高体积分数B4C/ZL101复合材料力学性能的研究

高体积分数颗粒增强金属基复合材料结合了陶瓷和金属的性能优势,具有轻质、高强、高模量的特点,是一种颇具应用前景的装甲材料,但此方面的报道研究较少。采用压力浸渗法制备了颗粒体积分数为50%、不同粒径的B4C/ZL101复合材料。结果表明,预制件温度为550℃、浸渗熔体温度为750℃时,采用压力浸渗可以得到颗粒分布均匀、致密度高的复合材料,组成相简单;复合材料的力学性能表明,B4C颗粒的粒径越小,复合材料的力学性能越好。当B4C颗粒粒径为3μm时,压缩强度、抗弯强度、布氏硬度分别可达1000MPa、640MPa、285HB。     

浸渗法制备双连续TiB2/(Cu,Ni)复合材料的组织和性能

用高温粉末烧结结合自发浸渗法制备高TiB2含量(体积含量约为86%)的双连续TiB2/(Cu,Ni)复合材料,研究了不同陶瓷体积含量多孔材料对TiB2/(Cu,Ni)复合材料微观组织和力学性能的影响.采用XRD和SEM分析了复合材料的相组成和微观结构,用三点弯曲试验测试了复合材料的弯曲强度和断裂韧性.结果表明:经过预制坯高温烧结后自发熔渗金属是制备致密的双连续TiB2/(Cu,Ni)复合材料的有效方法,复合材料的致密度和力学性能得到显著提高;当TiB2陶瓷体积含量为81.6%以及浸渗温度为1500℃条件下,TiB2/(Cu,Ni)复合材料的弯曲强度和断裂韧性分别达到640.5 MPa和9.37 MPa·m1/2,相对密度为98.4%.     

Cf/Mg 复合材料异形件成形装置设计与实验研究

为实现Cf/Mg复合材料异形件的近净成形,在分析金属基复合材料液态浸渗制备技术的基础上,提出了真空压力浸渗-液固挤压制备Cf/Mg复合材料新工艺,并设计了相应的成形装置.利用设计的装置开展2D碳毡增强镁基复合材料异形件的制备研究.在熔炼温度为760~820℃,预制体预热温度为570~610℃,浸渗气压0.5 MPa和挤压载荷10~30 MPa等工艺参数下,成功制备出Cf/Mg复合材料异形制件.对复合材料制件进行宏观尺寸测量及扫描电镜(SEM)观察发现,制件外形完整,与设计一致;制件内部组织致密、纤维分布均匀;预制体在制备过程中没有发生明显的变形和破坏.     

颗粒分散技术在真空液相浸渗制备Cf/Al复合材料中的应用

采用真空反压液相浸渗工艺,以碳纤维增强铝为研究对象,探讨了M40J纤维增强AlMg10复合材料制备工艺中,SiC及淀粉分散颗粒对复合材料微观组织及性能的影响。结果表明,碳化硅可以减少铝液在束内的浸渗阻力,并使纤维分布均匀,从而提高复合材料构件的成型性和力学性能。经过5%SiC+3%淀粉溶液的分散后,复合材料的体积分数由72%降低到51%,而复合材料的拉伸强度提高了131MPa,达到498MPa。     

成型压力对5428VB/T700复合材料微观结构与性能的影响

5428VB/TT00预浸料适于真空成型高性能复合材料.为了进一步提高该类材料的通用性,本工作采用热压罐法成型5428VB/TT00复合材料,研究了加压时机、施加压力大小等对复合材料基本力学性能的影响,采用超声扫描、微观结构分析等对复合材料板材质量进行了分析,并和相应的真空成型5428VB/T700复合材料进行了比较.结果表明,在130℃/1h前施加0.3～0.6MPa的压力,5428VB/T700复合材料的短梁剪切强度相对于真空压力成型体系有较明显降低,但随压力的增大有增加趋势;在130℃/1.5～2.0h施加0.3～0.6MPa压力时,5428VB/T700复合材料的基本力学性能相对于130℃/1h前施加压力的体系有较明显提高,并随压力的增大有增加趋势,当施加的压力达到0.6MPa以上时,复合材料的基本力学性能和质量优于相应的真空压力成型复合材料体系.分析了复合材料成型过程中的气泡运动历程以及孔隙的形成原因等.     

