Fabrication and mechanical properties of MWCNTs-reinforced aluminum composites by hot extrusion

Over the past decade,the interest in aluminum composites reinforced with carbon nanotubes has grown significantly.Studies have been carried out to overcome problems with uniform dispersion,interfacial bonding,void formation and carbide formation of the composites.In the present work,multi-wall carbon nanotubes(MWCNTs)aluminum composites were produced.High-energy ball milling with the aim at developing well-dispersed MWCNTs Al composites was followed by cold compaction,sintering,and hot extrusion at 500 ℃.Different amounts of stearic acid as processing control agent(PCA)is used in order to minimize cold welding of the Al particles,and to produce finer particles.Differential scanning calorimetry(DSC),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and X-ray diffraction(XRD)were employed to analyze the MWCNTs,the aluminum powder,and the composites' microstructural behavior.The hardness and tensile properties of the composites are also evaluated.The results showed 500％ increase in yield stress after the addition of 1 wt％ MWCNTs in Al-MWCNTs based composite.The ball-milling time of 4 h is found to be sufficient as excessive milling time destroys a vast number of MWCNTs.     

CNTs含量对CNTs/Al5083复合材料力学性能的影响

利用高能球磨和冷压烧结工艺制备出碳纳米管（CNTs）增强Al5083复合材料,并对球磨过程中CNTs的演变及成型后复合材料的力学性能和形貌进行研究。结果表明,在球磨过程中,通过机械力的作用下带动钢球将CNTs切断,长径比变小,并均匀地分散在Al基体中;在CNTs含量为2wt%下,复合材料抗拉强度和屈服强度分别达到294和239 MPa,硬度达到95 HV5,复合材料的力学性能最好。通过观察复合材料的断口,随着碳纳米管含量的增加,复合材料的断口形貌从韧性断裂向脆性断裂转变。     

碳纳米管-银复合材料力学性能研究

采用粉末冶金方法制备碳纳米管-银复合材料，研究了碳纳米管的含量对碳纳米管-银复合材料的硬度、抗弯强度影响。实验表明：当碳纳米管的含量小于11％时，复合材料的密度、硬度较好，碳纳米管起到了增强作用；当碳纳米管的含量大于11％时，由于碳纳米管的团聚，导致复合材料密度、硬度迅速下降；由于碳纳米管和银的弱界面结合，以及碳纳米管在拉应力条件下载荷传递的效力比在压应力时低，使得碳纳米管对复合材料抗弯强度的增加不明显。     

含微纳B4C/Ti颗粒铜基复合材料的微观组织与力学性能

采用高能球磨(HEBM)和放电等离子烧结(SPS)工艺成功制备出微纳B₄C/Ti颗粒增强铜基复合材料(CTBCs),通过X射线衍射(XRD)、光学显微镜(OM)、扫描电子显微镜(SEM)以及能谱(EDS)等测试手段对其微观组织形貌进行表征。结果表明,(B₄C+Ti)颗粒在基体中均匀分布,增强体与铜基体界面结合良好,且其结合形式为冶金结合和机械结合并存。采用阿基米德排水法测定出烧结态试样的致密度。复合材料的显微硬度、拉伸屈服强度、抗拉强度和延伸率等力学性能相较于纯铜试样得到显著提高,这主要归因于载荷传递、细化晶粒与热错配等强化机制。复合材料的拉伸断口表现出明显的韧性断裂特征。     

高能球磨法制备钨铜复合材料研究

用机械搅拌及高能球磨法制备W-15wt%Cu复合粉,对其预压成型后采用两步烧结。用X射线衍射对比分析了球磨后钨铜复合粉与原始钨、铜粉的衍射峰变化,用扫描电子显微镜对所制备的复合粉及烧结钨铜复合材料进行了组织形貌观察,并测定了烧结复合材料的相对密度。结果显示球磨钨铜复合粉的晶粒尺寸得到细化,且有不饱和固溶体产生,其烧结合金组织均匀,相对密度增大。     

高能球磨结合粉末冶金法制备碳纳米管增强7055Al复合材料的微观组织和力学性能

采用高能球磨结合粉末冶金工艺制备了碳纳米管(CNT)含量(体积分数)分别为0、1%和3%的CNT/7055Al复合材料。采用OM、SEM、TEM以及拉伸实验等方法研究了CNT/7055Al复合材料的CNT分布、晶粒结构、近界面结构及力学性能,分析了复合材料的强化机制和各向异性。结果表明,CNT/7055Al复合材料为无CNT的粗晶区与富集CNT的超细晶区组成的双模态晶粒结构;CNT在Al基体的超细晶区中分散良好,CNT-Al界面干净清洁,界面反应产物少;3%CNT/7055Al复合材料沿挤压方向的抗拉强度达到816 MPa,但延伸率仅为0.5%。细晶强化和Orowan强化是CNT/7055Al复合材料主要的强化机制。由于CNT沿不同方向的增强效率不同以及粗晶条带组织的存在,复合材料表现出比基体合金更强烈的各向异性,在垂直挤压方向的拉伸性能要弱于沿挤压方向的拉伸性能。     

