SiC_p/2024Al基复合材料的点蚀形貌

用扫描电镜对浸泡在w(NaCl)=3 5%水溶液中的SiCp/2024Al金属基复合材料(AlMMCs)的点蚀形貌进行了观察,作为对比,对其基体合金的点蚀行为也进行了研究·结果表明,SiCp/2024AlMMCs的点蚀形貌与SiC颗粒的体积分数和尺寸有关,SiC含量高或尺寸小的AlMMCs,其蚀孔数量较多,尺寸较小·与基体合金相比,AlMMCs的点蚀孔较大,数量较少,分布也较不均匀,甚至出现局部严重腐蚀的现象·能谱分析表明,SiCp/2024AlMMCs的腐蚀机制为富Cu阴极相与贫Cu阳极相间的电偶腐蚀·另外,SiC与Al间也存在电偶腐蚀倾向·     

Al_2O_3/SiC纳米陶瓷复合材料的制备及力学性能

采用一次粒径分别为10nm和15nm的αAl2O3和SiC粉体为原料,制备了Al2O3/SiC纳米陶瓷复合材料·纳米SiC颗粒明显抑制Al2O3基体晶粒的长大,SiC体积分数超过4%时,材料的断裂方式由沿晶断裂变为穿晶断裂·随SiC含量的增加,Al2O3/SiC纳米复合材料的硬度增大·材料的弯曲强度和断裂韧性在SiC体积分数为5%时达到最大值·最大三点弯曲强度和断裂韧性分别为641MPa和47MPam1/2,明显高于热压单相Al2O3陶瓷(344MPa和31MPam1/2)·复合材料的强化主要来源于内晶颗粒残余应力强化和晶粒细化...     

纳米SiCp/108Al复合材料的组织与性能

采用粉末冶金法制备了不同体积分数SiC颗粒增强的纳米SiCp/108Al复合材料。利用光学显微镜、扫描电子显微镜、透射电子显微镜对复合材料的微观组织及拉伸断口形貌进行了表征,测定了复合材料的相对密度、硬度、抗拉强度、屈服强度及延伸率,分析了纳米SiC颗粒体积分数对复合材料组织及性能的影响。分析结果表明:添加纳米SiC颗粒的SiCp/108Al复合材料组织明显细化,性能得到提高。当纳米SiC颗粒体积分数为2%时,复合材料组织的晶粒最细小,缺陷较少,同时纳米SiC颗粒分布均匀,复合材料的性能最佳,相对密度达到98%。复合材料的硬度达到102HV,抗拉强度达到348MPa,屈服强度达到229MPa,分别比108Al基体提高了34%、26%和43%。当纳米SiC颗粒体积分数较大时,SiC颗粒会出现明显团聚现象,导致复合材料的性能降低。     

纳米SiC颗粒复合对Al2O3_ZrO2陶瓷材料力学性能的影响

研究了纳米SiC颗粒复合对Al2O3—ZrO2陶瓷材料力学性能影响的两个因素，即ZrO2的相变强韧化和纳米SiC颗粒的弥散强韧化。实验发现，处于晶界的纳米SiC颗粒，有松弛晶界应力的作用，使得样品中在室温下保留的四方相含量减少，ZrO2的相变强韧化作用减小，但纳米SiC颗粒在晶界处对裂纹的钉扎作用又改善了材料的力学性能。如果两个因素能协调作用，将会使强韧化效果增大，反之则会降低。     

SiC/PTFE纳米复合材料定量分析方法

为对SiC/PTFE纳米复合材料微观结构进行定量分析,运用自主开发的、基于图像处理技术的纳米复合材料微观结构分析系统,用颗粒分散度计算方法,对SiC/PTFE纳米复合材料微观结构进行了计算和分析.结果表明：颗粒分散度能较好地定量表征纳米粒子在PTFE基体中分散的均匀性;随着SiC纳米粒子含量增加,颗粒分散度先增大后减小;SiC纳米粒子含量为7%时,颗粒分散度较高,复合材料中纳米粒子分散较均匀;偶联剂处理可以提高SiC纳米粒子在PTFE基体中颗粒分散度.     