气压浸渗法制备ZrC-W-Cu复合材料的显微组织与力学性能

为提高钨渗铜材料的性能以适应先进推进技术发展的需求,以ZrC粉和W粉为原料,采用无压烧结工艺制备ZrC-W多孔骨架,进而采用气压浸渗工艺对开气孔在20％左右的ZrC-W骨架压力渗铜,制备出ZrC-W-Cu复合材料.研究ZrC含量对ZrC-W骨架开气孔率、压缩强度及ZrC-W-Cu复合材料的显微组织和力学性能的影响规律.结果表明:随着ZrC含量(体积分数,下同)的增加,ZrC-W骨架的开气孔率先升高后降低,在ZrC含量为10％时开气孔率最大,为29.77％;ZrC-W骨架的压缩强度随ZrC含量的增加而下降,且整体低于W骨架;ZrC-W-Cu复合材料维氏硬度随ZrC含量的增加逐步增大,在ZrC含量为15％时达到3.26 GPa;弹性模量基本不变;断裂韧度随着ZrC含量的增加先升高后降低,抗弯强度在ZrC含量为4％时达到最大值,为1243 MPa.     

FLiNaK熔盐浸渗对2D C/C复合材料力学性能的影响

在650℃不同压力下将熔融的LiF-NaF-KF盐(46.5%-11.5%-42.0%,摩尔分数,FLiNaK)浸渗入2D C/C复合材料中,测试2D C/C复合材料的增重率、密度和力学性能的变化并用X射线断层扫描(X-ray CT)和扫描电子显微镜(SEM)观察FLiNaK熔盐的分布,研究了FLiNaK熔盐浸渗对2D C/C复合材料力学性能的影响。结果表明,FLiNaK熔盐分布在2D C/C复合材料开放的孔隙中、纤维束中和相邻层的裂缝中;随着浸渗压力的提高2D C/C复合材料的增重率增大、压缩强度和弯曲强度提高。FLiNaK熔盐浸渗产生的“二次增密”作用和2D C/C复合材料中残余应力的耦合效应,使其力学性能提高。     

碳含量对反应烧结SiC/B4C力学性能的影响（英文）

采用渗硅反应烧结工艺制备了SiC/B4C复合材料,并研究了碳含量对复合材料的力学性能及微观结构的影响。结果表明,SiC/B4C复合材料的力学性能(硬度、抗弯强度、韧性)随着碳含量的增加呈先增强后减弱的趋势。在碳含量为10vol%的条件下,复合材料的综合性能最佳,其硬度、抗弯强度和韧性分别为19.63 Gpa、358 MPa和3.96 MPa?m1/2。此外,当碳含量不足10vol%,复合材料的组织随碳含量增加均匀性提高;当碳含量超过10vol%,显微组织均匀性变差,并且添加碳粉后,复合材料由沿晶、穿晶混合断裂向穿晶断裂转变,最终导致SiC/B4C复合材料力学性能的改变。     

催化炭化-原位反应/反应熔体浸渗法制备C/C-SiC复合材料

利用三氯化铝为催化剂、煤焦油为前驱体催化炭化致密化碳毡制备C/C复合材料,在此基础上结合同步浸渍原位反应或反应熔体浸渗过程制备C/C-SiC复合材料,并对复合材料的微观结构、力学性能等进行表征分析.结果表明:在催化炭化-原位反应法制得的C/C-SiC复合材料中,SiC多以纳米线的形式存在于碳纤维束内部和碳纤维束之间的孔隙,C/C-SiC复合材料总体表现出假塑性断裂模式,其弯曲强度达到了(158±12)MPa;而催化炭化-反应熔体浸渗法制得的C/C-SiC复合材料中,SiC以立方体、六方体颗粒存在,复合材料的断裂行为呈现出脆性断裂模式,弯曲强度达到了(150±10)MPa.相对于催化炭化-反应熔体浸渗法,催化炭化-原位反应法所得到的C/C-SiC复合材料具有工艺简单、成本低、力学性能优异等诸多优势.     

