Microstructure and properties of Cu matrix composites reinforced with surface-modified Kovar particles

The thermal conductivity of Cu/Kovar composites was improved by suppressing element diffusion at the interfaces through the formation of FeWO_(4)coating on the Kovar particles via vacuum deposition.Cu matrix composites reinforced with unmodified(Cu/Kovar)and modified Kovar(Cu/Kovar@)particles were prepared by hot pressing.The results demonstrate that the interfaces of Cu/FeWO_(4)and FeWO_(4)/Kovar in the Cu/Kovar@composites exhibit strong bonding,and no secondary phase is generated.The presence of FeWO_(4)impedes interfacial diffusion within the composite,resulting in an increase in grain size and a decrease in dislocation density.After surface modification of the Kovar particle,the thermal conductivity of Cu/Kovar@composite is increased by 110%from 40.6 to 85.6 W·m^(-1)·K^(-1).Moreover,the thermal expansion coefficient of the Cu/Kovar@composite is 9.8×10^(-6)K^(-1),meeting the electronic packaging requirements.

WEAR TRANSITIONS OF C/Cu COMPOSITE MATERIALS

An unlubricated sliding friction test on C/Cu composite materials is described. The result of the test proves that adhesive wear is the domination. At a certain speed, when the load upon the test block is light, the wear rate remains low level and the friction pair has a good antifriction performance. But when the load increases to a certain value, the wear transitions happen, the wear becomes severe.

Microstructure and property of sub-micro WC-10 %Co particulate reinforced Cu matrix composites prepared by selective laser sintering

The WC-10%Co particulate reinforced Cu matrix composite material with a WC-Co∶Cu mass ratio of 20∶80 was successfully fabricated by selective laser sintering(SLS) process. The following optimal processing parameters were used: laser power of 700 W, scan speed of 0.06 m/s, scan line spacing of 0.15 mm, and powder layer thickness of 0.3 mm. The microstructure, composition, and phase of the laser processed material were investigated by scanning electron microscopy(SEM), X-ray diffraction(XRD), and energy dispersive X-ray(EDX) spectroscopy. The results show that the bonding mechanism of this process is liquid phase sintering. The Cu and Co act as the binder phase, while the WC acts as the reinforcing phase. The non-equilibrium effects induced by laser melting, such as high degrees of undercooling and high solidification rate, result in the formation of a metastable phase CoC0.25. The WC reinforcing particulates typically have three kinds of morphology. They are agglomerated and undissolved, incompletely separated and partially dissolved, separated and dissolved, which indicates that particle rearrangement acts as the dominant sintering mechanism for the larger WC, while dissolution-precipitation prevails for the smaller WC particles. Microhardness tester was used to determine the Vickers hardness across the cross-section of the laser sintered sample, with the average value being HV0.1268.5. However, the hardness varied considerably, which might be attributed to the WC segregation and the high solidification rate experienced by the molten pool.

Influence of additives and concentration of WC nanoparticles on properties of WC−Cu composite prepared by electroplating

The effects of additives(polyethylene glycol(PEG),sodium dodecyl sulfate(SDS))and WC nano-powder on the microstructure,relative density,hardness and electrical conductivity of electroplated WC−Cu composite were investigated.The preparation mechanism was also studied.The microstructure of samples was analyzed by XRD,SEM,EDS,TEM and HRTEM.The synergistic effect of PEG and SDS made the WC−Cu composite more compact during the electroplating process.The hardness of WC−Cu composites increased with the increase in WC content,while the electrical conductivity decreased with the increase in WC content.The density of samples tended to increase initially and then decreased with increase in the additive content.When the electroplating solution contained 10 g/L WC nanopowder,0.2 g/L PEG and 0.1 g/L SDS,the WC−Cu composite exhibited hardness of HV 221 and electric conductivity of 53.7 MS/m.Therefore,the results suggest that WC−Cu composite with excellent properties can be obtained by optimizing the content of additives and WC particles.

Preparation and electrochemical property of Cs0.35V2O5/Cu composite material

Cs0.35V2O5 was successfully synthesized as cathode material for lithium secondary battery by the rheological phase reaction method from Cs2CO3 and NH4VO3. The Cs0.35V2O5/Cu composite material was prepared by the displacement reaction in CuSO4 solution using zinc powder as a reductant. The structure and electrochemical property of the so-prepared powders were characterized by means of XRD （powder X-ray diffraction） and the galvanostatic discharge-charge techniques. The results show that the electrochemical property of Cs0.35V2O5/Cu composite material is significantly improved compared to the bulk Cs0.35V2O5 material. The Cs0.35V2O5/Cu composite material exhibits the first discharge capacity as high as 164.3 mAh.g -1 in the range of 4.2-1.8V at a current rate of 10 mA.g-1 and remains at a stable discharge capacity of about 110 mAh.g-1 within 40 cycles.

