【作者】 马洪涛；

【导师】 尹衍升；

【作者基本信息】 山东大学 ， 材料学， 2005， 博士

【摘要】 随着汽车工业的发展,特别是汽车向高速化和重载化发展的趋势,对摩擦材料提出了越来越高的要求。多年来,国内外对摩擦材料进行了广泛的研究,主要形成了有机合成摩擦材料、粉末冶金摩擦材料和碳/碳复合摩擦材料为主的体系。本文针对已有体系中的材料在使用中的某些缺陷,查阅、分析了大量国内外相关文献,考虑到Fe₃Al金属间化合物密度低,制造成本低,有良好的导热性能,特别是受Fe—Al金属间化合物特有的多键态结构带来的耐高温、抗氧化和耐腐蚀性能的启发,在国内首次选用Fe₃Al作为基体材料研制开发了Fe₃Al基复合摩擦材料,并获得初步成功。论文涉及材料学、热力学、摩擦学等诸多方面,研究内容富有创新性。 本文针对以下几个方面进行了研究:一、用球磨机械合金化工艺制备了Fe₃Al粉体材料,并对Fe₃Al的形成过程和机理进行了研究。也对粉体的制备工艺和随后的热处理过程的必要性,进行了研究,并借用XRD、TEM、SEM、DSC等现代化的测试手段,对Fe₃Al形成过程的组织结构演变及Fe₃Al粉体的形貌进行了表征和测试。二、在系统分析欲制备的摩擦材料结构和性能的基础上,优化选择了合适的摩擦阻元和润滑组元作为摩擦性能调节剂。分析计算了组元间的相容性,根据物理和化学相容原理,初步设计了新型摩擦材料配方,对它们进行混料。随后对其烧结工艺进行了优化,对其烧结原理进行了探讨。三、对制备的材料的性能和结构进行了研究,分析了烧结材料的相组成和界面结合方式。四、对制备的Fe₃Al摩擦材料进行了力学性能测试,着重测试其不同工况条件和不同组元含量下材料的摩擦性能和磨损机理。五、对制备的Fe₃Al基复合摩擦材料和传统的铁基摩擦材料进行摩擦性能对比试验,分析它们不同的磨损机制。并测试它们的抗氧化和耐腐蚀性能,研究了Fe₃Al基复合材料的抗氧化原理。六。对研制的Fe₃Al基复合材料进行了模拟制动试验,考察了其制动性能和摩擦磨损性能。 针对以上研究过程,得出如下的主要研究结论: 一、通过球磨机械合金化工艺,能够使Al、Fe元素粉末在球磨过程中使Al原子逐渐溶于Fe中形成无序α—Fe（Al）过饱和固溶体,通过随后在750℃更多还原