颗粒失效对SiCp/Al复合材料强度的影响

建立复合材料屈服强度综合模型用于分析研究增强颗粒断裂和基体与颗粒的界面脱粘对SiCp／Al复合材料强度的影响;用Eshelby等效夹杂理论分析SiCp/Al复合材料受载时作用在SiC颗粒上的应力,并假设SiC颗粒失效符合Weibull分布,在综合考虑复合材料各种强化机制的基础上引入颗粒断裂和界面脱粘对材料屈服强度的影响,建立SiCp／Al复合材料的屈服强度模型并对模型进行解析。研究结果表明：SiCp/Al复合材料屈服强度随着SiC颗粒含量增加而增加;当颗粒粒度为微米级时,屈服强度随着粒度的减小而增加;在屈服状态下,当颗粒粒度较小时,复合材料的颗粒失效以界面脱粘为主;随着粒度的增大,颗粒的断裂分数迅速增大,颗粒失效则转变为由颗粒断裂和界面脱粘共同控制。     

纳米颗粒填充聚四氟乙烯基复合材料的分散性表征

对纳米Si3N4、AlN和SiC颗粒填充聚四氟乙烯（PTFE）基复合材料表面形貌的扫描电子显微镜(SEM)图像进行处理与分割,利用颗粒分散度方法表征分割图像中纳米颗粒的团聚程度和分散性.结果表明：在3种纳米颗粒填充PTFE基复合材料中,纳米SiC的分散性最佳,纳米AlN的分散性最差;当纳米Si3N4和SiC的质量分数为7%、纳米AlN的质量分数为5%时,PTFE基复合材料的分散性较好;经钛酸酯偶联剂处理后,可使纳米Si3N4和SiC在PTFE基复合材料中的分散性提高,但会使纳米AlN在PTFE基复合材料中的分散性下降.     

45#钢表面Ni-P-nano-SiC复合化学镀层的制备

在优化设计的化学镀基础镀液中通过添加不同含量的纳米SiC颗粒,研究在45#钢表面制备具有纳米SiC颗粒增强的复合镀层及形成机理.利用SEM,XRD和显微硬度计等方法对实验样品的组织结构、形貌、显微硬度及其镀层形成机理进行了研究,结果表明:实验制备的Ni-P,Ni-P-SiC镀层镀态时硬度分别为572 HV,649 HV,热处理后其表面硬度在400℃时达到最大值1 045 HV和1 341 HV.纳米SiC颗粒在镀液中不参与化学反应,只是与化学反应所产生的Ni和P共同沉积在镀层中起到了复合强化的作用.Ni-P-nano-SiC镀层的生长机理是按层状方式生长,生长方向垂直于钢基体表面.纳米SiC提...     

6066Al/SiCP复合材料的组织特征与阻尼性能

研究了经制粉→混料→真空抽气→热挤压工艺制备的6066Al/SiCp复合材料的组织特征与阻尼性能.复合材料的阻尼特征通过动态机械热分析仪(DMTA)测量,得出了2种不同SiC含量的6066Al/SiCp复合材料及6066Al合金在温度为30～250℃,频率为0.1,1,10和30Hz时的阻尼值.利用扫描电镜、光学显微镜对复合材料组织特征进行了分析,根据组织特征及阻尼数据对复合材料的阻尼机制进行了讨论.结果表明将2～3μm的SiC颗粒加入6066Al中,当SiC含量为7%(体积分数)时,增强的SiC颗粒分布较均匀,与基体结合良好;当SiC含量为12%时,SiC易聚集成团.少量SiC能明显提高6066Al的阻尼能力,尤其是高温阻尼性能;6066Al/SiCp复合材料的高阻尼性能主要是SiC颗粒加入后使位错密度大大增加,基体晶界及基体与SiC颗粒界面的存在使材料在循环载荷下消耗能量所致.     

