SiCw／LD2A1复合材料超塑变形协调机制的研究

为了研究金属基复合材料超塑变形时液相的作用,分析了金属基复合材料界面处的局部应力,当由滑移引起的界面处局部分应力值高于界施加于同处应力值时,复合材料在含有液相的状态下超塑变形能力量大,反之,变形能力在不含液相的纯固相状态最大,因此,可以认为塑性变形过程中当有应力集中产生时,为了缓解应力集中,液相必需存在才能取得超塑性,当无应力集中时,超塑变形不需要液相的存在,上述理论与实验结果是一致的。     

SiCw/LD2Al复合材料超塑变形协调机制的研究

为了研究金属基复合材料超塑变形时液相的作用,分析了金属基复合材料界面处的局部应力.当由滑移引起的界面处局部应力值高于外界施加于界面处应力值时,复合材料在含有液相的状态下超塑变形能力最大;反之,变形能力在不含液相的纯固相状态最大.因此,可以认为塑性变形过程中当有应力集中产生时,为了缓解应力集中,液相必需存在才能取得超塑性.当无应力集中时,超塑变形不需要液相的存在.上述理论与实验结果是一致的.     

铝基复合材料高应变速率及低温超塑性的研究进展

综述了低温与高应变速率铝基复合材料超塑性的变形机理、制备工艺以及工业应用的研究现状和最新研究成果,并在目前已有研究的基础上展望了超塑性铝基复合材料的广阔应用前景。     

3Y—TZP陶瓷超塑性应变速率敏感性指数及晶界玻璃相

研究了应变量，温度及测试技术对３Ｙ－ＴＺＰ陶瓷超塑性应变速率敏感性指数ｍ的影响。     

原位生成(TiBw+TiCp)/Ti复合材料的高应变速率超塑性

将纯钛粉和B4C粉按一定比例混合均匀后,通过反应热压方法原位合成制备了TiB晶须和TiC颗粒增强体积分数为3%的钛基复合材料,并在950℃以16∶1的挤压比对复合材料进行了高温热挤压变形.采用X射线衍射仪和扫描电镜分别研究了原位生成复合材料的相结构和微观组织,并在700℃以不同应变速率对钛基复合材料进行了高温拉伸变形.研究表明:纯钛和B4C在1200℃真空热压原位合成产生两种不同形状的增强体,即短纤维状TiB晶须和等轴状的TiC颗粒;应变速率为5.95×10-4、1.19×10-3s-1和0.89×10-2s-1时,(TiBw TiCp)/Ti复合材料都表现出超塑性,延伸率分别为205.43%、148.3%和112.85%;700℃变形时(TiBw TiCp)/Ti复合材料的应变速率敏感指数为0.45.     

金属基复合材料微区力学性能的不均匀现象

利用超显微硬度仪测量纤维，颗粒增强铝基复合材料内不同微区的超显微硬度，发现界面区附近超显微硬度值明显增高，显微硬度值与基体，增强体的性质，界面性能，增强体的尺寸，形状，分布有密切关系。微区力学性能的不均匀性将影响复合材料的宏观性能和尺寸稳定性。     

外部因素对金属基复合材料磨损性能的影响

综述和分析了正载荷、滑动速度、滑动距离、环境温度等外部因素对金属基复合材料磨损性能的影响。与复合材料内部影响因素类似,外部因素通过影响复合材料磨损机制而影响复合材料磨损率。     

铸锭铝合金Al-Cu-Mg-Ti高应变速率超塑性

采用常规熔铸、热处理、小挤压比挤压及轧制这一低成本并适合于工业化规模应用的路线,研制了一种具有高应变速率超塑性的铸锭铝合金Al-Cu-Mg-Ti.拉伸试验结果表明在温度为793K、初始应变速率为3.16×10-1s-1的拉伸变形条件下,其超塑伸长率为218%,流变应力为32.5MPa.断面及表面形貌SEM分析和初熔行为的DSC分析表明,该合金高应变速率超塑性变形来自于晶界滑动和位错滑移,与液相没有关系.     