【Abstract】 With the rapid development of automobile industry, especially the trend towards higher speed and heavier load for the automobiles, there is an increasingly high standard for friction materials. Careful research on friction materials has been done around the word for many years and the present system include materials mainly consist of polymer matrix, powder metallurgy friction materials and C/C friction materials. In order to overcome the defects of the traditional materials, correlative literature both domestic and overseas was consulted and analyzed. With its structure of much bond, lower cost, much lower density, better thermal conductivity and what’ s more important, its performance of resistance to high temperature, oxidation and corrosion brought by its unique structure, Fe₃Al intermetallics was chosen as the basic materials. This thesis has for the first time in China put forward a theory that friction materials were made by developing a new matrix named Fe₃Al-base. The composite has been made successfully. The study covers areas such as material science, thermodynamics, tribology and some other disciplines and the research is creative as well as systematical.The following has been systematically and emphatically investigated. First, Fe₃Al powder was prepared by milling mechanical alloying technology. Relevant studies were conducted on its formation process and mechanism, its technology process and the necessity to apply annealing treatment. The structural evolution of Fe-Al elemental during mechanical alloying process, and the shape of Fe₃Al particle have been investigated and tested by means of XRD, TEM, SEM and DSC. Second, based on systematic analysis of the structure and performance of materials to prepare, appropriate friction components and lubrication components were optimized as the added ingredient. Further analysis and calculation were done on thephysical and chemical compatibility between them. A new friction material formula was then developed and these components were mixed. Subsequently sintering technology was optimized and sintering theory was explored. Third, the structure and performance of friction materials prepared were studied, and bond and structure of interface were studied in detail. Forth, mechanics performance of friction materials prepared was tested, and on the condition of different testing condition and changing content of components, friction capability and wear mechanism of material were studied. Fifth, comparative experiments on friction capacity of FeaAl and Fe-base friction materials were carried out and their wear mechanism was studied. Studies was also done on their capacity of resistance to oxidation and corrosion and the mechanism of resistance to oxidation of FesAl was discussed. Sixth, its simulating braking test was made, and its braking characteristic and friction wear capability were studied too.The major conclusions drawn from the research are as follows. Depending on milling mechanical alloying technology, with the increase in milling time, Al atom can dissolve crystal lattice of Fe, and form disordered a - Fe solid solution. During annealing at 750°C .through Al atom order rearrangement and removing of APS domains, the lower B2 ordered and higher ordered structure were obtained. Making use of the technology, relatively inexpensive Fe and Al powder were made into FeijAl-base to prepare Fe3Al-base composite.During the experiment, the raw material components, such as Cu powder, AI2O3, graphite, MoS2 etc, manifested good physical and chemical compatibility. Therefore, they can be mixed altogether and sintered. The result proved that Cu powder played an important role in strengthening sintering capacity. Having taken into account most factors of sintering process, an optimized Fe3Al base friction material technology of sintering composite came into being: sintering pressure of l(M5MPa, sinteringtemperature of 10504100°C and holding time 30min .The investigations into the bond component and the structure of interface of Fe3Al-base friction materials revealed the following. 1. Fe3Al-base composite sintered consist of a majority of B2 and a few DO, structure form. 2. In the process of sintering composite, many A12O3 particles were produced. Furthermore, Cu functions as mucilage glue and felted components together. Cu dissociated with other components. 3. The composite sintered presented favorable interface in the course of components and no obvious reaction products emerged. The integration of graphite with other components in the interface was weaker and therefore it was common that micro-crackle came into being here and extended. As result of it, the material was destroyed. However in the experiment, graphite atom diffused into base in the interface and this can improve feebleness bonding strength between graphite and components.The size of Fe^Al particles affected friction capability of composite, but too small particles produced much crystal particle boundary, and more defects, which went against the improvement of friction capacity.Depending on various reinforcing mechanism, such as solid solution, precipitation hardening, etc, Cu can reinforce Fe3Al base friction materials in the course of friction experiment. Because of physical and chemical action, Cu shifted from dissociating state to the surface and formed friction layer, which changed wear mechanism and improved friction capacity. The addition of Cu not only changed the composite wear mechanism, but also transformed the composite from particle abrasion brought by brittleness rupture to a mixed abrasion of particle abrasion brought by plasticity fluxion and slight adhesion abrasion. A high Cu content made the composite exhibit heavy adhesion abrasion while appropriate Cu content can reduce wear rate on the condition of high-speed sliding test.Because of its unfavorable interface bonding with other bond,Graphite decreased mechanics capacity. In the course of friction test, graphite mixed a little Cu can shift into lubricating layer with a low graphite content, composite exhibited slight adhesion abrasion; while with a high graphite content, because of much boundary limitation, mechanics capacity declined sharply. When graphite slice cracked because of cutting to form much graphite particle, wear performance is transformed to heavier particle abrasion with brittle split of materials. Due to better compatibility between MoS2 and mental particles, appropriate MoS2 content improved impact strength of composite. With too much MoS2, conglomeration of MoS2 declined mechanics capacity and friction wear performance, and to be specific, it resulted in severe adhesion abrasion. The research also proved that appropriate hole density can detain worn scraps and decrease wear rate. In the experiment, the friction coefficient of Fe3Al-based friction materials is 0. 5 or so and the average wear rate is 0.45-0. 1X10"5 mm’NV.Fe3Al-base friction materials manifested excellent resistance to heat impact and high temperature oxidation. In a relatively wide range of temperature, it had no micro crackle and no oxidation layer warping. Compared with Fe-based friction, Fe3Al-base friction materials exhibited excellent resistance to oxidation between 800°C and 1000°C. This could be attributed to the formation and protection of dense and continuous A12O3 film on the surface Fe3Al-base particulate. For FesAl-base friction materials, in the process of friction test, oxidation phenomena mainly happened on the surface of composite, and it became more and more unconspicuous from outside to inside. The main reason for the great enhancement of its resistance to oxidation lies in the formation, accumulation and film formation particles during the oxidation.The simulation brake test showed that Fe3Al-base friction braking sample braked with good stability, relatively invariable frictioncoefficient and lower wear rate. Friction test manifested it had no obvious friction coefficient decline due to temperature variation. It was also found that, in the process of friction, a layer came into being that consisted of graphite and Cu, the same as the result of M-2000 test. Braking test also proved that wear mechanism of braking sample of composite was particle abrasion, oxidation abrasion and adhesion abrasion, and that coincided with the preceding tests, too.Braking test showed that Fe^l-base friction materials had no conglutination and scrape with the counterpart and the composite can avoid the adhesion to cast iron material.To sum up, the thesis developed Fe3Al-base friction materials, and testified the feasibility of the formula. The experiment tested its mechanics capacity and probed its wear mechanism. The experiment not only explored the effects of other components its friction capacity, but also tested and simulated its friction capacity in complicated working conditions. It is testified that its capability of anti-oxidation and anti - corroding excelled one of Fe-base friction material. Braking test found that the material exhibited excellent braking performance, and possessed great potential in its development as a new friction braking material.更多还原