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。     

Effect of coating thickness on microstructures and mechanical properties of C/Cu/Al composites

The different copper coatings with thickness varying from 0.3 lain to 1.5 lain were deposited on carbon fibers using either eleetroless plating or electroplating method. The coated fibers were chopped and composites were fabricated with melting aluminum at 700 ℃. The effect of the copper layer on the microstructure in the system was discussed. The results show that the copper layer has fully reacted with aluminum matrix, and the intermetallic compound CuAl2 forms through SEM observation and XRD, EDX analysis. The results of tensile tests indicate that composites fabricated using carbon fibers with 0.7-1.1 lain copper coating perform best and the composites turn to more brittle as the thickness of copper coating increases. The fracture surface observation exhibits good interface bonding and ductility of the matrix alloy when the thickness of copper coating is about 0.7-1.1 μm.     

碳纳米管铜基复合材料的制备

利用CVD法制备多壁碳纳米管，并对其进行亲水化表面处理。在存在表面活性剂的情况下，利用共沉积法制备碳纳米管一超细铜粉复合粉体。复合粉体经还原后，采用冷压烧结、六面顶热压、真空热压烧结和真空热压后热轧4种不同工艺成型。利用SEM和XRD比较了这几种工艺成型的复合材料结构和被氧化的情况。结果表明，采用真空热压后热轧工艺制备的碳纳米管铜基复合材料的致密度较高且能有效地防止被氧化。     

Microstructures and mechanical properties of BP/7A04 Al matrix composites

The microstructures and interface structures of basalt particle reinforced 7A04 Al matrix composites (BP/7A04 Al) were analyzed by using OM, TEM, SEM and EDS, and the mechanical properties of 7A04 Al alloy were compared with those of BP/7A04 Al matrix composites. The results show that the basalt particles are dispersed in the Al matrix and form a strong bonding interface with the Al matrix. SiO₂ at the edge of the basalt particles is continuously replaced by Al₂O₃ formed in the reaction, forming a high-temperature reaction layer with a thickness of several tens of nanometers, and Al₂O₃ strengthens the bonding interface between basalt particles and Al matrix. The dispersed basalt particles promote the dislocation multiplication, vacancy formation and precipitation of the matrix, and the precipitated phases mainly consist of plate-like η (MgZn₂) phase and bright white band-shaped or ellipsoidal T (Al₂Mg₃Zn₃) phase. The bonding interface, high dislocation density and dispersion strengthening phase significantly improve the mechanical properties of the composites. The yield strength and ultimate tensile strength of BP/7A04 Al matrix composites are up to 665 and 699 MPa, which increase by 11.4% and 10.9% respectively compared with 7A04 Al alloy without basalt particles.     

Microstructures of electron beam welding joint of CNTs/ Al composites

Carbon nanotube(CNT) reinforced aluminum metal matrix composites were welded by electron beam welding and the microstructures of welded joints were investigated.The result showed that the interfacial reaction happened between the CNTs and Al matrix,which resulted in producing brittle Al4C3 compounds in electron beam welds.The extent of interfacial reaction varies gradually in the depth and width direction.The length of the reactants Al4C3 became short duo to the temperature gradient in the molten pool.The quantity and size of Al4C3 compounds increased with the increase of beam current and the decrease of welding speed in the middle zone of weld.However,no needle-like phase Al4C3was observed in HAZ.     

两相连续网络结构Ti2AlC/TiAl复合材料的制备及力学性能

采用热压工艺制备不同体积分数的Ti2AlC/TiAl复合材料,并研究其增强结构特征及力学性能.当增强相体积分数达到20％时,复合材料形成两相三维互贯通的结构;当增强相体积分数高于20％,复合材料中Ti2AlC相聚集长大并形成粗大的骨骼网络.Ti2AlC相的微观塑性变形行为(如扭折和层裂)能改善复合材料的断裂韧性,均匀细...     