Mechanical and electrical properties of carbon nanotube reinforced epoxide resin composites

Carbon nanotubes （CNTs）/epoxide resin composites were prepared, the mechanical and electrical properties of the composites were investigated. The effects of concentration and dispersion state of CNTs on the tensile strength, tensile modulus and electrical resistance of the composites were studied. The results indicate that the CNTs can be dispersed well in the epoxide resin matrix by ultrasonic method, and the mechanical and electrical properties of epoxide resin matrix can be improved significantly. The tensile tests show that the tensile strength and tensile modulus are higher than those of epoxide resin if the content of CNTs is less than 1.75% （mass fraction）. When the content of CNTs is 0.75%, the conditional best results are obtained, the tensile strength of the composite is the highest, increased by 18.3% and the tensile modulus is increased by 20.5% compared with the matrix. With the increase of CNTs, the electrical resistance of the composites decreases greatly, while the conductivity of the composite increases. The percolation threshold values of electrical characteristic transformation for this composite material were determined for the first time.     

CNTs/AgCuNi复合材料的制备及力学性能

银基复合材料具有高强度、高模数、低延展性、高耐磨性、低热膨胀等优异性能,在电接触领域中迅速发展。本研究采用机械合金化法将CNTs与AgCuNi合金粉末混粉、球磨,将复合粉末通过放电等离子(SPS)压制烧结后制备出CNTs/AgCuNi银基复合材料。研究了添加不同体积分数CNTs及不同压制烧结温度制备的复合材料组织结构、力学性能。结果表明,添加2%的CNTs的复合材料在700 ℃烧结后,材料致密度达到98.93%、硬度(HV0.2)为101.07,综合性能较好。     

球磨方式对多壁碳纳米管形貌和结构的影响

对多壁碳纳米管(MWNTs)分别进行干式球磨和湿式球磨,采用TEM、XRD、XPS和Raman光谱等方法分析球磨对MWNTs形貌和结构的影响。结果表明：MWNTs在磨球的冲击作用下产生弯曲、扭结,形成结构缺陷;MWNTs容易在缺陷处断裂,产生大量敞开的断口,这些断口形态可发生转化;与干式球磨比较,湿式球磨后MWNTs的长度较平均,多数端部处于敞开状态,且其结构的损坏程度较小;MWNTs的分散状态及其断口结构的稳定性是影响球磨效果的重要因素。     

球磨法和搅拌铸造法制备SiCp/Al复合材料

用高能球磨法制备出SiC-Al复合粉体,再把复合粉体搅拌弥散到Al熔液中,浇铸制得0.5%、1.0%、1.5%质量分数,下同)SiCp/Al复合材料.制备出的复合材料与未经增强的铝材相比,其抗拉强度分别提高:46.8%、63.8%、34.0%,硬度分别提高:99.1%、116.1%、67.9%.在SiC添加质量分数相同的情况下,添加复合粉的浇铸体与直接添加SiC粉体的浇铸体相比,前者的抗拉强度和硬度高于后者,说明SiC粉和Al粉复合后更容易弥散到Al熔液中.     

铸造法制备CNTs／AM60镁基复合材料的研究

采用搅拌铸造法制备了CNTs/AM60镁基复合材料,研究了搅拌法加入碳纳米管的工艺特点,测试了复合材料的力学性能,并利用扫描电子显微镜和能谱分析对复合材料断口形貌进行观察和分析。研究结果表明,碳纳米管能细化复合材料晶粒组织,且起搭接晶粒和承载变形抗力作用。与基体合金相比,复合材料抗拉强度、弹性模量、显微硬度显著增加,伸长率最大可提高74.52%,但是碳纳米管加入量过多会导致偏聚,使力学性能下降。     

Effects of Binder Phase Content and Substrate Hardness on Deposition Behavior of Cermet Particles in Cold Spraying Process

In this paper,three kinds of cermet particles with different binder phase and content,namely WC-12Co,WC-17Co and Cr3C2-25NiCr were deposited on the Q235 low carbon steel and WC-12Co coating substrates to investigate the effect of binder phase content and substrate hardness on deposition behavior of cermet particle during cold spraying.The morphology of the deposited particles was examined by scanning electron microscopy(SEM)from the particle surface and cross-sections.It was found that with increasing substrate hardness,the deposition behavior of cermet particles transformed from completely embedding into substrate to partially flattening and even rebounding.Varying the Co content from 12 wt%to 17 wt% influenced significantly the deposition deformation behavior of the WC-Co particles,the higher Co content brought about a fuller flattening of WC-Co particles.However,Cr3C2-25NiCr particle exhibited the relatively lower flattening ratio and significant rebounding of Cr3C2 even with the highest binder phase content,which may be attributed to the bigger Cr3C2 size and weak bonding between Cr3C2 and NiCr.     