C/C泡沫预制体液相硅浸渗制备C/SiC复合材料研究

以中间相沥青浸渍整体碳毡发泡技术制备的一种新型多孔C/C泡沫复合材料为预制体,通过液相硅浸渗(LSI)工艺制备了C/SiC复合材料,研究了预制体不同孔隙率对Si浸渗及C/SiC复合材料力学性能和微观形貌的影响,分析了复合材料的物相组成和晶体结构.结果表明,采用发泡技术可以快速有效地实现C/C预制体的致密化处理.预制体孔隙率为65.41%时液相硅浸渗处理后所得复合材料性能最好,密度为2.64g/cm3,弯曲强度为137MPa,弹性模量为150GPa.纤维未作表面抗硅化涂层处理以及复合材料中存在闭孔是C/SiC复合材料性能不佳的主要原因.     

A study of silica coatings on the surface of carbon or graphite fiber and the interface in a carbon/magnesium composite

A study has been made of the method of depositing a silicon dioxide coating on the surface of carbon or graphite fibers and of the interface in C/Mg composites manufactured by vacuum pressure infiltration: the mechanical properties of the materials were also studied. For the coating process, the fibers were passed through a toluene solution containing a silicon-based organometallic compound and chloride, following which hydrolysis and pyrolysis of the organometallic compound occurred to form a thin and uniform silicon dioxide coating on the surface of the fibers. The air-stable silicon dioxide coating facilitates wetting and bonding between carbon or graphite fibers and liquid magnesium. The carbon- and graphite-fiber-reinforced magnesium composites were fabricated by vacuum/pressure infiltration processing. Special attention was focused on analysis of the structure of the coating which was deposited by the solution immersion process with the aid of analytic instruments such as SEM, EDAX, TEM, XPS and SAM. Manufacturing processes of C/Mg composites, the interface chemical reaction, and the mechanical properties were also studied.     

Chemical vapor deposition of titanium nitride on carbon fibres as a protective layer in metal matrix composites

The significance of carbon fibres for reinforcing metals has increased in the last years, because of their excellent mechanical properties. However, to avoid the weakening reaction during MMC fabrication between the fibre and the liquid metal, a protective coating has to be applied. Continuous carbon fibre roving with 6000 filaments were coated with TiN by thermal induced chemical vapour deposition (CVD) using a gas mixture of TiCl₄, N₂ and H₂ as a precursor. The deposition process in the reactor was simulated by a modified Phoenics-CVD software program using a 2D-axisymmetric model. Carbon fibres reinforced magnesium matrix composites are fabricated by a pressure infiltration casting process. The mechanical properties of the MMCs can be used to demonstrate the efficacy of the coated fibre approach. The rule of mixture is realized to 98% for the coated fibre, and only 48% for the uncoated system. The infiltration pressure during the processing of composites was lowered from 10 to 1 MPa for the TiN coated system.     

粉末冶金法炭纤维/Mg复合材料的界面对其力学性能的影响

采用表面化学镀镍前后的短炭纤维(Cf)做为增强体,纯镁粉为基体金属,通过粉末冶金法和热挤压制备镁基复合材料.采用SEM-EDS、TEM、XRD和拉伸等测试手段表征短炭纤维增强镁基复合材料的微观形貌、元素组成、物相组成及其力学性能.结果表明:炭纤维在复合材料中分布均匀且沿挤压方向定向排列;采用经过表面化学镀镍处理的短炭纤维与金属镁复合后界面结合状态优良,Mg2Ni物相的存在表明润湿性的改善是通过金属镁与涂层发生反应而实现;对比屈服强度测试值和理论计算值的大小,表明涂层炭纤维增强镁基复合材料的增强机理主要是界面载荷传递效应.     