颗粒弥散强化复相陶瓷

制备SiC、TiB2 及ZrO2 颗粒弥散强化MoSi2 、Al2 O3基复相陶瓷 ,研究了弥散颗粒及其加入量对材料强韧化效果的影响 ,并探讨了弥散颗粒多重强化协调作用及机理 结果表明 :弥散颗粒的加入量对材料的强韧性有显著影响 ;通过合理的工艺控制 ,不仅在ZrO2 、TiB2 二元颗粒复合弥散强化的Al2 O3基复相陶瓷中 ,而且在单相ZrO2 颗粒弥散强化的MoSi2 基复相陶瓷中 ,弥散颗粒均实现了相变强化与弥散强化双重作用     

Enhanced performance of nano-sized SiC reinforced Al metal matrix nanocomposites synthesized through microwave sintering and hot extrusion techniques

In the present study, nano-sized SiC (0, 0.3, 0.5, 1.0 and 1.5 vol%) reinforced aluminum (Al) metal matrix composites were fabricated by microwave sintering and hot extrusion techniques. The structural (XRD, SEM), mechanical (nanoindentation, compression, tensile) and thermal properties (co-efficient of thermal expansion- CTE) of the developed Al-SiC nanocomposites were studied. The SEM/EDS mapping images show a homogeneous distribution of SiC nanoparticles into the Al matrix. A significant increase in the strength (compressive and tensile) of the Al-SiC nanocomposites with the addition of SiC content is observed. However, it is noticed that the ductility of Al-SiC nanocomposites decreases with increasing volume fraction of SiC. The thermal analysis indicates that CTE of Al-SiC nanocomposites decreases with the progressive addition of hard SiC nanoparticles. Overall, hot extruded Al 1.5 vol% SiC nanocomposites exhibited the best mechanical and thermal performance as compared to the other developed Al-SiC nanocomposites.     

Mechanical and microstructural characterization of Al7075/SiC nanocomposites fabricated by dynamic compaction

This paper describes the synthesis of Al7075 metal matrix composites reinforced with SiC, and the characterization of their microstructure and mechanical behavior. The mechanically milled Al7075 micron-sized powder and SiC nanoparticles are dynamically compacted using a drop hammer device. This compaction is performed at different temperatures and for various volume fractions of SiC nanoparticles. The relative density is directly related to the compaction temperature rise and indirectly related to the content of SiC nanoparticle reinforcement, respectively. Furthermore, increasing the amount of SiC nanoparticles improves the strength, stiffness, and hardness of the compacted specimens. The increase in hardness and strength may be attributed to the inherent hardness of the nanoparticles, and other phenomena such as thermal mismatch and crack shielding. Nevertheless, clustering of the nanoparticles at aluminum particle boundaries make these regions become a source of concentrated stress, which reduces the load carrying capacity of the compacted nanocomposite.     

Fabrication of homogeneously dispersed graphene/Al composites by solution mixing and powder metallurgy

Graphene-reinforced aluminum (Al) matrix composites were successfully prepared via solution mixing and powder metallurgy in this study. The mechanical properties of the composites were studied using microhardness and tensile tests. Compared to the pure Al alloy, the graphene/Al composites showed increased strength and hardness. A tensile strength of 255 MPa was achieved for the graphene/Al composite with only 0.3wt% graphene, which has a 25% increase over the tensile strength of the pure Al matrix. Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and transmission electron microscopy were used to investigate the morphologies, chemical compositions, and microstructures of the graphene and the graphene/Al composites. On the basis of fractographic evidence, a relevant fracture mechanism is proposed.     

Aluminum matrix composites reinforced by molybdenum-coated carbon nanotubes

To extend the application of carbon nanotubes (CNTs) and explore novel aluminum matrix composites, CNTs were coated by molybdenum layers using metal organic chemical vapor deposition, and then Mo-coated CNT (Mo-CNT)/Al composites were prepared by the combination processes of powder mixing and spark plasma sintering. The influences of powder mixing and Mo-CNT content on the mechanical properties and electrical conductivity of the composites were investigated. The results show that magnetic stirring is better than mechanical milling for mixing the Mo-CNTs and Al powders. The electrical conductivity of the composites decreases with increasing Mo-CNT content. When the Mo-CNT content is 0.5wt%, the tensile strength and hardness of Mo-CNT/Al reach their maximum values. The tensile strength of 0.5wt% Mo-CNT/Al increases by 29.9%, while the electrical conductivity only decreases by 7.1%, relative to sintered pure Al. The phase analysis of Mo-CNT/Al composites reveals that there is no formation of Al carbide in the composites.     

