Influence of Thermal Exposure on Mechanical Properties of C/Al Composite

In this paper were studied the microstructure and properties of the non-barrier coating compo- sites fabricated by a new technology.The bonding between C and A1 in the composites is quite well, and the composites have excellent properties.The ion probe and X-ray analyses indicate that there is Al_4C_3 phase in the composites and its amount in the composites increases when the composites are exposed.In the case of exposure the strength of the composites is reduced because of increasing amount of Al_4C_3.

PREPARATION OF Ti-Al BASED NANOPHASE COMPOSITE POWDER BY MECHANICAL ALLOYING

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Effect of CuO addition on microstructure and properties of aluminum composites produced by quick spontaneous infiltration process

Al matrix composites with a high volume fraction of reinforcements were fabricated with a compact of Al-Ti-B4C powder mixtures by quick spontaneous infiltration(QSI) process in an aluminum melt. Given the exothermal nature of the reaction between CuO and Al, a certain amount of CuO addition to the Al-Ti-B4C system dramatically increases the adiabatic temperature and thereby enables the complete combustion reaction in an aluminum melt(about 1,173 K). After the QSI process, the compact fabricated with CuO retains its original shape and the obtained composite exhibits sound microstructure containing reaction products of TiB2, Al3BC and B4C. The formation of such reinforcements when adding CuO contributes to enhancing the properties of the composites that show far superior hardness and elastic modulus of 3.03 GPa and 158.9 GPa, respectively, with lower coefficient of thermal expansion(9.44 ppm?K-1) compared to those with no CuO addition.

Thermodynamic Analysis of Combusion Synthesis and Reaction Hot Pressing of Al_2O_3/B_4C Composite

The equilibrium phases and adiabatic temperature for combustion synthesis and reaction hot pressing of Al 2O 3/B 4C employing ① Al, B 2O 3 and C ② C, B, Al 2O 3 as starting reactants were analyzed by the CALPHAD technique. It is shown that the equilibrium phases at the adiabatic temperature in the combusion system (1) are not the intended composite Al 2O 3/B 4C but other phases. Good agreement with the experimental data was achieved for the calculated adiabatic temperature. The results were discussed with respect to the elimination of the by product in the combustion synthesis. It also revealed that the reactant mixture (2) is a weak exothermic or endothermic reaction system, which can be employed in the reaction hot pressing.

Effect of TiO_2 on Synthesis of Al_4SiC_4/Al_4O_4C Composite

Al4SiC4/Al4O4C composites were synthesized based on m （ sintered clay） ： m （ active carbon ） ： m （ aluminum powder） =39： 27. 6： 33. 4, adding TiO2 powder （ anatase type, 0. 3%, 6%, 9%, respectively）, adding 〈 10% phenolic resin as binder, mixing well, pressing, drying, firing in a corundum tubular furnace in flowing argon at 1 300, 1 400, 1 500, 1 600 and 1 700℃ for 2 h, respectively. Effect of TiO2 addition on phase composition and microstructure of Al4SiC4/Al4O4C composites was investigated by TGA, chemical analysis, XRD and SEM. The results show that ： （ 1 ） Ti in the specimens loses a little in the process of firing, all residual TiO2 transforms into TiC when the firing temperature is below 1 300℃, and the formed TiC exists stably at 1 300 - 1 700 ℃; （2） the TiO2 addition has little effect on phase composition of composites ; however, when more than 3% of TiO2 is added, the formation temperature of Al4SiC4 and Al4O4C increases from 1 500 ℃ to 1 600℃ ; （ 3 ） with the concentration of Ti^4＋ increasing, Ti^4＋ may react easily with Al4SiC4 and Al4O4C forrning the finite substitution solid solution resulting in lattice defect, which leads to the decomposition of Al4SiC4 at 1 700℃, the formation of more Al4O4C short fiber, and the formation of flake Al2O3 layer on suorface of the specimen.

Preparation of TiAl/Ti_2AlC Composites with Ti/Al/C Powders by In-situ Hot Pressing

TiAl/Ti2AlC composites were prepared by in-situ hot pressing of TilAl/C powders mixtures and sintered at different temperatures were investigated by X- ray diffraction （ XRD ） of samples. The reaction procedure of Ti-Al-C system could be divided into three stnges. Below 900℃ , Ti reacts with Al to form TiAl intermetallics ; above 900 ℃ , C reacts with remain Ti to form TiC triggered by the exothermal reaction of Ti and Al ; TiAl reacts with TiC to produce dense TiAl/Ti2AlC compasites.In the holding stage, ternary Ti2AlC develops to layered polycrystal and composites pyknosis in the meanwhile. The mechanism of synthesis and microstructure was especially discussed.

