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。

MICROSTRUCTURE OF ELECTRODEPOSITED Ni-W-P-SiC COMPOSITE COATINGS

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Effects of addition of rare earth on properties and structures of Ni-W-B-SiC composite coatings

The effects of rare earth (RE) on the composition, phase structures, surface morphologies and hardness of electrodeposited RE Ni W B SiC composite coatings were discussed. The results show that W and SiC contents in the coatings increase with the increase of RE in the bath. When RE is added in the coatings, the grains are refined and the trend of formation of amorphous coatings is increased. Moreover, the thermal stability of the RE Ni W B SiC composite coatings is enhanced. The hardness of the coatings is increased with the increase of heat treatment temperature, and it reaches the peak value when heated at 400 ℃. Besides, the hardness of the RE Ni W B SiC coatings is higher than that of the Ni W B SiC coatings.

PROPERTIES OF ELECTRODEPOSITED AMORPHOUS Ni-W-P-SiC COMPOSITE COATINGS

The Effects of heat treatment temperature on the hardness,wear resistance and structure of the amorphous Ni-W-P-SiC composite coatings have been investigated.The results show that Ni-W-P-SiC composite coatings are amorphous under 300℃, partially crystalline at 300-400℃,and crystalline when heat treatment temperature reaches 400℃,the crystals being fine Ni3P phase particles.The hardness,wear resistance and the crystallization temperature of the composite coatings increase when an additive is added into the bath.The hardness and wear resistance of the coatings increase with increasing heat treatment temperature,and they will reach their peak values when the heat treatment temperature reaches 400℃.Corrosion experiment indicates that the corrosion resistance of amorphous Ni-W-P-SiC composite coatings in various kinds of corrosive media except nitric acid is better than that of stainless steel 1Cr18Ni9Ti.Scanning electron microscopy observation shows that the additive has no effect on the surface appearance of the coatings,but the current density and the pH value have considerable effects on the surface appearance.

STUDY ON PROPERTIES OF PULSE ELECTRODEPOSITED RE-Ni-W-P-SiC COMPOSITE COATINGS

The effects of pulse frequency f and duty cycle r on the deposition rate, composition, morphology, and hardness of pulse electrodeposited RE （rare earth）-Ni-W-P-SiC composite coatings have been studied. The results indicate that pulse current can improve the deposition rate of RE-Ni-W-P-SiC composite coatings; W, P, and SiC contents in the coating decrease with the increase of pulse frequency and reach the lowest value at f = 33Hz, whereas the RE content in the composite coatings increases with the increase of pulse frequency. SiC content decreases with the increase of duty cycle, W content reaches the lowest value, and P content reaches the highest value at r = 0.4; pulse current and RE can lead to smaller size of the crystalline grains; however, the effects of different pulse frequency and duty cycle on the morphologies of RE-Ni-W-P-SiC composite coatings are not obvious. The hardness of RE-Ni-W-P-SiC composite coatings is the highest when the duty cycle is at 0.6 and 0.8 and pulse frequency is at 50Hz. At the same pulse frequency, the hardness of RE-Ni-W-P-SiC composite coatings at r= 0.8 is higher than that at r= 0.6.

Structure and characteristics of electrodeposited RE-Ni-W-P-B_4C-PTFE composite coatings

Hardness, friction and wear characteristics of electrodeposited RE Ni W P B 4C PTFE composite coatings were studied, and the reason for these fine characteristics was explained in respect of structure. The results show that 1) the structure of RE Ni W P B 4C PTFE composite coatings experiences a transformation process from amorphous to mixture then to crystal as the heat treatment temperature rises; 2) incorporating of B 4C greatly increases the hardness of the coating; 3) the wear resistance of the coating is best with heat treatment for 1?h at 300?℃, which is greatly superior to that of the other traditional coatings.

Microstructure of Cu-based Amorphous Composite Coatings on AZ91D Magnesium Alloy by Laser Cladding

To improve the sliding wear resistance of AZ91D magnesium alloy, Cu-based amorphous composite coatings made of CuaTTi34Zr11Nis and Cu47Ti34Zr11Ni8＋20 wt pct SiC powders were fabricated on AZ91D magnesium alloy by laser cladding, respectively. SEM （scanning electron microscopy）, EDS （energy dispersive X-ray spectroscopy）, XRD （X-ray diffraction） and TEM （transmission electron microscopy） techniques were employed to study the phases of the coatings. The results show that the coatings mainly consist of amorphous phase and different intermetallic compounds. The reason of formation of amorphous phase and the function of SiC particles were explained in details.