三维互穿结构Cu-W触头抗熔焊机理

触头闭合回跳电弧引起的开关电器动熔焊问题,直接影响大功率接触器的电寿命和可靠性。为此设计了2种三维互穿有序结构的四边形和菱形十二面体的Cu-W复合材料触头,围绕触头动熔焊过程中的电弧、熔池、液滴溅射及凝固相变降温等问题,建立触头熔池流体动力学模型和冷凝降温数学模型,研究了2种有序结构和商用无序结构的触头阳极在闭合回跳电弧作用下熔化温度分布、熔池喷溅形貌和接触区域金属凝固过程,通过模拟熔焊实验平台进行了熔焊力验证。结果表明,通过调节三维互穿有序W骨架结构,能够有效抑制熔池扩散和液态金属喷溅,并降低熔焊力,从而提高Cu-W复合材料的抗熔焊性能。

Effects of rolling and annealing on microstructures and properties of Cu/Invar electronic packaging composites prepared by powder metallurgy

The Cu/Invar composites of 40% Cu were prepared by powder metallurgy, and the composites were rolled with 70% reduction and subsequently annealed at 750 ℃. Phases, microstructures and properties of the composites were then studied. After that, the amount of a-Fe（Ni,Co） in the composites is reduced, because a-Fe（Ni,Co） partly transfers into y-Fe（Ni,Co） through the diffusion of the Ni atoms into a-Fe（Ni,Co） from Cu. When the rolling reduction is less than 40%, the deformation of Cu takes place, resulting in the movement of the Invar particles and the seaming of the pores. When the rolling reduction is in the range from 40% to 60%, the deformations of Invar and Cu occur simultaneously to form a streamline structure. After rolling till 70% and subsequent annealing, the Cu/Invar composites have fine comprehensive properties with a relative density of 98.6%, a tensile strength of 360 MPa, an elongation rate of 50%, a thermal conductivity of 25.42 W/（m.K） （as-tested） and a CTE of 10.79× 10-6/K （20-100 ℃）.

Improvement of the matrix and the interface quality of a Cu/Al composite by the MARB process

The matrix accumulative roll bonding technology （MARB） can improve the matrix performance of metal composite and strengthen the bonding quality of the interface./n this research, for the fwst time, the technology of MARB was proposed. A sound Cu/AI bonding composite was obtained using the MARB process and the bonding characteristic of the interface was studied using scanning electricity microscope （SEM） and energy-dispersive spectroscopy （EDS）. The result indicated that accumulation cycles and diffusion annealing temperature were the most important factors for fabricating a Cu/AI composite material. The substrate aluminum was strengthened by MARB, and a high quality Cu/AI composite with sound interface was obtained as well.

A Novel Technique for Preparation of Electrically Conductive ABS/Cu Polymeric Gradient Composites

A novel technique for preparing functionally gradient electrically conductive polymeric composites was developed by using of solution casting technique on the principle of Stokes＇ law. Acrylonitrile- butadiene-styrene/Cu （ABS/Cu） gradient polymeric composites were prepared successfully using this technique. The gradient structures, electrically conductive performance and mechanical properties of the ABS/Cu composites were investigated. Optical microscope observation shows that the gradient distribution of Cu particles in ABS matrix was formed along their thickness-direction. The electrically conductive testing results indicate that the order of magnitude of surface resistivity was kept in 10^15 Ω at ABS rich side, while that declined to 10^5 Ω at Cu particles rich side, and the percolation threshold was in the range of 2.82 vo1%- 4.74 vol% Cu content at Cu particles rich side. Mechanical test shows that the tensile strength reduced insignificantly as the content of Cu increases owing to the gradient distribution.