Influence of heat treatment on microstructure and mechanical properties of Al/Al-Cu graded materials

Five-layered Al/Al-Cu functionally graded material (FGM) was prepared by powder metallurgy technology, and the subsequent heat treatment was carried out for the graded material. The microstructures and distribution of Cu element under pressure sintering (F), solution treatment (T4) and artificial aging treatment (T6) were investigated, and the Vickers hardness and flexural properties of different states were tested. The results showed that sintered compact with dense structure and compositional continuous c...     

Fabrication,microstructures, and properties of copper matrix composites reinforced by molybdenum-coated carbon nanotubes

Multiwalled carbon nanotubes(CNTs) were coated by a molybdenum layer using carbonyl thermal decomposition process with a precursor of molybdenum hexacarbonyl.The Mo-coated CNTs(Mo-CNTs) were added into copper powders to fabricate Mo-CNT/Cu composites by means of mechanical milling followed by spark plasma sintering.The Mo-CNTs were uniform dispersion in the Cu matrix when their contents were 2.5 vol.%-7.5 vol.%,while some Mo-CNT clusters were clearly observed at additions of 10.0 vol.%-15.0 vol.% Mo-CNTs in the mixture.The mechanical,electrical,and thermal properties of the Mo-CNT/Cu composites were characterized,and the results showed that the tensile strength and hardness were 2.0 and 2.2 times higher than those of CNT-free specimens,respectively.Moreover,the Mo-CNT/Cu composites exhibited an enhanced thermal conductivity but inferior electrical conductivity compared with sintered pure Cu.The uncoated CNT/Cu composites were fabricated by the similar processes,and the measured tensile strength,hardness,thermal conductivity,and electrical conductivity of the CNT/Cu composites were lower than those of the Mo-CNT/Cu composites.     

Microstructures and mechanical properties of Al 2519 matrix composites reinforced with Ti-coated SiC particles

Ti-coated SiC_p particles were developed by vacuum evaporation with Ti to improve the interfacial bonding of SiC_p/Al composites. Ti-coated SiC particles and uncoated SiC particles reinforced Al 2519 matrix composites were prepared by hot pressing, hot extrusion and heat treatment. The influence of Ti coating on microstructure and mechanical properties of the composites was analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the densely deposited Ti coating reacts with SiC particles to form TiC and Ti₅Si₃ phases at the interface. Ti-coated SiC particle reinforced composite exhibits uniformity and compactness compared to the composite reinforced with uncoated SiC particles. The microstructure, relative density and mechanical properties of the composite are significantly improved. When the volume fraction is 15%, the hardness, fracture strain and tensile strength of the SiC_p reinforced Al 2519 composite after Ti plating are optimized, which are HB 138.5, 4.02% and 455 MPa, respectively.     

Aging behavior of Al2O3 short fiber reinforced Al-Cu alloy composites

Al2O3 short fiber reinforced AI-Cu composites containing 1%, 3%, 5% and 7% Cu were fabricated by a squeeze casting technique. The as-cast Al2O3/Al-Cu composites were solution treated at 535 ℃ and then aged at 170, 190 and 210 ℃, respectively. Age hardening behavior of the Al2O3/Al-Cu composites was analyzed by measuring the hardness of the samples at different aging temperatures and aging time. Microstructures of the composites were observed by transmission electron microscope（TEM）. The results indicate that the hardness of the Al2O3/Al-Cu composites containing 7% Cu is much higher than that containing 1%-5% Cu because of the large amount of CuAl2 precipitant in the Al2O3/Al-Cu composite. With the increase of Cu content from 1% to 7%, the time needed for the appearance of peak hardness shortened, indicating that the addition of Cu can accelerate the kinetic of CuAl2 precipitation in the Al2O3/Al-Cu composites. The Al2O3/Al-Cu composite containing 7% Cu shows the highest increment of hardness by aging treatment. Therefore, in order to get a higher peak hardness, the Al2O3/Al-Cu composites need more Cu addition as compared with the un-reinforced Al-Cu alloys.     