Research on the Surface Micro-configuration in Vibration Cutting Particle Reinforced Metallic Matrix Composites SiC_p/Al

The cutting performance of particulate reinforced me tallic matrix composites(PRMMCs) SiC p/Al in ultrasonic vibration cutting and c ommon cutting with carbide tools and PCD tools was researched in the paper. Mic rostructure of machined surface was described, the relation between cutting para meters and surface roughness was presented, and characteristic of the surface re mained stress was also presented. Furthermore, wear regularity and abrasion resi stance ability of tools in ultrasonic vibration cutting and common cutting o f PRMMCs were discussed in detail. The test results show: (1) The surface config urations are obviously different when using different tools to machine such PRMM Cs. The surface machined with carbide tools looks luminous and orderly and there are seldom surface defects on it. The reason is that the soft basal body is apt to flow during cutting, therefore a layer of Al matrix film covers machined sur face. On the contrary, the surface machined with PCD tools looks lackluster. But the profile of machined surface is very clear. Superfine grooves, pits and blac k reinforce particulates can be seen easily without obvious Al film. (2) Because of unstable cutting process in common cutting, the surface is easy to produce s ome defects such as burrs, built-up edges and so on so that the quality of surf ace becomes very poor. Vibration cutting can reduce the influence of tearing, pl astic deformation and built-up edge in cutting and can restrain flutter so as t o make cutting process more stable. Therefore, surface roughness of vibration cu tting is better than that of common cutting. (3) There is an optimum value of fe ed rate in vibration cutting of PRMMCs due to the influence of material characte ristics. Whether feed rate is more than or less than this optimum value, surface roughness will increase. (4) According to analyzing the wear rate of tools in v ibration cutting PRMMCs, it can be concluded that abrasion resistance of tools w ill be improved remarkably when vibration cutting composites have a lower pe rcentage of reinforce particulate. If the percentage of reinforce particulate is higher, the influence on abrasion resistance of carbide tool in vibration cut ting will not be obvious. The research result indicates that vibration cutting effect has a close relation with material characteristics.

三维编织C_(f)/Al复合材料T型件振动疲劳性能

采用真空压力浸渗法制备的三维编织C_(f)/Al复合材料具有良好的力学性能,在航空航天等领域的应用上具有较大潜力。本工作以三维编织C_(f)/Al复合材料为研究对象,对其在不同加载应力下进行振动疲劳实验,并观察疲劳实验后其断口处的微观结构。结果表明:加载应力越大,达到疲劳稳定阶段时T型件的固有频率降幅百分比也越大,即对T型件内部结构的破坏也越显著;对不同加载应力下的疲劳数据进行拟合,绘制S-N曲线,得到T型件振动疲劳损伤演变规律的数学模型,可用于预测三维编织C_(f)/Al复合材料的疲劳寿命;对实验后T型件进行断口处的宏观和微观分析,发现实验后的T型件呈现典型的脆性断裂特征。

基于Al-B-C烧结助剂的SiC_(nf)增强SiC陶瓷基复合材料制备及性能研究

以单晶碳化硅纳米纤维(SiC_(nf))为增强体,以铝(Al)粉、硼(B)粉和超细炭黑为烧结助剂,通过化学气相沉积及浸渍裂解工艺在SiC_(nf)上制备了PyC、BN双层界面包覆层,采用热压烧结法制备SiC_(nf)增强SiC陶瓷基复合材料(SiC_(nf)/SiC-CMC)。实验结果表明,Al-B-C烧结助剂在1850℃生成了液相Al8B4C7,促进了SiC陶瓷的致密化,提高了复合材料致密度。当烧结助剂含量为10wt.%时,随着Si Cnf含量的增加,复合材料内孔隙增多,致密度降低,抗弯强度和断裂韧性先增大后降低。当SiC_(nf)含量为10 wt.%时,复合材料的力学性能达到最优,抗弯强度和断裂韧性分别为414 MPa和9.65 MPa·m1/2,相较于未添加SiC_(nf)的热压烧结SiC陶瓷,其韧性提高了93.8%。微观结构分析表明,SiC_(nf)主要通过纤维拔出的方式来增加裂纹扩展时的能量消耗,达到提升陶瓷断裂韧性的效果。

