TiAl基陶瓷复合材料的研究现状

TiAl金属问化合物经过十几年的研究,以其低密度、高模量和优异的高温强度、抗蠕变、抗氧化和阻燃性能而被公认为最具有发展潜力的高温结构材料.但由于其本身所固有的较低室温塑性和韧性,限制了其实际应用.TiAl基复合材料在保持TiAl金属间化合物诸多优良性能的同时,通过引入不同的陶瓷增强体,进一步提高了材料的高温强度、弹性模量、蠕变性能.本文对各种TiAl基陶瓷复合材料的主要研究现状进行了综述,重点阐述了不同TiAl基陶瓷复合材料的制备工艺和性能特点.     

原位合成Al6．1 Cu1．2 Ti2．7／Al2O3／TiAl复合材料及热力学分析

采用真空热压烧结方法在Ti—Al—CuO体系下原位合成了Al6.1 Cu1.2 Ti2、Al2O3物相共同增强的TiAl基复合材料。通过DSC,XRD以及相关热力学计算研究了热压反应过程。结果表明：Al在高温熔化后对Ti、CuO颗粒润湿并发生反应,Ti颗粒表层形成中间产物TiaAly,在富Ti区生成稳定TiAl相;CuO颗粒表层由于Al-CuO置换反应的发生,生成稳定的Al2O3相和活度较高的Cu单质,一定条件下TiaAly与Cu反应形成Al6.1Cu1.2Ti2.7三元相。     

Al2O3／TiAl复合材料的制备与性能研究

采用热压烧结法制备Al2O3／TiAl复合材料,研究了不同Al2O3体积分数对Al2O3／TiAl复合材料的相对密度、弯曲强度、断裂韧性以及耐磨性的影响。研究结果表明,掺入20％Al2O3时,复合材料的相对密度达到最小,随着烧结温度的不断升高,Al2O3／TiAl复合材料的相对密度不断增加。当Al2O3含量为15％时,弯曲强度与断裂韧性达到最佳,其值分别为865．9Mpa和17．60MPam^1/2。随Al2O3体积分数的增加,Al2O3／TiAl复合材料的摩擦系数不断增加,而磨损失重则呈先降低后增大的变化趋势,当Al2O3含量为15％时,在不同载荷作用下,材料的磨损失重均最小。     

单向纤维增强SiC基复合材料界面微结构的研究

采用先驱体浸流法制备了３种不同纤维增强的ＳｉＣ基复合材料,观察,分析了材料的微观结构,界面成分以及相应的材料性能。研究发现：在制备过程中Ｓｉ和Ｏ会逐渐从基体扩散到纤维中,并导致纤维劣的化,Ｍ４０ＪＢ碳纤维受损最严重,所制备材料性能最差;采用Ｈｉ－Ｎｉｃａｌｏｎ纤维增强的ＳｉＣ基复合材料具有最佳的性能,单向板弯曲强度达到７０３．６ＭＰａ,断裂韧性达到２３．１ＭＰａ．ｍ＾１／２。     

碳系水泥基复合材料的研究进展

本文介绍了国内外水泥基复合材料的研究进展,重点对水泥基导电复合材料、水泥基电磁屏蔽复合材料和水泥基压电机敏复合材料,如导电性能、磁性能、屏蔽性能、压电性能等材料的组成、特性及发展状况进行了综述.     

对提高树脂基复合材料某些力学性能的探讨

提要本文对复合材料破坏机理作了分析,得知若要防止复合材料低应力开裂,提高复合材料的强度,必须寻求在外力作用下基体材料体积增量最小的途径;寻求增加基体材料延伸率以及基体材料与增强材料最佳匹配关系的途径,为此,本文介绍了所做的相应实验,并给出了实验结果和提高某些复合材料力学性能的几点建议。     