SiC_f/Ti6Al4V/Cu复合材料的界面行为及力学性能

采用箔-纤维-箔法制备SiC_f/Ti6Al4V/Cu复合材料,研究Ti6Al4V在连续SiC纤维增强Cu基复合材料中作界面改性涂层时的界面反应结合特征.利用光学显微镜、扫描电镜和能谱仪分析复合材料显微组织、断口形貌以及SiC_f/Ti6Al4V界面和Ti6A14WCu界面的反应扩散特征.结果表明:该复合材料的抗拉强度并没有显著提高;SiC_f/Ti6Al4V界面反应非常微弱;而Ti6Al4V/Cu界面反应非常明显,主要是Ti原子与Cu原子之间的反应,反应层厚度约为20 μm;反应产物主要呈4层分布,分别为CuTi_2、CuTi、Cu_4Ti_3和Cu_4Ti.     

电子束物理气相沉积Cu-Mo复合材料微结构与性能

本文采用电子束物理气相沉积（EB-PVD）制备了纳米钼颗粒弥散强化铜基复合材料（Mo体积含量为 2.5%-10.8%）,对其材料微观结构、钼含量和硬度、电阻率关系进行了研究。结果表明：Cu-Mo复合材料基体由柱状晶铜组成,Mo颗粒平均直径为2.4-8.1nm;随着钼含量增加,铜基体柱状晶宽度逐渐减小,第二相Mo颗粒平均直径逐渐增加,硬度、电阻率逐渐增加;EB-PVD制备的Cu-Mo复合材料主要强化机制为Orowan机制。     

等径角挤压制备超细晶CNTs/AZ31镁基复合材料研究

采用模角为90°的模具对退火处理后的AZ31镁基碳纳米管复合材料进行了等径角挤压实验.结果表明:AZ31镁基碳纳米管复合材料经过一道次的等通道角挤压后,复合材料中就有大量的超细晶粒出现.随着道次数增加,超细晶粒比例逐渐增多.四道次挤压后复合材料晶粒尺寸达到1～5μm,显微硬度得到显著提高.     

Fabrication and wear behavior of CNT/Al composites

Aluminum matrix composites reinforced with carbon nanotube were fabricated by a powder metallurgy method. The effects of carbon nanotube content on the relative density, the hardness, and the friction and wear behavior of the composites under dry sliding condition were investigated using the ball （pin）-on-block tester. By scanning electron microscopy （SEM）, the worn surfaces and worn chips were observed, and the wear mechanism of composites was analyzed and discussed. The results indicate that the addition to the aluminum matrix of 2.0%（mass fraction） carbon nanotube causes the increase in the Vickers hardness of about 80%. Within the range of carbon nanotubes content from 1.0% to 2.0%, both the friction coefficient and wear rate of composites decrease with the increase of carbon nanotube content. The delamination wear is the main wear mechanism for the composites.     

Effects of technological parameters on microstructures and properties of in situ TiC_p/Fe composites

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｉＣｉｓｗｉｄｅｌｙｕｓｅｄａｓｉｎｓｉｔｕｒｅｉｎｆｏｒｃｉｎｇｐａｒｔｉｃｌｅｉｎｍｅｔａｌｍａｔｒｉｘｃｏｍｐｏｓｉｔｅｓ[1～ 5] ,ｂｅｃａｕｓｅｉｔｈａｓｎｏｔｏｎｌｙｈｉｇｈｍｅｌｔｉｎｇ ｐｏｉｎｔ ,ｈａｒｄｎｅｓｓ,ｅｌａｓｔｉｃｍｏｄｕｌｕｓａｎｄｅｘｃｅｌｌｅｎｔｃｏｒｒｏｓｉｏｎｒｅｓｉｓｔａｎｃｅ,ｂｕｔａｌｓｏｍｏｒｅｎｅｇ ａｔｉｖｅｓｔａｎｄａｒｄＧｉｂｂｓｆｏｒｍａｔｉｏｎｆｒｅｅｅｎｅｒｇｙ .Ｉｎｒｅｃｅｎｔｓｔｕｄｉｅｓ[6～ 9] ,ｈｏｗｅ…     