SiC<Subscript>f</Subscript>/SiC composites reinforced by randomly oriented chopped fibers prepared by semi-solid mechanical stirring method and hot pressing

SiC short fibers, with an average diameter of 13 μm, length of 300–1,000 μm and chopped from SiC continuous fibers, were surface modified by the semi-solid mechanical stirring method to produce a discrete coating of aluminum particles. Then the starting mixtures, which consist of SiC short composite fibers, aluminum powder less than 50 μm and α-SiC powder of an average diameter of 0.6 μm, were mechanically mixed in ethanol for about 3 h, dried at 80 °C in air, and hot pressed under 30 MPa pressure at 1,650, 1,750 and 1,850 °C with 1 h holding time to prepare SiC_f/SiC composites. Volume fraction of SiC short fibers in the starting powder for SiC_f/SiC composites was about 25 vol.%. The composites were characterized in terms of bulk density, phase composition, and mechanical properties at room temperature. In addition, the distribution of SiC short fibers in the matrix and the cracking pattern in the composites were examined by optical microscope. Fracture surface of the composites were performed by a scanning electron microscope (SEM). The effect of hot-pressing temperature on bulk density and mechanical properties was investigated. The results indicated that SiC short fibers were uniformly and randomly distributed in the matrix, bending strength and bulk density of the composites increased with increasing sintering temperature. The composite, hot-pressed at 1,850 °C, exhibited the maximum bulk density and bending strength at room temperature, about 3.01 g/cm³ and 366 MPa, respectively. SEM analyses showed that there were a few of fiber pullout on the fracture surface of samples sintered at 1,650 °C and 1,750 °C, which was mainly attributed to lower densities. But few of fiber pullout was observed on the fracture surface of sample sintered at 1,850 °C, the combined effects of high temperature and a long sintering time were considered as a source of too severe fiber degradation because of the large amount of oxygen in the fibers.     

Influence of fibre-matrix interactions and of matrix microstructure on the mechanical properties of Aluminium-based MMCs reinforced with Altex fibers and processed by medium pressure infiltration

The introduction of alloying elements in an aluminium matrix may have a detrimental effect on the mechanical properties of unidirectional composites. The aim of this work was to establish a correlation between the mechanical properties of Aluminium based/Altex fibers MMCs processed by medium pressure infiltration and their microstructure, the composition of the matrix and the mechanical properties of the fibers. Al-Mg, Al-Si, Al-Mg-Si and Al-Mg-Si-Cu matrices were studied. The microstructure of the composites was characterized by optical and electron microscopy observations. Transmission electron microscopy was also used to investigate the reactivity phenomena likely to occur between the matrix and the fibers. Furthermore, the tensile properties of the fibers after introduction in the metal matrix were measured by single fiber tests, to assess the degradation of the fibers. The tensile properties of the composites were also determined both in longitudinal and transverse direction. They were interpreted referring to the microstructural state of the composites and to the tensile properties of the fibers. Lastly, the detrimental effects due to the alloying elements (solid or liquid state reactivity, presence of brittle phases, matrix hardening) were classified according to their importance.     

Effect of holding pressure on densification and mechanical properties of Cf/Mg composites

Carbon fibre reinforced magnesium alloy matrix composites were fabricated by using liquid–solid extrusion directly following vacuum infiltration technique. The experimental results showed that the microstructures of C_f/Mg composites depended on the holding pressure. The porosity was reduced gradually, and the densification was improved obviously, respectively, with the increase of the holding pressure. The densification, hardness and Ultimate tensile strength of C_f/Mg composites were significantly improved as the holding pressure increased in the range of 0.1–15 MPa. The densification was not obvious, but the UTS of the C_f/Mg composites decreased gradually as the holding pressure increased in the range of 25–45 MPa. The C_f/Mg composites presented a good performance when the holding pressure was about 15 MPa.     

