【作者】 邓小燕；

【导师】 徐金城；

【作者基本信息】 兰州大学 ， 材料物理与化学， 2010， 博士

【摘要】 铝合金具有许多优良的性能,如比重小、导热导电性能好、抗氧化、耐腐蚀、塑性好,而且可加工性好,等等,在工业、民用等各个领域得到广泛应用。将具有高强度的铝合金作为基体,使它与硬度高、强度高和弹性模量大的陶瓷颗粒SiC、Al203、TiC,或者与具有固体润滑作用的碳纤维或石墨复合到一起,将得到非连续增强铝基复合材料。这类铝基复合材料的制备工艺灵活,而且可最大限度地综合发挥各组分材料的优势性能,使它既有铝合金高比强度,高导热,高阻尼等特点,同时又具有增强体高比模量,高耐磨,低膨胀和尺寸稳定性好等优异性能,是金属基复合材料中最具有广泛应用前景的一种新型材料,已经在航空航天、汽车和其它制造业作为结构材料得到了广泛的应用。本文研究了SiC颗粒和碳纤维的预处理方法,通过粉末冶金方法和时效热处理分别制备了SiCp／Al-Cu-Mg复合材料和Cf／Al-Cu复合材料,测试了它们的密度、硬度、抗拉强度和摩擦磨损性能,分析了机械合金化、增强相体积含量、载荷及其它因素对这两种复合材料的力学性能和摩擦磨损性能的影响,并探讨了复合材料的磨损机理。通过以上实验研究得到的主要结果如下。在SiCp／Al-Cu-Mg复合材料中,随着SiC颗粒体积分数的增加,复合材料的密度增大,硬度和抗拉强度呈现先增大后减小的规律,其中,9%SiCp／Al-Cu-Mg复合材料的力学性能最好。SiCp／Al-Cu-Mg复合材料的比磨损率随着SiC颗粒的含量增加而呈降低的趋势,其中以9%SiCp／Al-Cu-Mg和12%SiCp／Al-Cu-Mg复合材料的比磨损率最小。复合材料的比磨损率都明显低于其基体合金,表明SiCp／Al-Cu-Mg复合材料更耐磨。机械合金化使基体AlCuMg合金的抗拉强度明显提高,但对AlCuMg合金的密度、硬度、比磨损率和摩擦系数的影响不大。机械合金化使9%SiCp／Al-Cu-Mg复合材料的密度、硬度和抗拉强度明显提高,使其摩擦系数也增大,但对其比磨损率影响不大。载荷对复合材料的比磨损率影响不大,但使摩擦系数有所改变,比如,载荷越大,使9%SiCp／Al-Cu-Mg和12%SiCp／Al-Cu-Mg复合材料的摩擦系数越大。对于Cf／Al-Cu复合材料,随着碳纤维体积分数的增加,复合材料的密度减小,硬度和抗拉强度呈现先增大后减小的规律,其中6%Cf／Al-Cu复合材料的抗拉强度最高,而9%Cf／Al-Cu的硬度最高。Cf／Al-Cu复合材料的比磨损率随着碳纤维体积含量的增加呈先降低后增大的趋势,在Cf体积含量达6%左右时为最小值,而且Cf／Al-Cu复合材料的比磨损率都明显低于其基体合金。Cf／Al-Cu复合材料的摩擦系数随着碳纤维体积含量的增加呈降低的趋势。其中,基体AlCu合金和6%Cf／Al-Cu复合材料的摩擦系数相当,且为最大值,12%Cf／Al-Cu复合材料的摩擦系数最小。载荷对Cf／Al-Cu复合材料的比磨损率和摩擦系数的影响都不大,除了使12%Cf／Al-Cu复合材料的摩擦系数明显提高。SiCp／Al-Cu-Mg和Cf／Al-Cu复合材料的磨损机制均以粘着磨损为主。由于基体铝合金在磨损过程中容易被氧化,不可避免地存在有氧化磨损机制,而且Cf／Al-Cu复合材料因此在磨损过程中明显存在磨粒磨损机制。更多还原

