合材料磨损量增加,而添加铝、锡、锆粉的TMCs磨损量最大。2.TMCs的主要磨损机制为粘着磨损、磨粒磨损和氧化磨损,其耐磨性主要由基体的性质决定。与V相比,Mo对基体有更好的固溶强化作用,利于提高耐磨性。添加VC的钛基复合材料中,基体的韧性高,生成的TiC颗粒细小且弥散的分布,使得磨粒磨损加剧,甚至导致三体磨损产生。而在添加Mo2C的钛基复合材料中,生成的TiC颗粒相对较大且有偏聚现象,耐磨性较好。3相同条件下,添加Mo2C的钛基复合材料的抗氧化性明显优于添加VC的钛基复合材料。Ti+x%Mo2C钛基复合材料具有抛物线型氧化规律,不同添加量对氧化动力学曲线没有明显的影响。Ti+x%VC钛基复合材料具有近直线型氧化规律,随着添加量的增加和温度的升高,氧化程度加剧并最终出现氧化失效。Mo2C和6A1-4V中间合金粉同时添加的钛基复合材料具有抛物线-直线混合型氧化规律。而添加A1,Sn, Zr金属粉末的钛基复合材料具有近抛物线型氧化规律。4.添加物的种类对基体β-Ti相和TiC颗粒在氧化过程中的演化有重要影响。富Mo的β-Ti相在氧的作用下转变成α-Ti相,并且Mo也固溶于相应α-Ti相中,抑制了氧的扩散,提高了增强相颗粒的稳定性,有利于提高材料的抗氧化性。富V的β-Ti相氧化产物V2O5具有很强的挥发性,使得氧化层产生大量微裂纹,加速氧的扩散,为TiC颗粒的氧化提供有利条件。而且,V2O5和CO2可通过裂纹排出,使得氧化反应更容易进行,进一步降低了材料的抗氧化性。尽管存在能提高抗氧化性的Al和Mo2C,但V的添加易导致氧化层出现孔洞等缺陷,故添加6A1-4V中间合金粉的钛基复合材料其抗氧化性随着添加量的增加反而下降。锡、锆与铝配合起来使用更加有利于合金的热强性,此种金属粉末的添加可有效提高材料的抗氧化性。更多还原

【Abstract】 Titanium matrix composites have great specific strength, specific stiffness, wear resistance and high temperature resistance, which have been widely noticed and developed rapidly for recent years. In-situ particle reinforced titanium matrix composites are isotropous and easy to shape up, what is more, the cost is low. Therefore, the preparation method of in-situ synthesized is widly applied. With the development of the titanium matrix composites, studying the high temperature behavior and wear resistance of the TMCs is more and more important in the practical applications so as to satisfy different needs. This paper studies the oxidation behaviors of various TMCs at different temperatures by using high temperature diffusion furnace and wear behaviors of the TMCs on different conditions by using UTM-3 friction test machine, so as to make clear that how various additions and the addition amounts affect the properties of TiC/Ti matrix composites. The samples are made by powder metallurgy method (PMM). The phase compositions and microstructures are detected and analyzed by X-ray diffraction (XRD), energy spectrum and scanning electron microscope (EDX and SEM), respectively. The conclusions include:1. The wear behavior of TiC/Ti matrix composites is influenced by many factors, such as the addition of metallic carbide, the variety of metallic carbide, the addition amout of 6A1-4V powder and other metal powders (Al, Sn, Zr). The results show that Mo2C can reduce the mass loss of a-Ti and improve the wear resistance. When the VC addition amount is less, the mass loss decreases, however, when the addition amount is up to 12%, the mass loss increases. The wear resistance of the TMCs with Mo2C addition is better than that with VC addition. The adhension energy between Fe and other metals (Sn, Al, Zr) is great, which will aggravate the adhesive wear. Therefore, with the increasing addition amount of 6A1-4V, the mass loss increases, and the mass loss of the material with Sn, Al, Zr addition is the largest.2. The wear mechanisms of the TMCs are adhensive wear, abrasive wear and oxidation wear. The wear resistance is mainly up to the matrix. Comparing with V, Mo has better solid solution strengthening effect in the matrix, which can improve the wear resistance. For the sample with VC addition, the matrix toughness is good, and the well-dispersed TiC particle has small size, which can make the abrasive wear aggravate and even lead to three body wear. TiC particles have larger size and uneven dispersion in the TMCs with Mo2C addition, so the wear resistance is better.3. The TMCs with Mo2C addition have better oxidation resistance than that with VC addition. The oxidation kinetics curve of Ti+x%Mo2C is parabolic, which is not related to the addition amount. The oxidation kinetics curve of Ti+x%VC is linear. With the increasing VC addition amount and temperature, the oxidation resistance decreases. The TMCs with Mo2C and 6Al-4V addition have a complex rule, which is compounded by parabolic rule and linear rule. The oxidation kinetics curve of the TMCs with Al, Sn and Zr addition is nearly parabolic.4. The variety of the addion in the matrix has great influence on the oxidation behavior of theβ-Ti phase and TiC particle. Theβ-Ti, where Mo is abundant, transforms toα-Ti under the effect of the oxygen. Mo has solid solution strengthening effect on theα-Ti, which restrains the diffusion of the oxygen and increase the steability of the TiC. Therefore, the addition of Mo is beneficial for the oxidation resistance. V2O5, the oxidation product, is volatile, which will increase the microcracks in the oxidation layer and accelerate the diffusion of the oxygen. V2O5 and CO2 can be expelled through the flaws, and the oxidation reaction is easier to proceed. Therefore, theβ-Ti, where V is abundant, has bad oxidation resistance. Although there are Al and Mo2C, with the increasing addition amount, the oxidation resistance of the TMCs with 6A1-4V addition decreases for the increasing amount ofⅤ. The compound addition of Sn, Zr and Al is beneficial to the heat resistance, so the TMCs with these metal powders have good oxidation resistance.更多还原