SiC_p/2024Al铝基复合材料表面颗粒暴露及真空钎焊分析

采用复合材料表面颗粒暴露及表面合金化工艺,利用M6和BAI88S i钎料对S iCp/2024A l铝基复合材料进行钎焊试验,并进行金相分析、拉伸试验和X射线衍射试验。结果表明:采用(NaOH+HNO3)工艺能将复合材料表面颗粒部分暴露出来;采用表面沉积Cu,使用M6钎料,能改善钎缝的结合状态;钎缝与铝基复合材料间无明显界限,结合良好,并形成了有S iC颗粒增强的复合钎缝,S iC颗粒在钎缝中无团聚现象;钎焊接头强度能达到202 MPa;在钎缝中无A l4C3脆性相生成。     

Al_2O_3／nano－SiC复相陶瓷力学性能及显微结构

研究了热压烧结Ａｌ２Ｏ３／ｎａｎｏ－ＳｉＣ复相陶瓷的力学性能及显微结构。研究表明,纳米ＳｉＣ的引入显著地改善了材料的力学性能,在ＳｉＣ添加体积分数为１０％时,Ａｌ２Ｏ３／ｎａｎｏ－ＳｉＣ复相陶瓷抗弯强度σｆ达峰值为８６９ＭＰａ,断裂韧性ＫＩｃ也达峰值为６．７ＭＰａ·ｍ０．５,比纯Ａｌ２Ｏ３基体材料分别提高１３８％和８１％。ＴＥＭ观察表明：纳米ＳｉＣ晶粒主要存在于Ａｌ２Ｏ３基体晶粒内部,形成独特的“晶内型”结构。当受外力作用时,既能因弥散的纳米颗粒诱发穿晶断裂,且穿晶断裂时,还能因晶内存在第二相颗粒而引起裂纹偏转,起到增强增韧作用。     

碳化硅粒子增强铝基复合材料的研制

论述了ＳｉＣ粒子增强铝基复合材料的制备工艺,探讨了不同ＳｉＣ粒子加入量对材料物理性能、力学性能、磨损性能等的影响．结果表明,ＳｉＣ粒子的加入降低了材料的密度和热膨胀系数,但大大提高了材料的耐磨性能;复合材料与基体合金相比,抗拉强度有所下降．     

SiCp/Al MMCs等离子弧原位焊接接头组织与性能

通过填充Ti,N元素对SiCp／Al基复合材料（SiCp／Al MMCs）进行等离子弧原位焊接,分析了焊缝的组织和力学性能．以氩、氮混合气体为离子气,0．8mm厚钛片作为原位合金化材料进行原位焊接,不仅抑制了脆性相的形成,而且在焊缝中形成了TiN,TiC等新的增强相,保证了焊接接头的性能．力学性能试验结果表明,不加填充材料焊接时,试样拉伸强度仅为母材强度的31．24％;进行原位焊接时,试样强度达到母材强度的50．89％．断口主要表现为混合型脆性断口．     

Investigation on microstructural, mechanical and electrochemical properties of aluminum composites reinforced with graphene nanoplatelets

In present study, the microstructure, mechanical and electrochemical properties of aluminum–graphene nanoplatelets (GNPs) composites were investigated before and after extrusion. The contents of graphene nanoplatelets (GNPs) were varied from 0.25 to 1.0 wt.% in aluminum matrix. The composites were fabricated thorough powder metallurgy method, and the experimental results revealed that Al-0.25%GNPs composite showed better mechanical properties compared with pure Al, Al-0.50%GNPs and Al-0.1.0%GNPs composites. Before extrusion, the Al-0.25%GNPs composite showed ~13.5% improvement in ultimate tensile strength (UTS) and ~50% enhancement in failure strain over monolithic matrix. On the other hand, Al-0.50%GNPs and Al-0.1.0%GNPs composites showed the tensile strength lower than monolithic matrix. No significant change was observed in 0.2% yield strength (YS) of the composites. However, the extruded materials showed different trends. The 0.2%YS of composites increased with increase in GNPs filler weight fractions. Surprisingly, UTS of composites with 0.25 and 0.50% GNPs was lower than monolithic matrix. The failure strain of the baseline matrix was enhanced by ~46% with 0.25% graphene nanoplatelets. The superior mechanical properties (in terms of failure strain) of the Al-0.25%GNPs composite maybe attributed to 2-D structure, high surface area and curled nature of graphene. In addition, the corrosion resistance of pure Al and its composites reinforced with 0.5 and 1.0 wt% GNPs was also investigated. It was found that the corrosion rate increased considerably by the presence of GNPs.