Microstructure Characteristics of SiC Particle-Reinforced Aluminum Matrix Composites Coatings by Cold Spraying

A dense Al/SiCp composite coating with high volume fraction(60%)of nano SiCp reinforcement was fabricated by cold spraying of ball-milled Al-60SiCp composite powder.The morphologies evolution of the Al-60SiCp composite powder during ball milling and the microstructure and microhardness of the cold-sprayed Al-60SiCp composite coating were investigated.The results show that Al particles undergone fracture deformation and nano SiC particles are uniformly distributed in soft Al matrix after ball milling.A dense Al-60SiCp composite coating can be fabricated by cold spraying of ball milled composite powder.Nano SiC particles in the cold-sprayed Al-60SiCp composites coating exhibit a reasonably uniform distribution.The Hv0.5 microhardness of the Al-60SiCp composite coating is reached up to(5.30±0.53)GPa due to the enhancement of SiC particles,compared to(0.34±0.03)GPa for the pure Al bulk.     

碳纳米管在与铜粉混合球磨过程中的形态演化

分别将直径小于2 nm的单壁碳纳米管(单壁管含量为50%),直径8~10 nm的多壁碳纳米管和直径80~100 nm的多壁碳纳米管与铜粉混合,并进行机械球磨,用SEM和TEM对球磨过程中碳纳米管的形态演变进行研究。结果表明：直径80~100nm的碳纳米管在受到机械冲击时以发生断裂为主,而在形态上依然保持碳管的基本结构;其断口有开口和封口两种结构,在开口处具有比较复杂的微观结构且存在大量的赘生管;直径小于10 nm的碳纳米管在机械球磨过程中则易形成球状的缠结、纳米碳颗粒和巴基葱;这种差异与不同直径的碳纳米管中不饱和化学键所占的比例有关。     

Fe-Al复合粉在高能球磨时的组织转变及真空烧结的FeAl基合金的力学性能研究

研究了机械球磨与真空烧结制备FeAl基合金的工艺——球磨过程中Fe-Al粉末的结构转变及FeAl基烧结体的微观结构和力学性能。结果表明,Fe、Al单质混合粉末经机械球磨可得到具有Fe、Al相间层片结构的复合粉,且球磨时间越长,Fe、Al复合粉的层片结构越薄越均匀。FeAl基材料优异的室温力学性能与晶粒细化、组织均化效应有关。     

Fe-Al复合粉在高能球磨时的组织转变及真空烧结的FeAl基合金的力学性能研究

研究了机械球磨与真空烧结制备FeAl基合金的工艺——球磨过程中Fe-Al粉末的结构转变及FeAl基烧结体的微观结构和力学性能。结果表明，Fe、Al单质混合粉末经机械球磨可得到具有Fe、Al相间层片结构的复合粉，且球磨时间越长，Fe、Al复合粉的层片结构越薄越均匀。FeAl基材料优异的室温力学性能与晶粒细化、组织均化效应有关。     

SiC_p/ZL201复合材料的力学性能

研究了ＳｉＣｐ尺寸、含量及热处理工艺对铸造ＳｉＣｐ／ＺＬ２０１复合材料的室温和高温力学性能的影响。随ＳｉＣｐ含量的提高和粒子尺寸的增大,复合材料的室温抗拉强度呈下降趋势。随温度升高,基体合金的抗拉强度急剧下降,而复合材料的则下降较小。当温度大于２４０℃时复合材料的抗拉强度高于基体合金,表明ＳｉＣｐ的加入显著提高了基体合金的高温抗拉强度。     

钨增强块体非晶复合材料的研究进展

钨增强块体非晶复合材料属于一种新型材料,具有高强度、高硬度和耐磨损等优质性能,而且还具有非常优越的穿甲性能,在国防军事上有广阔的应用前景.所以国内外学者对钨增强块体非晶复合材料的制备方法、准静态和动态的力学性能和侵彻穿甲方面进行了广泛的研究,研究表明,钨增强块体非晶复合材料的性能与增强相钨的形态、体积分数、直径、环境温...     

浸渍-碳化工艺对碳/碳复合材料力学性能的影响

采用碳纤维针刺整体毡作为增强体,硼酚醛树脂作为基体先驱体,用浸渍碳化的方法制备C/C复合材料.考察了在不同的浸渍压力和碳化温度下材料力学性能的差异.分析结果表明:不仅密度是影响碳/碳复合材料力学性能的重要因素,纤维和基体的结合状况以及基体碳的结构也是决定材料强度和断裂方式的重要因素.随着工艺参数的改变,碳/碳复合材料的断裂模式可以由“假塑性断裂”向“脆性断裂”转变.