Effect of Fe content on microstructure and mechanical properties of Cu-Fe-based composite coatings by laser induction hybrid rapid cladding

To select the proper composition and obtain an overall material?microstructure?property relationship for Cu?Fe alloy, theeffect of Fe content on microstructure and properties of Cu?Fe-based composite coatings by laser induction hybrid rapid claddingwas investigated. Microstructure characterization of the composite coatings was tested utilizing SEM, XRD and EDS. Microhardnessmeasurement was executed to evaluate the mechanical properties of the composite coatings. The results show that for low Fe content,the composite coating presents a feature that Fe-rich equiaxed dendrites are embedded in the Cu-rich matrix. With increasing Fecontent, the Fe-rich particles are dispersed in the Cu-rich matrix. With further increasing Fe content, large amounts of Cu-richparticles are homogeneously dispersed in the interdendrite of the Fe-rich matrix. Correspondingly, the average microhardness of thecomposite coatings increases gradually with the increase of Fe content and the microhardness of Cu14.5Fe83Si2C0.5 coating is muchtwice higher than that of the substrate.

纳米W-Cu复合粉体制备的研究进展

W-Cu复合材料结合了W、Cu金属各自优良性能,具有良好的高温强度、延展性、抗电弧烧结性、耐高温氧化和低膨胀系数等特点,广泛应用于机械加工、国防工业、航空航天、电子信息、军事等领域。以超细纳米W-Cu复合粉体为原材料是制备出性能优越的W-Cu复合材料的主要途径之一,受到国内外学者的广泛关注。主要总结了W-Cu超细纳米复合粉体的制备方法,如机械合金化法、化学共沉淀法、水热合成-共还原法、喷雾干燥法、溶胶-凝胶法、冷冻-干燥法、燃烧法等,并通过分析现阶段制备W-Cu纳米复合粉体存在的问题,提出了未来该领域的研究方向。

HfO_(2)掺杂对湿化学法制备W-20Cu复合材料微观组织和性能的影响

采用湿化学法制备W-20Cu复合粉体,通过喷雾干燥法得到球壳状前驱体,再通过氢气还原成功将弥散分布的HfO_(2)第二相颗粒引入W-20Cu复合粉体,确定了引入的HfO_(2)在W-20Cu复合粉体中的存在形式以及分布状态。采用高温液相烧结制备了细小HfO_(2)颗粒均匀分布的W-20Cu复合材料。结果表明:由于HfO_(2)颗粒在W颗粒表面和W/Cu界面间隙中弥散分布,抑制了W颗粒在烧结过程中的粗化,从而降低了W-W的连通性,使得W-20Cu复合材料表现出较高的综合性能。其中,烧结温度在1350℃时,块体的致密度较高,均为97%,掺杂0.5%HfO_(2)制备得到的复合材料综合性能最佳,其硬度最大可达到338HV,抗弯强度为826 MPa,热导率为209 W/(m·K)。

Microstructure and Thermal Properties of SiCp/Cu Composites with Mo Coating on SiC Particles

SiCp/Cu composites with a compact microstructure were successfully fabricated by vacuum hot-pressing method. In order to suppress the detrimental interfacial reactions and ameliorate the interfacial bonding between copper and silicon carbide, molybdenum coating was deposited on the surface of silicon carbide by magnetron sputtering method and crystallized heat-treatment. The effects of the interfacial design on the thermo-physical properties of Si Cp/Cu composites were studied in detail. Thermal conductivity and expansion test results showed that silicon carbide particles coated with uniform and compact molybdenum coating have improved the comprehensive thermal properties of the Si Cp/Cu composites. Furthermore, the adhesion of the interface between silicon carbide and copper was significantly strengthened after molybdenum coating. Si Cp/Cu composites with a maximum thermal conductivity of 274.056 W/（m·K） and a coefficient of thermal expansion of 9 ppm/K were successfully prepared when the volume of silicon carbide was about 50%, and these Si Cp/Cu composites have potential applications for the electronic packageing of the high integration electronic devices.