助熔剂对原位转化碳纤维增韧陶瓷基复合材料性能的影响

本文以聚丙烯腈(PAN)预氧化纤维为先驱体,以氧化铝为主要原料,添加SiO2-MgO-CaO三系助熔剂,采用真空热压烧结法制备了原位转化碳纤维增韧氧化铝复合材料.主要探讨不同助熔剂添加量对复合材料微观结构和各项性能指标的影响.以体积密度、显微硬度和断裂韧性等性能指标为主要评价标准选择最佳的助熔剂添加量.并研究了原位转化碳纤维增韧氧化铝陶瓷的摩擦磨损行为与机制以及力学性能和微观结构对摩擦磨损特性的影响.结果表明:当助熔剂含量为3vol％时,复合材料的综合性能最优,此时体积密度为3.72 g·cm-3,显微硬度为1624 HV,断裂韧性为10.6 MPa·m1/2.在室温干摩擦条件下,复合材料的磨损率随着助熔剂含量的增加呈先升高后降低趋势.室温下原位转化碳纤维增韧氧化铝基复合材料的磨损机制以脆性剥落为主,并伴有疲劳磨损.     

树脂基复合材料的上限工作温度

本文讨论了表征树脂基复合材料上限工作温度的几种方法,认为根据固化温度或通过测定玻璃化转变温度（Tg）确定上限工作温度,很难给出可靠、准确的结果,采用经过条件处理后的力学性能测试方法,能很好的模拟实际工作条件,得出较测定Tg更有用的结果。     

TiAl／Zro2复合材料的制备与性能研究

研究了采用高能球磨工艺与热压烧结方法制备的TiAl／ZrO2陶瓷基复合材料的工艺条件、力学性能和微观结构。结果表明：TiAl质量分数为40％时,材料的致密度、维氏硬度、室温抗弯强度、断裂韧性分别达99％、13．7GPa、261．2MPa、3．2MPa·m1/2。大量穿晶断裂导致复合材料韧性较低。     

2维C/SiC复合材料的拉伸损伤演变过程和微观结构特征

通过单向拉伸和分段式加载-卸载实验,研究了二维编织C/SiC复合材料的宏观力学特性和损伤的变化过程.用扫描电镜对样品进行微观结构分析,并监测了载荷作用下复合材料的声发射行为.结果表明:在拉伸应力低于50MPa时,复合材料的应力-应变为线弹性;随着应力的增加,材料模量减小,非弹性应变变大,复合材料的应力-应变行为表现为非线性直至断裂.复合材料的平均断裂强度和断裂应变分别为23426MPa和0.6%.拉伸破坏损伤表现为:基体开裂,横向纤维束开裂,界面层脱粘,纤维断裂,层间剥离和纤维束断裂.损伤累积后最终导致复合材料交叉编织节点处纤维束逐层断裂和拔出,形成斜口断裂和平口断裂.     

原位(In-stiu)反应合成技术在制备金属基复合材料中的应用

综述了几种主要的原位反应合成技术，包括：XD^TM技术，Lanxide技术，VLS技术，反应喷射沉积技术，反应机械化技术和SHS技术，以及这些技术在金属复合材料制备中的应用，对各种技术的优缺点分别进行讨论，并指出了今后 的发展趋势。     

三元层状Ti2AlC陶瓷强化TiAl基复合材料的研究

三元层状Ti2AlC陶瓷作为H相的典型代表,兼具陶瓷和金属的优点,在TiAl基中引入部分Ti2AlC,制备的TiAl/Ti2AlC复合材料,兼具两者的优越性。简单介绍了Ti2AlC陶瓷的结构及其特性,同时叙述了其在制备TiAl基复合材料方面的研究进展,最后总结了其强化机制。     

硫化铜纳米颗粒的原位合成及摩擦学性能

采用原位合成的方法合成了硫化铜纳米微粒,通过静置及高低速离心测试,证明硫化铜纳米微粒在基础油石蜡中具有良好的分散稳定性。TEM研究证明合成的纳米颗粒粒径约为20 nm。通过FT-IR表征合成样品,发现油酸分子-COOH部分和硫化铜表面发生了化学性吸附,增强了硫化铜纳米微粒在基础油中的油溶性。用高速环-块磨损机考察了含硫化铜颗粒的基础油的摩擦学性能,发现添加有油酸修饰的硫化铜纳米颗粒有显著的抗磨减摩效果。     