【Abstract】 Aluminum alloys are widely used in industry and civil fields, because they have many excellent properties such as, light density, good thermal and electric conductivity, good oxidation resistance, good corrosion resistance and good plasticity, and easily to be machined. Using the different aluminum alloys with high strength as matrix, the discontinuously reinforced aluminum matrix composites are produced if they compound with the discontinuous materials such as, SiC, Al2O3, TiC particles with high hardness and elastic modulus or carbon fiber and graphite with solid lubricant effects. These discontinuous aluminum matrix composites can be made by variable manufacture technologies. In addition, they can furthest integrate their component properties advantages which make they have high strength, good thermal and electric conductivity and easily processing as the matrix aluminum alloys do. Besides, they may have high specific modulus, good wear resistance, and low expandability and dimension stability properties. Therefore, they are ones of advanced metal matrix composites, which have a most potentially wide application and have been used as structure materials in aerospace, automobile and other industries.In this paper, the pretreatment of SiC particles and carbon fibers are investigated, and SiCp/Al-Cu-Mg and Cf/Al-Cu composites are made by powder metallurgy and heat treatment, respectively. Their density, hardness, ultimate tensile strength and tribological properties are measured, the factors such as mechanical alloying technique, volume fraction of reinforcements and loads on their mechanical and wear properties are analyzed, and the wear mechanisms are discussed. The main results are therefore found as follows.To SiCp/Al-Cu-Mg composites, with the increase of the SiC particle volume fraction, their density increases, but their hardness and ultimate tensile strength increases first and then drops, as a result that 9%SiCp/Al-Cu-Mg composite has the optimize mechanical properties. The SiCp/Al-Cu-Mg composites have better wear resistance than the matrix alloy does. The wear rates of the composites are obviously lower than that of their matrix alloy, and they decrease with the increase of the SiC particle volume fraction.9%SiCp/Al-Cu-Mg and 12%SiCp/Al-Cu-Mg composites have the almost equal lowest wear rate values. The mechanical alloying technique improves the ultimate tensile strength of the AlCuMg matrix alloy, but it does not influence its density, hardness, wear rate and friction coefficient. On the other hand, the mechanical alloying technique enhances the density, hardness, ultimate tensile strength and friction coefficient of 9%SiCp/Al-Cu-Mg composite, but it does not influence its wear rate. The loads hardly affect the wear rate of SiCp/Al-Cu-Mg composites while somewhat change their friction coefficient, such as, the heavier load obviously raises that of 9%SiCp/Al-Cu-Mg and 12%SiCp/Al-Cu-Mg composites.To Cf/Al-Cu composites, their density drops with carbon fiber volume fraction (Vf) increasing, besides their hardness and ultimate tensile strength increases first and then decreases, of which 6% Cf/Al-Cu has the best ultimate tensile strength and the 9%Cf/Al-Cu has the best hardness. The wear rate of Cf/Al-Cu composites drops first and then increases with Vf of carbon fiber increasing, and the 6%Cf/Al-Cu composite has the lowest value. Furthermore, the wear rates of the composites are lower than that of the matrix alloy. The friction coefficient of Cf/Al-Cu composites drops with Vf of carbon fiber volume fraction augmenting. The AlCu matrix alloy and 6%Cf/Al-Cu composite have the equal maximum friction coefficient while the 12%Cf/Al-Cu composite has the minimum. The loads hardly affect the wear rates and friction coefficients of the composites, except that the heavier load enhances the friction coefficient of the 12%Cf/Al-Cu composite.The wear mechanism of SiCp/Al-Cu-Mg and Cf/Al-Cu composites is mainly adhesive mechanism. In additional, the oxidation mechanism inevitably exists because the aluminum matrix alloy is easily oxidized during the wearing process, resulting in that the abrasive mechanism exists in that of Cf/Al-Cu composites.更多还原