Al-B_(4)C中子吸收材料的电化学腐蚀行为研究

【目的】研究Al-B_(4)C中子吸收材料的电化学腐蚀性能。【方法】采用球磨混粉-压力成型-真空烧结的方法制备了4种不同碳化硼含量的Al-B_(4)C复合材料,并对材料进行电化学腐蚀试验,腐蚀溶液为5%NaCl溶液。【结果】结果表明:碳化硼含量30%以下时,材料的耐腐蚀性能随着碳化硼含量的增加逐渐增强;碳化硼含量达到40%时,材料的耐腐蚀性迅速下降,且4种材料在各自电位区间发生了钝化现象。【结论】碳化硼含量10%时钝化现象最明显,材料腐蚀方式主要以点蚀为主。

Al填料改性PIP-2D SiC_(f)/SiC复合材料力学性能和电磁屏蔽性能

以Al粉为活性填料,采用先驱体浸渍裂解法(PIP法)制备二维连续碳化硅纤维增强碳化硅复合材料(2D SiC_(f)/SiC复合材料),采用XRD、SEM和热失重仪分析不同Al粉含量对聚碳硅烷裂解产物的组织成分演变行为,采用力学试验机和矢量网络分析仪研究不同Al粉含量对复合材料的力学及电磁屏蔽性能影响。结果表明:随着Al填料质量分数从0%增加至40%,复合材料弯曲强度先升高后下降,最高可达383 MPa;Al填料的引入使得复合材料复介电常数逐渐升高,电磁屏蔽效能逐渐增加至26 dB,得到了显著的提升,电磁屏蔽效能大幅度提升主要原因是Al填料含量增加引起复合材料复介电常数虚部显著增加。

Carbon-fiber-reinforced silicon carbide composites prepared by precursor pyrolysis-hot pressing

The Cf/SiC composites were prepared by precursor conversion-hot pressing sintering with AIN and Y2Os as additives. The effects of sintering temperature and additives on the microstructures and properties of the composites were investigated. The composite sintered at as low as 1 75O℃ already showed higher density and better mechanical properties, which was mainly attributed to the liquid-phase-sintering and the formation of the AIN-SiC solid solution. With increasing the sintering temperature to 1 800 ℃, the flexural strength and fracture toughness of the composite were substantially improved up to 691. 6 MPa and 2O. 7 MPa’ m1/2 respectively in spite of the slightly elevated density, and the composite exhibited "tough" failure. Despite the improved density, the composite sintered at 1 85O℃ displayed brittle failure, which mainly attributed to the strongly bonded fiber/matrix interface and the degradation of the properties of the fibers.

Effect of fiber characteristics on fracture behavior of C_f/SiC composites

C f/SiC composites were prepared by precursor pyrolysis hot pressing, and the effect of fiber characteristics on the fracture behavior of the composites was investigated. Because the heat treatment temperature of fiber T300 (below 1?500?℃) was much lower than that of fiber M40JB (over 2?000?℃), fiber T300 had lower degree of graphitization and consisted of more impurities compared with fiber M40JB, suggesting that T300 exhibits higher chemical activity. As a result, the composite with T300 showed a brittle fracture behavior, which is mainly ascribed to a strongly bonded fiber/matrix interface as well as the degradation of fibers during the preparation of the composite. However, the composite with M40JB exhibits a tough fracture behavior, which is primarily attributed to a weakly bonded fiber/matrix interface and higher strength retention of the fibers.

偏磷酸铝粘结剂在真空液相浸渗制备C_f/Al复合材料中的应用研究

采用真空压力浸渗工艺 ,以高强高模碳纤维M4 0J增强AlMg5为研究对象 ,研究了预制件抗压强度提高技术和高温粘结剂偏磷酸铝对复合材料中纤维平直度、复合材料性能的影响。结果表明 ,预制件中偏磷酸铝的加入使复合材料中纤维的平直度及分布的均匀性提高 ,用P Al 15∶1、浓度为 10wt%偏磷酸铝溶液处理后的预制件经真空液相浸渗后制得的复合材料 ,纤维不仅保持了较好的平直度 ,而且弯曲强度比未经粘结剂处理的提高近 10 2 %左右 ,达到5 35MPa。

偏磷酸铝在C_f/AL复合材料中的应用

以高模高强石墨纤维Ｍ４０Ｊ增强铝基复合材料为研究对象，研究了真空液相压渗工艺中，偏磷酸铝粘接剂对纤维预制件抗压性能及复合材料力学性能的影响。结果表明：偏磷酸铝的含量、Ａｌ／Ｐ原子比及处理温度对预制件的抗压性能均有显著影响，加入５％偏磷酸铝粘接剂溶液的预制件，经５００°Ｃ处理后的抗压性能满足压渗要求，纤维保持了较好的平直度及分布均匀性，所制备的复合材料抗拉强度大于５００ＭＰａ。