W-Cu复合材料的应用现状及掺杂改性的研究进展

W-Cu复合材料因具有高的硬度、耐磨性、抗烧蚀性能、导电性和导热性以及低热膨胀系数等综合性能而被广泛应用于多种工业领域。本文介绍了W-Cu复合材料的最新研究进展及其在电触头、微电子、军事、功能梯度材料方面的应用现状,着重总结和分析了目前W-Cu复合材料掺杂改性的分类及原理,以及掺杂改性对材料性能的影响,最后提出了W-Cu复合材料未来发展的潜在问题和值得关注的研究方向。

等离子体技术制备具有亚微米颗粒结构的球化W-Cu伪合金微粉

采用复杂多级方法研究并证实制备具有亚微米/纳米级内部结构的球形W-Cu复合微粉的可能性。首先,采用等离子体化学合成法制备具有核壳结构的W-Cu纳米粉末(W核及Cu壳)。然后,将W-Cu纳米粉末与蔗糖的水悬浮液进行喷雾干燥,形成25~63μm的微粒,收率为50%。最后,用热等离子体射流处理由纳米粉末组成的微粒,形成致密的球形W-Cu颗粒。成品粉末的球化度为90%~95%,体积密度为8.1 g/cm^(3),流动性约为12 s/50 g,杂质中O、C和H的含量(质量分数)分别为0.7%、0.02%~0.2%和0.03%~0.05%。

组合靶共溅射沉积Cu-W复合薄膜的结构与性能

用嵌入组合型靶材,采用磁控共溅射方法,在单晶硅和聚酰亚胺衬底上制备Cu-W复合薄膜。分别运用能谱仪、X射线衍射仪、扫描电镜和原子力显微镜对Cu-W复合薄膜的成份、结构及表面形貌进行分析表征。选用微小力测试系统、纳米压痕仪及四探针仪分别测试复合薄膜的屈服强度σ_(0.2)和裂纹萌生临界应变ε_(c)、显微硬度H及电阻率ρ。结果表明:可通过调整组合型靶材环状溅射刻蚀区内W靶所占的面积比,有效地调控复合薄膜的W含量。随W靶的面积占比从6%增至30%,Cu-W复合薄膜的W含量从2.6 at.%增至16.9 at.%。W在Cu中的固溶度延展,复合膜内存在面心立方(fcc)Cu(W)亚稳固溶体,随复合膜中W含量增加,W在Cu中的固溶度从1.7 at.%W增至10 at.%W,复合膜的平均晶粒从32 nm减小至16 nm,表面光洁度提高。W含量增加时,复合膜的屈服强度σ_(0.2)、显微硬度H及电阻率ρ增加,而裂纹萌生临界应变ε_(c)减小。

钛合金脉冲电沉积Cu-WC复合镀层的硬度与摩擦磨损性能

为有效提高钛合金的抗摩擦磨损性能,在钛合金表面脉冲电沉积Cu-WC复合镀层。分别研究了平均电流密度、脉冲占空比对复合镀层的微观形貌、WC颗粒含量、硬度以及摩擦磨损性能的影响。结果表明:当平均电流密度为1.5 A/dm^(2)、脉冲占空比为20%时,电沉积的Cu-WC复合镀层致密性最好,WC颗粒含量接近2.4%,其硬度(240.4 HV)约为纯Cu镀层的2倍,还表现出良好的抗摩擦磨损性能,平均摩擦系数较钛合金降低约38%。适当增大平均电流密度(0.5~1.5 A/dm^(2))或提高脉冲占空比(10~20%)能使较多WC颗粒参与电沉积过程,起到明显细化晶粒作用和弥散强化作用,促进形成结构致密的Cu-WC复合镀层,因而具有较高硬度和良好的抗摩擦磨损性能。