表面改性WC颗粒增强铜基复合材料的微观结构与摩擦学特性

WC与Cu界面结合强度不足严重影响铜基复合材料的摩擦磨损性能,但业内尚未有良好的界面调控措施以优化性能。采用铜表面改性WC颗粒改善WC与Cu基体界面,经粉末冶金工艺制备Cu改性WC颗粒增强铜基复合材料,开展复合材料的微结构表征与摩擦学性能研究。研究表明,Cu改性WC颗粒可良好地嵌入铜基体,颗粒与Cu基体界面较基体弹性恢复能力提升33%,硬度提升20%。15 wt.%Cu改性WC增强铜基复合材料具有最佳的物理性能与摩擦学特性,较纯铜粉末冶金材料体积密度提升8%,布氏硬度提升15%,摩擦因数波动幅度最小并稳定在0.75,磨损量最小为0.075 mm^(3),磨痕轮廓圆滑,磨损面最完整且大面积成膜。随Cu改性WC含量增大,主要磨损机制由黏着磨损转变为剥离磨损,Cu改性WC颗粒促进摩擦转移层的形成,抑制磨损面裂纹的横向扩展。Cu改性WC颗粒与铜基体界面结合强度显著提升,15 wt.%复合材料抑制黏着磨损与疲劳磨损,摩擦学性能优异。采用Cu改性WC颗粒增强铜基摩擦材料有望成为优化WC与Cu基体界面提升铜基复合材料摩擦学性能的重要备选途径。

PTFE/Cu材料动态压缩特性

通过冷等静压和冷压烧结制备出六种不同密度的聚四氟乙烯(polytetrafluoroethylene,PTFE)/Cu复合材料,并采用霍普金森系统研究了密度和制备方法对PTFE/Cu动态力学性能影响。结果表明,冷压烧结试样在其烧结过程中发生纵向膨胀,导致密度降低,且试样表面生成一层金属膜;冷压烧结试样的动态压缩性能优于冷等静压试样;冷压烧结后的PTFE/Cu材料中PTFE晶体发育更好,对Cu颗粒包裹力更大,界面结合力更高,提升了冷压烧结PTFE/Cu材料的力学性能。

Synthesis and Characterizations of Nanocrystalline WC-Co Composite Powders by a Unique Ball Milling Process

In order to explore the high efficiency of fabricating nanocrystalline WC-Co composite powders, this paper presented a unique high energy ball milling process with variable rotation rate and repeatious circulation, by which nanocrystalline WC-10Co-0.8VC-0.2Cr3C2 (wt pct) composite powders with mean grain size of 25 nm were prepared in 32 min, and the quantity of the powders for a batch was as much as 800 grams. The as-prepared powders were analyzed and characterized by chemical analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential thermal analysis (DTA). The results show that high energy ball milling with variable rotation rates and repeatious circulation could be used to produce nanocrystalline WC-Co powder composites with high efficiency. The compositions of the powders meet its specifications with low impurity content. The mean grain size decreases, lattice distortion and system energy increase with increasing the milling time. The morphology of nanocrystalline WC-Co particles displays dominantiy sphere shape and their particle sizes are all lower than 80 nm. The eutectic temperature of the nanocrystalline WC-10Co-0.8VC-0.2Cr3C2 composites is about 1280℃.

Atom Diffusion Behavior and Bonding Strength of Ag/Cu Composite Interface

The atom (Ag,Cu) diffusion behavior and the effect of technology on the interface of rolled Ag/Cu composite contact were investigated. The concentration of Ag and Cu atoms near the interface was determined with electron probe. The bonding strength of composite interface was tested and the fracture in tensile sample was observed by SEM. The results show that there was inter diffusion of Ag and Cu atoms on the interface, which formed compact layer with high bonding strength of 98 MPa. The practical application proved that the Ag/Cu composite interface is reliable.

Influence of Microstructure Refinement on Strain Strengthening Effect of Cu-Ag Alloy in situ Filamentary Composites

The Cu-10Ag and Cu-10Ag-RE （RE=Ce, Y） alloys in situ filamentary composites were prepared. The relationships of the ultimate tensile strengths （UTS） and microstructure changes of the composites were studied. With increasing of the true strain η, the sizes of the Ag filaments in the composites reduce according to a negative exponential function of η:d=d0·exp（-0.228η）, and the UTS of the composites increase also according to a exponential function of η, σ Cu/Ag=σ 0（Cu）+[k Cu/Agd0 -1/2]exp（η/3）, here d0 is a coefficient related to the original size of Ag phase. The strain strengthening follows a two-stage strengthening effect. The strengthening mechanisms are related to changes of microstructure in the deformation process. At the low true strain stage, the strengthening is mainly caused by the working hardening controlled by dislocation increasing; at the high true strain stage, the strengthening is mainly caused by the super-fine Ag filaments and the large coherent interfaces between the Ag filaments and Cu matrix. The trace RE additions and the rapid solidification obviously refine scales of the Ag filament of the composites, and therefore obviously increased the strain strengthening rate. The microstructure refinement of the composites, especially the refinement of Ag filament, is the main reason of the high strain strengthening effect in Cu-Ag alloy in situ filamentary composites.

