SiC_p/Cu梯度复合材料热疲劳性能研究

采用粉末冶金方法制备了4种SiC颗粒呈渐变分布的梯度复合材料,应用扫描电子显微镜、X射线衍射仪、自动显微硬度计等,研究了梯度复合材料的显微组织、硬度分布和热疲劳性能。结果表明,SiCp/Cu梯度复合材料基体连续,梯度层过渡均匀,显微组织及硬度呈梯度分布;梯度复合材料的SiC颗粒渐变过渡越均匀,梯度复合材料抗热疲劳性能越好。     

原位生成TiC_P/Fe表面梯度复合材料组织及形成机理研究

利用铸造-热处理工艺原位反应生成了TiC颗粒增强铁基表面梯度复合材料,对该复合材料的组织进行了研究,并深刻剖析了该复合材料组织的形成机理。结果表明:原位合成的TiC增强表面梯度复合材料大致分为三层;每层之间最大的区别是生成的TiC颗粒的大小及形状不同。远离基体侧的反应层接近于大块状的TiC,显然是颗粒基本上没有扩散;反应层与基体结合界面良好、无间隙,结合层TiC颗粒平均大小为2～4μm。因此,各梯度层TiC颗粒的大小决定了此种复合材料的不同层具有不同的硬度、冲击性能、抗拉强度和耐磨性等。     

SiC_P/Cu梯度复合材料的制备及性能研究

采用粉末冶金方法制备了SiCP/Cu均质复合材料及梯度复合材料,并对复合材料的显微组织、硬度、导电率和耐磨性进行了研究。结果表明:均质复合材料中SiC颗粒含量越多,导电率越小,耐磨性越好;梯度复合材料基体连续,组织及硬度呈梯度分布且其耐磨性优于基体Cu材料;磨损机理是微切削磨损和磨粒磨损的复合作用。     

SiC颗粒增强铝基梯度复合材料的制备与性能

采用粉末冶金法制备了SiC颗粒增强铝基梯度复合材料（FGMMC），研究了该梯度复合材料的微观组织和力学性能，对FGMMC的显微组织观察表明，由于铝基体熔合成一体，因此层间没有明显的界面，具有基体的连续性，尽管基体是连续的，但是当疲劳裂纹从高SiC含量层向低SiC含量层扩展时，在过渡区发生延滞现象，通过断口和裂纹扩展路径的分析解释了此延滞现象。     

热处理对SiCp／ZL109复合材料机械性能的物理性能的影响

试验分析了不同热处理方法对ＳｉＣｐ／ＺＬ１０９复合材料机械性能和物理性能的影响；通过金相和透射电镜分析研究了其热处理强化机理，结果表明，Ｔ６热处理可大幅度提高复合材料的强度；Ｔ４热处理在提高强度的同时可增加复合材料的延伸率，复合材料强度的提高是由于ＳｉＣｐ的均匀分布和ＳｉＣｐ与Ａｌ基体热膨胀系数差导致的高密度位错产生的。     

梯度复合材料活塞的挤压铸造研究

陶瓷梯度增强铝基复合材料是发动机活塞的理想增强材料。采用挤压铸造法制造出梯度复合材料活塞,对梯度 复合材料的层间结合的显微组织进行了观察,发现复合材料之间、复合材料与基体之间的结合情况非常令人满意。采用 ANSYS有限元分析软件,对梯度复合材料活塞的隔热效果进行了分析,分析结果显示隔热度提高了8.7％。     

碳纤维表面生长纳米碳管及其增强的炭/炭复合材料

采用化学气相沉积工艺在碳纤维表面生长了纳米碳管,将此种碳纤维作为增强材料,以中间相沥青为基体炭前驱体采用浸渍炭化工艺制备了炭/炭复合材料.观察了所得复合材料断口的微观形貌,测试了抗弯强度及热物理性能.结果表明,碳纤维表面的纳米碳管可以有效地提高纤维与基体的粘结力,复合材料的抗弯性能提高了50%,而对复合材料的导热性能影响较小.     

金属基复合材料实型熔铸颗粒强化技术的研究

把实型铸造与熔铸技术有机结合提出金属基复合材料颗粒强化新技术。通过在实型铸造的泡沫材料的特定部位，事先将高性能合金进行弥散分布处理，浇铸金属母液，在金属结晶凝固过程中，在保持基体材料成分及性能不变的情况下，一次性获得表层或内表层具有特殊性能的金属基复合材料铸件。复合材料层成分、组织由表层向基体呈梯度分布，厚度可控，可以进行机械后加工。     

热处理对SiC_p／ZL109复合材料机械性能和物理性能的影响

试验分析了不同热处理方法对ＳｉＣｐ／ＺＬ１０９复合材料机械性能和物理性能的影响；通过金相和透射电镜分析研究了其热处理强化机理．结果表明．Ｔ６热处理可大幅度提高复合材料的强度；Ｔ４热处理在提高强度的同时可增加复合材料的延伸率；复合材料强度的提高是由于ＳｉＣｐ的均匀分布和ＳｉＣｐ与Ａｌ基体热膨胀系数差导致的高密度位错产生的．     