SiCp/Al Composites Fabricated by Modified Squeeze Casting Technique

A cost effective method was introduced to fabricate pure aluminum matrix composites reinforced with 20% volume fraction of 3.5 μm SiC particles by squeeze casting followed by hot extrusion. In order to lower volume fraction of the composites, a mixed preform containing pure aluminum powder and the SiC particles was used. The suitable processing parameters for the infiltration of pure aluminum melt into the mixed preform are： melt temperature 800℃, preform temperature 500℃, infiltration pressure 5 MPa, and solidification pressure 50 MPa. Microstructure and properties of the composites in both as-cast and hot extruded states were investigated. The results indicate that hot extrusion can obviously improve the mechanical properties of the composite.     

Csf/BAS玻璃陶瓷复合材料的制备及其力学性能研究

为了提高钡长石(BAS)玻璃陶瓷的力学性能,采用轧膜成型、热压烧结方法制备出纤维分布均匀的致密短碳纤维增强BAS玻璃陶瓷基复合材料(Csf/BAS).采用X射线衍射分析,扫描电子显微镜、透射电子显微镜观察及三点弯曲法与单边开口梁法研究了纤维含量对复合材料组织及力学性能的影响.研究表明:Csf对BAS玻璃陶瓷有良好的强韧化效应.体积分数为30%Csf/BAS复合材料的室温抗弯强度及断裂韧性分别为255 MPa和3.45 MPa.m1/2,其主要的韧化机制为裂纹偏转、纤维的拔出与桥接.用摩尔分数25%Sr代替Ba实现了基体的六方→单斜相的完全转变,进一步提高了复合材料的力学性能.     

先驱体浸渍-裂解法制备SiBN纤维增强SiBN陶瓷基复合材料

连续纤维增强氮化物陶瓷基复合材料是耐高温透波材料的主要发展方向,纤维是目前制约耐高温透波复合材料发展的关键,而SiBN陶瓷纤维是一种兼具耐高温、透波、承载的新型陶瓷纤维。以聚硅氮烷为陶瓷先驱体,以SiBN连续陶瓷纤维为增强体,采用先驱体浸渍-裂解法制备了SiBN陶瓷纤维增强SiBN陶瓷基复合材料,研究了复合材料的热膨胀特性、力学性能、断裂模式以及微观结构。结果表明:SiBN陶瓷纤维增强SiBN陶瓷基复合材料呈现明显的脆性断裂特征,复合材料的弯曲强度和拉伸强度分别为88.52 MPa和6.6 MPa,纤维的力学性能仍有待于提高。     

硅酸铝短纤维增强镁基复合材料的界面反应及其热力学分析

用晶化的硅酸铝短纤维作增强体, 用磷酸铝作黏结剂制得预制体, 用AZ91D作基体金属, 通过挤压浸渗工艺制备镁基复合材料。通过光学显微分析、 XRD衍射分析、 SEM扫描分析等, 初步观察研究了硅酸铝短纤维增强镁基复合材料的界面反应规律和反应产物。结果表明: 用硅酸铝短纤维增强AZ91D镁合金通过浸渗挤压法制备镁基复合材料是可行的; 镁与磷酸铝黏结剂反应后在界面上生成一定数量的MgO颗粒和少量的MgAl₂O₄颗粒, 致使硅酸铝增强纤维和镁合金基体之间形成较强界面结合; 另外, 在硅酸铝短纤维的晶化处理过程中, 由于非晶态SiO₂的析出, 导致Mg₂Si脆性相在界面附近产生, 从而对该复合材料的力学性能产生一定影响。