Simulated Environments Testing System for Advanced Ceramic Matrix Composites

The present work aims toward the application of an innovative methodology for testing the environmental performance of advanced ceramic matrix composites in the presence of combined mechanical, thermal, and environmental applied conditions. To obtain a comprehensive understanding of how a composite might perform in certain application environments, a newly developed environmental performance testing platform, which includes simulated equivalent environments system (ES) and a wind tunnel environments system (WS), is proposed. A multiplication factor of 10.8 between the ES and WS at 1300°C has been obtained tentatively.     

Matrix Cracking in Ceramic-Matrix Composites

Matrix cracking in ceramic-matrix composites with unbonded frictional interface has been studied using fracture mechanics theory. The critical stress for extension of a fiber-bridged crack has been analyzed using the stress-intensity approach. The analysis uses a new shear-lag formulation of the crack-closure traction applied by the bridging fibers based on the assumption of a constant sliding friction stress over the sliding length of the fiber-matrix interface. The new formulation satisfies two required limiting conditions: (a) when the stress in the bridging fiber approaches the far-field applied stress, the crack-opening displacement approaches a steady-state upper limit that is in agreement with the previous formulations; and (b) in the limit of zero crack opening, the stress in the bridging fiber approaches the far-field fiber stress. This lower limit of the bridging stress is distinctly different from the previous formulations. For all other conditions, the closure traction is a function of the far-field applied stress in addition to the local crack-opening displacement, the interfacial sliding friction stress, and the material properties. Numerical calculations using the stress-intensity approach indicate that the critical stress for crack extension decreases with increasing crack length and approaches a constant steady-state value for large cracks. The steady-state matrix-cracking stress agrees with a steady-state energy balance analysis applied to the continuum model, but it is slightly less than the matrix-cracking stress predicted by such theories of steady-state cracking as that of Aveston, Cooper, and Kelly. The origin of this difference and a method for reconciliation of the two theoretical approaches are discussed.     

Fiber-Reinforced Diamond Matrix Composites

The feasibility of fiber-reinforced diamond matrix composites was examined. For this purpose, monofilament composite specimens were fabricated using SiC fibers. The diamond was deposited onto the fibers using plasmae-enhanced chemical vapor deposition. The mechanical properties of the composite were characterized using uniaxial tensile tests. The specimens exhibited multiple matrix cracking, followed by fiber fracture and fiber pullout. The measurements were used to obtain an estimate of the interface sliding stress and the in-situ fiber strength.     

等离子体反应合成铁铝尖晶石基复合材料

用喷雾造粒工艺制备了Fe2O3–Al复合粉体,通过等离子喷涂工艺制备出FeAl2O4基复合材料。对Fe2O3–Al复合粉颗粒在等离子体焰流内的状态变化、反应动力学、反应产物和急冷后材料的组织结构进行研究。结果表明：Fe2O3–Al复合粉颗粒在沉积前的温度为3 274.5℃,速率为179 m/s,主要反应产物为Fe–Al...     

Notch Effects in Carbon Matrix Composites

The tensile properties of various carbon matrix composites, reinforced with C and SiC fibers, have been evaluated. The objective is to assess mechanics procedures for characterizing the influence of holes and notches. Interpretation has been attempted using large-scale bridging mechanics, with linear elastic fracture mechanics as one limit and notch insensitivity as the other. Important differences between the materials, associated primarily with the fiber/matrix interfaces and the in-plane shear strength, have been identified and attempts made to rationalize these differences.     

Lanxide陶瓷基复合材料的研究进展

Lanxide熔融金属直接氧化技术是一种新型的复合材料制备技术,通过用预制体(颗粒、晶须、纤维等)增强所制备的复合材料具有高的体积稳定性、断裂韧性和强度,是目前材料科学领域的热点之一.本文就Lanxide技术及陶瓷基复合材料近年来的最新发展进行了概述.