Mo/PSZ系复合材料的热学、力学性能与组成的关系

在全组成范围内对Mo/PSZ系两相复合材料进行了组织结构的定量表征和热物理性能及高温力学性能的测试，详细讨论了两相复合材料在不同温度下热传导特性和变形、破坏特性和复合组织的依存关系。实验结果证明，Mo/PSZ系复合材料的热传导率、变形及破坏举动等特性不仅与测定温度和组成有关，而且强烈依存于复合材料的组织特征。     

陶瓷纤维增强铝合金的制造工艺和性能研究

用国产氧化铝和硅酸铝陶瓷纤维为增强材料制造铝基复合材料，前者性能稳定，受制造工艺变的影响小；后者的性能与制造工艺和纤维性质有关，其中，纤维制造方法，纤维打断时间，预制体用粘接剂和挤压铸造的压力对合金性能的影响明显。     

Compressive strength of carbon nanotubes grown on carbon fiber reinforced epoxy matrix multi-scale hybrid composites

The characteristics of interface between fiber reinforcement and matrix have a strong influence on the properties of a composite material. Multiwalled carbon nanotubes were grown on carbon fibers by catalytic decomposition of acetylene using thermal chemical vapor deposition technique at 700 °C to modify the fiber surface. Unidirectional multi-scale composites were fabricated using these carbon nanotubes grown fibers with epoxy matrix. As the nanotubes were directly grown on the fibers they get strongly attached with the fibers thus modifying their surface condition which in turn alters the fiber/matrix interface. Modification of the fiber/matrix interface is therefore expected to change the properties of composites. The compressive strengths of these composites were measured which showed a significant enhancement of 43% and 94% in the longitudinal and transverse compressive strengths respectively as compared to composites made of carbon fibers which underwent a similar thermal cycle but without carbon nanotubes growth. The morphology of CNTs grown on carbon fibers was examined at nano-level using HRTEM which showed growth of carbon nanotubes with different morphology and diameter ranging from 5-50 nm.     

纤维增强铝基复合材料及其应用

纤维增强铝基复合材料由于具备各种特殊性能或优良的综合性能,越来越受到人们的重视。讨论了纤维增强铝 基复合材料的主要组成部分——作为增强剂的纤维,并列举了若干典型纤维增强铝基复合材料的性能,以及纤维增强铝基 复合材料应用实例。     

钢纤维增强有色金属基复合材料综述

有色金属基复合材料相对于传统有色金属材料而言,具有更好的抗氧化性、高耐热性、高比强度、高比模量、耐磨损和高使用寿命。在有色金属基复合材料的众多的增强体中,非金属纤维(C/C、SiC)与金属基质结合界面的相容性是制约金属基复合材料性能的关键问题,而金属纤维与金属基质之间良好的相容性能够有效改善金属材料的性能。金属纤维增强有色金属基复合材料的制备工艺主要有扩散粘结法、液态渗透法、压力铸造法、涂层热压法、双辊轧制法。 本文主要总结了钢纤维增强有色金属基(Al、Mg、Cu、Zn和Zr)复合材料的制备方法、微观组织、界面特征和机械性能,指出了钢纤维增强有色金属基复合材料进一步研究发展所需要解决的问题。     

The first matrix cracking behavior of fiber-reinforced ceramic matrix composites

First matrix cracking stress in fiber reinforced ceramic composites is an important design parameter as it signifies the onset of mechanical damage and subsequent degradation of fiber and interface properties due to oxidation and corrosion. In this study, the influence of variation in the matrix crack length and fiber volume fraction on the first matrix cracking stress of ceramic matrix composites is investigated. To this end, zircon matrix composites uniaxially reinforced with silicon carbide fibers and monolithic zircon were fabricated. The monolithic and composite samples were microindented to create flaws of controlled size on the surface, and were then tested in 3-point flexure to obtain the matrix cracking stress. The results obtained from this study clearly indicated the non-steady state (short crack) and steady state (long crack) matrix cracking behaviors in ceramic matrix composites. The experimental results are compared with the theoretical results based on the fracture mechanics analyses published previously.     

Improved wettability and mechanical properties of metal coated carbon fiber-reinforced aluminum matrix composites by squeeze melt infiltration technique