磁控共溅射W-Cu复合薄膜的工艺优化及性能研究

采用磁控共溅射沉积工艺,结合正交试验方法制备W-Cu复合薄膜。用扫描电子显微镜(SEM)观察W-Cu复合薄膜表面形貌,能谱仪(EDS)分析复合薄膜成分。微小力测试系统、纳米压痕仪及四探针仪分别测试复合薄膜的屈服强度σ_(0.2)、裂纹萌生临界应变ε_(c)、显微硬度H及电阻率ρ。结果表明,靶功率密度PD、溅射气压P及靶基距D_(TS)这三个工艺参数影响W-Cu复合薄膜的成分、沉积率、微观结构及力学和电学性能。优化的工艺参数为:PD=10 W/cm^(2)、P=2 Pa、D_(TS)=150 mm。该工艺条件下制备的W-Cu复合薄膜中Cu含量为42.2%(原子分数),沉积率6.6 nm/min。其性能为σ_(0.2)=0.86 GPa,ε_(c)=0.62%,H=7.35 GPa,ρ=19.6μΩ·cm。该复合膜微观结构呈均质化特征,W和Cu组元分布均匀。

Preparation of nanosized W/Cu composite powder by sol-gel technique

Cu(NO3)(2) and (NH4)(6)H(2)W(12)O(40)center dot 4H(2)O were used to prepare W/Cu nanosized composite powder by sol-gel technique. The influences of heat treatment process, pH value of the solution and the amount of an addition agent on particle size were investigated by DSC, XRD and TEM. The results show that, at a certain heat treatment temperature, the W/Cu nanoparticle size increases with the pH value or the amount of the addition agent increasing.

Corrosion resistance of electrodeposited RE-Ni-W-P-SiC composite coating

Immersion experiment results show that corrosion rate of the as deposited RE Ni W P SiC composite coating in HCl solutions increases with the rise of HCl concentration. On the contrary, the corrosion rate of the composite coating after heat treatment decreases with increasing HCl concentration. The corrosion rates of the composite coatings in as deposited state and after heat treatment in H 2SO 4 and H 3PO 4 solutions respectively decrease with the rise of H 2SO 4 and H 3PO 4 concentrations. The corrosion rate of the composite coating as deposited in FeCl 3 solutions decreases with increasing FeCl 3 concentration, while the rate of the composite coating after heat treatment increases with the rise of FeCl 3 concentration. The corrosion rate of 316L stainless steel in the corrosion media of H 2SO 4, HCl, H 3PO 4 and FeCl 3 solutions at different concentrations increases with rising concentration. In addition, the corrosion rate of 316L stainless steel in the corrosion media of H 2SO 4, HCl, H 3PO 4 and FeCl 3 solutions respectively is much greater than that of the RE Ni W P SiC composite coating as deposited and after heat treatment in the same corrosion media. [

Microstructure of electrodeposited RE-Ni-W-P-SiC composite coating

The components and microstructure of the RE Ni W P SiC composite coating were analyzed by means of EPXDS, SEM and XRD. The results showed that the composite coating containing 5%～14%RE, 4%～7%SiC, 12%～15%P and 5%～6%W was obtained by use of appropriate bath composition and plating conditions. The as deposited composite coating is amorphous and it becomes mixture when the temperature is raised from 200 ℃ to 400 ℃. However, the composite coating is crystal when the temperature is over 400 ℃. Scanning electron microscopy indicates that the heat treatment temperature has no effect on the surface morphologies of the RE Ni W P SiC composite coating. This is to say that the composite coating has a better heat stability of microstructure and high temperature oxidation.

CATHODIC PROCESS AND WEAR RESISTANCE OF ELECTRO-DEPOSITED RE-Ni-W-P-SiC COMPOSITE COATING

Cathodic deposition current density of the composite coatings increases when SiC par-ticles and rare earth (RE) were added in the bath, which is profitable for Ni- W-P alloy to deposit in the cathod, forming Ni-W-P-SiC and RE-Ni-W-P-SiC composite coatings. On the contrary, the addition of PTFE in the bath decreases cathodic deposition current density of the coatings. The current density increases a little when the amount of RE is 7-9g/l; however, the current density increases greatly when the amount of RE is increased to 11-13g/l. Bui ij the amount of RE is raised further, the current density decreases. Hardness and wear resistance of RE-Ni-W-P-SiC composite coating have been studied, and the results show that the hardness and wear resistance of RE-Ni-W-P-SiC composite coating increase with increasing heat treatment tempera-ture, which reach peak values at 400℃; while the hardness and wear resistance of the coating decrease with the rise of heat treated temperature continuously.