挤压力对真空吸渗挤压制备2D-C_f/Al复合材料的影响(英文)

碳纤维增强铝基复合材料(Cf/Al)具有众多优良性能,因而受到广泛重视和应用。采用一体化成形且能够保证高真空度和高浸渗压力的真空吸渗挤压工艺制备二维碳纤维增强铝基复合材料(2D-Cf/Al)。通过微观组织观察,研究不同挤压力(比压)下复合材料的浸渗质量,得到最佳的比压值。结果表明:采用该工艺能够制备出浸渗质量良好的Cf/Al复合材料,最佳比压为75MPa。此时,铝合金充填均匀,纤维损伤和铸造缺陷较少,浸渗情况良好,复合材料的力学性能最佳,其最大拉伸强度与基体合金相比提高138.9%。

Al_2O_(3f)+C_f/ZL109干摩擦磨损行为及其人工神经网络分析

采用挤压铸造法制备了氧化铝及碳短纤维混杂增强 Ｚ Ｌ１０９ 合金复合材料，考察了该复合材料的干摩擦磨损行为．结果表明：该复合材料的摩擦磨损性能随纤维总体积分数的增加而降低；当纤维总体积分数一定时，随碳纤维含量的增加复合材料摩擦磨损性能降低．采用人工神经网络技术对该复合材料的干摩擦磨损试验结果进行了综合分析，其结果与试验值吻合较好．分析表明：纤维总体积分数较小时，碳纤维含量对复合材料耐磨性的影响较大，随纤维总体积分数的增大其影响减弱；无论纤维总体积分数如何变化，碳纤维含量对复合材料摩擦系数均有较大影响，这是其自润滑作用的结果；载荷较小时，该复合材料摩擦磨损的跑合时间较长；随载荷的增大摩擦系数减小；

(Ti,Fe)-Al-C体系钢铁基复合材料的热力学计算与分析

利用溶液热力学理论,研究了(Ti,Fe)AlC体系钢铁基复合材料可能的反应产物的吉布斯自由能变化。热力学实验模型是在FeC熔液中加入钛铁合金(Ti,Fe)和纯铝块,继续加热到1600℃,熔液经过充分混合、反应后随炉冷却到常温。计算结果表明,TiC先于Fe2Ti、Fe3C等相生成,但始终没有Al4C3和TiAl3相产生;体系中TiC的热力学稳定性最高;在凝固过程中,TiC相优先析出,随后可能有Fe2Ti、Fe3C等相析出;铝含量的增加能够促进TiC、Fe2Ti、Fe3C等相的生成。

短纤维取向对Al_2O_(3f)+C_f/ZL109复合材料干滑动摩擦磨损性能的影响

利用挤压铸造法制备了 Al2 O3 f+Cf/ZL10 9短纤维混杂金属基复合材料 ,并利用统计学方法对比研究了在滑动速度 0 .837m/s、载荷 196 N条件下纤维取向对该混杂复合材料干滑动摩擦磨损性能的影响 .结果表明 :在纤维平行取向和垂直取向时 ,该混杂复合材料的磨损率和摩擦系数均服从正态分布 ;平行取向情况下磨损率均值大于垂直取向下的磨损率 ,而摩擦系数均值小于垂直取向 ;纤维垂直取向有利于复合材料耐磨性能的提高 。

应变率对C_f/Al金属基复合材料力学性能的影响

利用自行研制的冲击拉伸试验装置对单向碳纤维增强铝基复合材料实施了不同应变率下的拉伸试验 ,获得了材料从 0 .0 0 1s- 1 到 10 0 0 s- 1 应变率范围内完整的应力应变曲线。试验结果表明 Cf/ Al是一种应变率敏感材料 ,随着应变率的提高 ,材料的拉伸强度、失稳应变均相应提高 ,具有明显的应变率强化效应和动态韧性现象。根据材料在不同应变率下的试验结果 ,提出了应变率强化效应的复合丝束统计本构模型 ,模型分析表明由于复合材料的破坏受多种因素的影响 ,Cf/ Al复合丝的强度不再服从单 Weibull模型 ,用双 Weibull模型更能反映 Cf/ Al复合丝强度的统计分布规律 ,且模型拟合的结果与试验结果吻合得很好。