In order to improve the wettability and bonding performance of the interface between carbon fiber and aluminum matrix, nickel- and copper-coated carbon fiber-reinforced aluminum matrix composites were fabricated by the squeeze melt infiltration technique. The interface wettability, microstructure and mechanical properties of the composites were compared and investigated. Compared with the uncoated fiber-reinforced aluminum matrix composite, the microstructure analysis indicated that the coatings significantly improved the wettability and effectively inhibited the interface reaction between carbon fiber and aluminum matrix during the process. Under the same processing condition, aluminum melt was easy to infiltrate into the copper-coated fiber bundles. Furthermore, the inhibited interface reaction was more conducive to maintain the original strength of fiber and improve the fiber–matrix interface bonding performance. The mechanical properties were evaluated by uniaxial tensile test. The yield strength, ultimate tensile strength and elastic modulus of the copper-coated carbon fiber-reinforced aluminum matrix composite were about 124 MPa, 140 MPa and 82 GPa, respectively. In the case of nickel-coated carbon fiber-reinforced aluminum matrix composite, the yield strength, ultimate tensile strength and elastic modulus were about 60 MPa, 70 MPa and 79 GPa, respectively. The excellent mechanical properties for copper-coated fiber-reinforced composites are attributed to better compactness of the matrix and better fiber–matrix interface bonding, which favor the load transfer ability from aluminam matrix to carbon fiber under the loading state, giving full play to the bearing role of carbon fiber.     

Effect of alumina short fiber and air-cooling processing on solidification microstructure and tensile properties of Al2O3/Al-15Si composites

The effect of microstructure variation by addition of alumina short fiber and optimization of tensile properties by air-cooling processing in Al2O3/Al-15Si composites were studied.The results show that in Al-015Si alloy matrix composites with 14% and 30%(volume fraction)fiber,the primary silicon is hardly refined,but the eutectic silicon is effectively refined and granulated.Granulation of some eutectic silicon mainly happens in fiber segregation areas.Refining and granulation of the eutectic silicon are related to the physical constraint arising from the fiber,After the 30%Al2O3/Al-15Si composite was remelted and air-cooled,the number of the eutectic silicon on the surface of the fiber increases,which results in the improvement of fiber/matrix interface and tensile properties for the as-cast composite,Air-cooling processing may be reliable for the optmization of the microstructure and properties of fiber reinforced hypereutectic Al-15Si alloy composites.     

Electromechanical response of 1–3 piezoelectric composites: A numerical model to assess the effects of fiber distribution

A finite element-based numerical model is developed to characterize the effects of fiber distribution in 1–3 piezoelectric active fiber/active matrix composites under primarily static electric fields and elastic stress conditions. Upon identifying 14 characteristic periodic and randomized fiber configurations, the influence of fiber distribution on the coupled response of model ceramic–matrix and polymer–matrix fiber composites with widely different constituent material properties is examined. It is demonstrated that: (i) while certain fiber arrangements provide a higher packing density than others, the fundamental elastic, dielectric and piezoelectric material constants of the 1–3 piezoelectric composites remain largely insensitive to the nature of (periodic or randomized) fiber distributions in the matrix; (ii) the piezoelectric figures of merit of the composite are also invariant to differences in fiber distribution; and (iii) the distribution of internal stresses in the piezoelectric composites in response to mechanical loads tend to be modulated by the nature of the fiber configuration, with the square edge and randomized fiber distributions providing reduced levels of interfacial stresses.     

碳纤维含量对Al2O3+C/ZL109混杂复合材料摩擦磨损性能的影响

利用挤压铸造法制备了A1203 C／ZLl09短纤维混杂金属基复合材料，并探讨了A1203纤维体积分数为12％时，C纤维含量对该混杂复合材料摩擦磨损性能的影响。结果表明：随着C纤维体积分数的增加，复合材料的摩擦因数和磨损率逐渐降低。12％A1203和4％C短纤维的协同作用使复合材料从轻微磨损到急剧磨损的临界转变载荷比基体合金提高了1倍。当载荷低于临界载荷时，复合材料的主要磨损机制为犁沟磨损和层离，C纤维的加入有利于磨损表面裂纹尺寸的减小。但随着载荷的逐渐增加并发生严重磨损时，基体和复合材料的磨损机制均为严重的粘着磨损甚至局部熔化磨损。     

Effect of applied pressure on mechanical properties of squeeze cast mg matrix composites

The present study aims at investigating the correlation of microstructure and fracture properties of two AZ91 Mg matrix composites fabricated by squeeze casting technique with a variation of the applied pressure. The composites were reinforced with Kaowool alumino-silicate short fibers and Saffil alumina short fibers, respectively. Microstructural observation, fractographic observation, andin situ fracture tests were conducted on these composites to identify the microfracture process. From thein situ fracture observation of the Kaowool reinforced composites, microcracks were initiated at the short fiber/matrix interfaces for the composite processed with the lower applied pressure, whereas microcracks were initiated easily at short fibers already cracked during squeeze casting at the very low stress intensity level for the composite processed with the higher applied pressure. Thus in this case. the effect of the applied pressure on mechanical properties could be explained using a competing mechanism; the detrimental effect of fiber breakage might override the beneficial effect of the grain refinement and the densification as the applied pressure was increased. On the other hand, for the composites reinforced with Saffil short fibers, microcracks were initiated mainly at the fiber/matrix interfaces at the considerably high stress intensity factor level while the degradation of fibers was hardly observed even in the case of the highest applied pressure. This finding indicated that the higher applied pressure yielded the better mechanical properties on the basis of the reinforcing effect of Saffil short fibers having excellent resistance to cracking.