高阻尼金属基复合材料的发展途径

在综述传统高阻尼金属材料和金属基复合材料的阻尼特性的基础上，探讨获得高阻尼性能的金属基复合材料的途径，指出采用高阻尼的基体合金，采用高阻尼的增强物以及设计高阻尼的界面层是效的三种方法，为发展密度更小同时又集结构与阻尼功能于一体的新型材料提供了可能。     

电子封装用金属基复合材料的制备

分析了电子封装用金属基复合材料的性能特点及其对制备工艺的要求，在此基础上论述了该种材料的各种制备工艺的特点及发展现状。     

High-strain-rate superplasticity of SiC p /8090 aluminum composite

Superplastic tensile tests of a 17 vol.% SiC _p /8090 Al-Li composite were carried out at strain rates ranging from 7.25 × 10^-4 s^-1 to 3.46 × 10^-1 s^-1 and at temperatures from 773 K to 873 K. A maximum elongation of 300% was obtained at a strain rate of 1.83 × 10^-1 s^-1 when tested at a temperature of 848 K which was slightly above the solidus temperature of the composite. The effect of a small fraction of liquid phase on high-strain-rate superplasticity was discussed. Finally, the activation energy of high-strain-rate superplastic deformation was calculated and high-strain-rate superplastic mechanism was discussed.     

非连续增强金属基复合材料剧烈塑性变形行为研究进展

综述了非连续增强金属基复合材料剧烈塑性变形(SPD)行为的研究进展,系统阐述了等径弯曲通道变形(ECAP)、高压扭转(HPT)、多向锻造(MF)、累积叠轧(ARB)和循环挤压压缩(CEC)5种SPD的加工原理和方法。集中介绍了这些方法在铝基、镁基、铜基和钛基等金属基复合材料方面应用的研究进展。重点介绍了金属基复合材料SPD的微观组织演化和变形力学行为,详细阐明了金属基复合材料SPD机制以及超细晶形成机理,指出了金属基复合材料在SPD中存在的深层次问题及发展趋势,展望了利用SPD方法制备超细晶非连续增强金属基复合材料的应用前景。     

Hot isostatic processing of metal matrix composites

The effect of four different Hot Isostatic Pressing (HIPping) treatments on porosity in the aluminium casting alloy A357 and stir-cast A357/15 vol% SiC particulate MMC has been investigated and the optimum treatment identified. The bend strength increased after HIPping relative to as-received. Such ceramic particle reinforced MMCs, however, do not have adequate toughness for many commercial applications. Metal reinforced MMCs made by combining an Al alloy matrix with stainless steel wire can provide a compromise between weight saving and toughness. The production, involving HIPping, of such a composite is discussed.     

金属基复合材料的发展及应用

本文主要论述了金属基复合材料 (MMCs)的类型、制备、发展、应用及其回收再生 ,目前 ,在MMCs发展和应用中 ,SiC和Al2 O3颗粒增强铝基复合材料仍占主要地位。本文着重介绍了颗粒增强铝基复合材料的性能及其成型加工特性。     

High-speed turning experiments on metal matrix composites

The hard abrasive ceramic component which increases the mechanical characteristics of metal matrix composites (MMC) causes quick wear and premature tool failure in the machining operations. The aim of the paper is to compare the behaviour of high rake angle carbide tools with their diamond coated versions in high-speed machining of an Al₂O₃Al 6061 MMC. The influence of the cutting parameters, in particular cutting feed and speed, on tool wear and surface finish has been investigated. The higher abrasion resistance of the coatings results in increased tool life performances and different chip formation mechanisms.     