CuS/GO复合材料的构筑及对罗丹明B的高光催化活性

光催化降解是一种有效降解罗丹明B的方法,为环境保护和人类健康做出了巨大的贡献,因此其具有广泛的应用前景.采用改良的Hummers法制备氧化石墨烯(GO),在此基础上,采用水热合成法制得硫化铜/氧化石墨烯(CuS/GO)纳米复合材料.通过傅里叶红外(FITR)、X-射线衍射仪(XRD)、透射电子显微镜(TEM)、X-射线光电子能谱仪(XPS)等对复合材料进行表征.结果表明,随着醋酸铜含量的增加,负载在GO的CuS纳米粒子的量也随之增加,同时粒子尺寸也发生了变化.当醋酸铜含量占35.9%时,复合材料中CuS纳米粒子为3 nm,其形貌良好,负载均匀,且CuS的尺寸较小.CuS/GO复合材料对罗丹明B表现出了良好的光催化活性.

WC/Cu复合材料组织及烧结过程研究

研究了粉末冶金冷压—烧结法制备的WC/Cu复合材料在不同温度和时间烧结时的组织变化及WC含量对烧结过程的影响 ,分析了该材料的烧结过程。结果表明 ,WC颗粒推迟了烧结进程。烧结过程中烧结体无明显收缩 ,WC颗粒显著阻碍了晶粒长大。WC/Cu复合材料的烧结过程可分为粘结、烧结颈长大、闭孔球化。

WC/Cu复合材料制备及其高温性能

用机械合金化法结合冷变形 ,制备了WC/Cu复合材料 ,研究了冷变形后复合材料的组织特征和高温退火时的性能变化。结果表明 :烧结后的材料经冷变形 ,组织呈显著纤维状 ,WC颗粒弥散分布 ,密度明显提高 ,达到理论密度的 99 2 % ;复合材料经 6 0 0～ 90 0℃高温退火 ,强度和硬度略有下降 ,塑性则有大幅提高 ;90 0℃退火时未发生明显的再结晶 ,界面结合良好 ;

WC/Cu大电流滑动电接触材料的研究

为了提高电接触材料的导电、导热等性能,笔者采用粉末冶金溶渗技术制备出WC/Cu滑动电接触材料,并对其显微组织和性能进行了系统研究。结果表明:WC60～90/Cu滑动电接触材料随着WC含量的增加,材料的密度由11.508 g/cm3增加到13.305 g/cm3,硬度由HB187增加到HB477,导电率由14.6 m/(Ω.mm2)下降到10.6 m/(Ω.mm2)。耐磨性随着WC含量的增加显著提高,但高Cu含量的孕育期较长。磨损机制以磨粒磨损和表面接触疲劳为主。建议使用含量为WC70/Cu30～WC80/Cu20的滑动电接触材料。

高能球磨制备纳米级WC/Cu复合粉末的研究

利用XRD、SEM等分析研究了高能球磨时间对WC/Cu复合粉末结构、形貌及相的影响。结果表明 ,随球磨时间的延长复合粉末发生细化达到纳米级粒度 ,球磨 2 4h可获得稳定晶粒尺寸 ,最小晶粒尺寸为 2 1 5nm。其中WC粉末晶粒细化速率较Cu的慢 ;球磨过程中 ,有少量的WC固溶于Cu中 ,形成Cu(WC)

Al_2O_3/Cu-WC复合材料热变形行为及热加工图

在Gleeble 1500D热模拟机上对Al2O3/Cu-WC复合材料进行热压缩实验,研究变形温度为350-750℃、应变速率为0.01-5 s 1条件下的热变形行为。结果表明:Al2O3/Cu-WC复合材料高温流变应力—应变曲线主要以动态再结晶软化机制为特征,峰值应力随变形温度的降低或应变速率的升高而增加;热变形过程中的稳态流变应力可用双曲正弦本构关系式来描述,其激活能为229.17 kJ/mol。根据材料动态模型,计算并建立Al2O3/Cu-WC复合材料的热加工图,据此确定热变形流变失稳区及热变形过程的最佳工艺参数,其热加工温度为650-750℃,应变速率为0.1-1 s 1。