原位生成TiB_2/Al-Si-Mg复合材料的组织与性能

结合LSM法和MCR法原位反应生成TiB2 粒子增强Al Si Mg复合材料。研究发现 :原位生成TiB2 粒子呈等轴状且尺寸 <1μm ,大都均匀分布在共晶组织中 ,与共晶Si交织在一起 ,在α(Al)中只有少量的TiB2 粒子 ;原位TiB2 粒子可明显强化Al Si Mg复合材料 ,且随着TiB2 粒子数量的增加 ,强化效果也随之提高 ,而且延伸率也略有升高 ,如 6 %TiB2 /ZL10 4复合材料室温拉伸强度可达 2 96MPa ,延伸率为 5 .5 %;热处理 (T6)可将共晶Si由原先的连续棒状变为孤立的颗粒状 ,大幅度提高材料抗拉强度 ,使 6 %TiB2 /ZL10 4复合材料室温拉伸强度达386MPa ,而材料仍属于韧性材料     

Effect of carbon content on microstructure of in-situ Al_2O_(3p)-TiC_p/Al composites

1　ＩＮＴＲＯＤＵＣＴＩＯＮＸＤｔｅｃｈｎｉｑｕｅｉｓａｐａｔｅｎｔｏｆＭａｒｔｉｎＭａｒｉｅｔｔａＣｏｒ ｐｏｒａｔｉｏｎ[1] .Ｃｏｍｐｏｓｉｔｅｓｆａｂｒｉｃａｔｅｄｂｙｔｈｉｓｔｅｃｈｎｉｑｕｅｐｏｓｓｅｓｓｍａｎｙａｄｖａｎｔａｇｅｓ :1)Ｔｈｅｓｙｎｔｈｅｓｉｚｅｄｒｅｉｎ ｆｏｒｃｅ ｐａｒｔｉｃｌｅｓａｒｅｆｉｎｅｉｎｓｉｚｅａｎｄｅｑｕｉａｘｅｄｉｎｓｈａｐｅ[2 ,3 ] ;2 )Ｔｈｅｉｎｔｅｒｆａｃｉａｌｃｏｍｐａｔｉｂｉｌｉｔｙｂｅｔｗｅｅｎｉｎ ｓｉｔｕｒｅｉｎｆｏｒｃｅｐａｒｔｉｃｌｅｓ…     

Effects of nano-SiCp content on microstructure and mechanical properties of SiCp/A356 composites assisted with ultrasonic treatment

nano-SiC_p/A356 composites with different nano-SiC_p contents were prepared by squeeze casting after ultrasonic treatment (UT). The effects of SiC_p content on the microstructure and mechanical properties of the nanocomposites were investigated. The results show that with the addition of nano-SiC_p, the microstructure of nanocomposites is obviously refined, the morphology of the α(Al) grains transforms from coarse dendrites to rosette crystals, and long acicular eutectic Si phases are shortened and rounded. The mechanical properties of 0.5%, 1% and 2% (mass fraction) SiC_p/A356 nanocomposites are improved continuously with the increase of nano-SiC_p content. Especially, when the SiC_p content is 2%, the tensile strength, yield strength and elongation are 259 MPa, 144 MPa and 5.3%, which are increased by 19%, 69% and 15%, respectively, compared with those of the matrix alloy. The improvement of strength is attributed to mechanisms of Hall-Petch strengthening and Orowan strengthening.     

Tailoring microstructure and mechanical properties of aluminum matrix composites reinforced with novel Al/CuFe multi-layered core-shell particles

Aluminum matrix composites (AMCs), reinforced with novel pre-synthesized Al/CuFe multi-layered core- shell particles, were fabricated by different consolidation techniques to investigate their effect on microstructure and mechanical properties. To synthesize multi-layered Al/CuFe core-shell particles, Cu and Fe layers were deposited on Al powder particles by galvanic replacement and electroless plating method, respectively. The core-shell powder and sintered compacts were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDX), pycnometer, microhardness and compression tests. The results revealed that a higher extent of interfacial reactions, due to the transformation of the deposited layer into intermetallic phases in spark plasma sintered composite, resulted in high relative density (99.26%), microhardness (165 HV_0.3) and strength (572 MPa). Further, the presence of un-transformed Cu in the shell structure of hot-pressed composite resulted in the highest fracture strain (20.4%). The obtained results provide stronger implications for tailoring the microstructure of AMCs through selecting appropriate sintering paths to control mechanical properties.