石墨烯增强金属基航空复合材料研究进展

本文综述了石墨烯增强金属基航空复合材料的研究现状,归纳了该种复合材料的制备方法,讨论了石墨烯对其性能的影响及机制。指出目前高含量、排列石墨烯增强金属基航空复合材料的研究还比较缺乏,涉及的工艺参数、组织结构、界面化学及高温物理性能等相关问题仍需进一步研究,并提出未来的研究重点应由制备方法等工艺性探讨向微观复合构型设计的思路转变。     

Behaviour of coatings on reinforcements in some metal matrix composites

Coating on reinforcements affects the interface bonding of a composite, and is therefore usually used for improving the composite's properties. The behaviour of SiC coating on carbon fibre in reinforced aluminium metal castings, Fe on carbon fibre-reinforced copper and alumina coating on K₂O · 6TiO₂ whisker-reinforced aluminium composites were investigated, respectively, by modern techniques such as TEM, SEM etc. with the goal of controlling the interfacial interaction and wettability of reinforcement with the matrices. SiC coating produced by a polycarbosilane solution process effectively improved the strength because it successfully controlled oxidation of the carbon fibres themselves and the harmful reaction between the carbon fibres and molten aluminium during the fabrication process and heating process of the composites. The metal coating, Fe, made by electrical plating, strengthened the bonding of carbon fibres with copper by changing the bonding state of the interface from a mechanical one to a partly chemical one. Therefore the strengths of the resulting composites were improved. The alumina coating on K₂O · 6TiO₂ also controlled the diffusion of the K element from the whiskers into the aluminium matrix and altered the reaction with aluminium, and led to the optimization of interfacial bonding between the whiskers and a superior composite.     

Non destructive ultrasonic evaluation of fibrous metal matrix composites

An iterative numerical elastic constants optimization method associated to a classical ultrasonic immersion device is used for the entire characterization of two kinds of metal matrix composites. The usual methods of optimization are generally based on Newton's algorithm. Sometimes this algorithm converges towards relative minima that gives elastic constants which do not correspond to the physical reality of the material. As a remedy, we have developed a numerical analysis technique based on a different algorithm allowing a better convergence to the unique global solution. Using the Levenberg-Marquard algorithm, the methodology to recover the elastic constant, consists in minimizing the square deviation between calculated velocities and the experimental ones measured under variable incidence from a computer controlled ultrasonic immersion device.     

Innovative light metals: metal matrix composites and foamed aluminium

Low weight is required especially for those means of transport, in which material properties have to be evaluated with respect to their specific mass. The possibility of increasing the specific properties of recyclable light metals are described: reinforcements by ceramic particulates, by continuous ceramic or carbon fibres, or by the reduction of weight by foaming the metal. Examples of castings, extrusions and forgings of particulate reinforced (<30 vol.%) aluminium alloys are given and their advantages including stiffness and wear resistance are presented. The technique of selective reinforcements by co-extrusion of particulate reinforced alloys together with conventional alloys is described. High volume fractions (>40 vol.%) of reinforcements can be produced by gas pressure infiltration of either particulate or fibre preforms. In the case of aluminium matrix, the specific strength can be increased by a factor of up to 15, and the specific stiffness by a factor of up to 7, whereas for carbon fibre reinforced magnesium the specific strength can be increased even more. The anisotropy of fibre reinforced metal matrix composites is discussed as well as the possibilities to use cross ply preforms. The technique of foaming aluminium alloys yields materials with a specific mass in the range of 0.3–1.0 g/cm³. Such structures with essentially closed pores exhibit higher specific stiffness for beams and membranes than massive metal. The measurement and definition of stiffness and strength values appropriate for aluminium foams are presented by referring to compression tests.     

金属基复合材料发展的挑战与机遇

装备技术的升级换代和转型为材料研发带来了前所未有的挑战,金属基复合材料(MMCs)具有极好的可设计性,可迎接这种挑战。有效地利用不同性质、形态、尺度的无机非金属及碳等材料作为MMCS增强体,可为其获得丰富的性能与功能,这是MMCs的未来发展趋势和机遇。简要介绍了笔者在MMCs设计研究中的几项尝试经验和实例,包括自润滑功能性界面设计、非烧蚀功能性设计、材料高温恒刚度性能设计、地磁屏蔽结构-功能一体化设计和高强韧固溶体界面设计,证明了MMCs性能与功能设计的有效性。