Preparation and Arc Breakdown Behavior of Nanocrystalline W-Cu Electrical Contact Materials

Nanostructured （NS） W-Cu composite powder was prepared by mechanical alloying （MA）, and nanostructured bulk of W-Cu contact material was fabricated by hot pressed sintering in an electrical vacuum furnace. The microstructure, electric conductivity, hardness, breakdown voltage and arcing time of NS W-Cu alloys were measured and compared to conventional W-Cu alloys prepared by powder metallurgy. The results show that microstructural refinement and uniformity can improve the breakdown behavior, the electric arc stability and the arc extinction ability of nanostructured W-Cu contacts materials. Also, the nanostructured W-Cu contact material shows the characteristic of spreading electric arcs, which is of benefit to electric arc erosion.

Electrical, Thermal, and Mechanical Properties of Cu/Ti3AlC2 Functional Gradient Materials Prepared by Low-temperature Spark Plasma Sintering

Cu/Ti3AlC2 composite and functional-gradient materials with excellent electrical conductivity and thermal conductivity as well as good flexural properties were prepared by low-temperature spark plasma sintering of Cu and Ti3AlC2 powder mixtures. The phase compositions of the materials were analyzed by X-ray diffraction, and their microstructure was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. Further, the electrical conductivity, thermal conductivity, and flexural properties of the materials were tested. Results show that, for the composite materials, the resistivity rises from 0.75 × 10^-7 Ω·m only to 1.32 × 10^-7 Ω·m and the thermal diffusivity reduces from 82.5 mm^2/s simply to 39.8 mm^2/s, while the flexural strength improves from 412.9 MPa to 471.3 MPa, as the content of Ti3AlC2 is increased from 5 wt%to 25 wt%. Additionally, the functional-gradient materials sintered without interface between the layers exhibit good designability, and their overall electrical conductivity, thermal conductivity, and flexural strength are all higher than those of the corresponding uniform composite material.

Electrical Breakdown Characteristic of Nanostructured W-Cu Contacts Materials

Nanostructured （ NS ）W-Cu composite powder was prepared by mechanical alloying （ MA ）, and nanostructared bulk of W-Cu contact material was fabricated by hot press sintering in an electrical vacuum furnace. The rnicrostructure, electric conductivity, hardness and break down voltage of NS W- Cu alloys were measured and compared to those of conventional W-Cu alloys prepared by powder metallurg＇y. The experimental results show that microstructural refinement and uniformity can improve the breakdown behavior and the electric arc stability of nanostructared W- Cu contacts materials. Also, the wanostructured W- Cu contact material shows the characteristic of spreading electric arcs, which is of benefit to electric arc erosion.

Arc erosion behavior of a nanocomposite W-Cu electrical contact material

The erosion behavior of a nanocomposite W-Cu material under arc breakdown was investigated. The arc erosion rates of the material were determined, and the eroded surfaces and arc erosion mechanisms were studied by scanning eleclion microscopy. It is concluded that the nanocomposite W-Cu electrical contact material shows a characteristic of spreading arcs. The arc breakdown of a commercially used W-Cu alloy was limited in a few areas, and its average arc erosion rate is twice as large as that of the former. Furthermore, it is also proved that the arc extinction ability and arc stability of the nanocomposite W-Cu material are excellent, and melting is the major failure modality in the make-and-break operation of arcs.

Electrical breakdown characteristic of a Ce-doped W-Cu contact material

W-Cu composite powder doped with Ce （1.5 wt.%） was prepared by mechanical alloying （MA）,and the W-Cu contact material was fabricated by hot pressing sintering in an electrical vacuum furnace.The microstructure,electric conductivity,hardness,and breakdown voltage of the Ce-doped W-Cu alloy were measured and compared with a conventional W-Cu alloy prepared by powder metallurgy.The results show that microstructural refinement and uniformity can improve the breakdown behavior and the electric arc stability of the Ce-doped W-Cu contact material.Also,the Ce-doped W-Cu contact material shows the characteristic of spreading electric arc,which is beneficial to electric arc erosion.

Fabrication of W/Cu and Mo/Cu FGM as Plasma-facing Materials

W/Cu Functionally Graded Materials (FGM) was designed not only for reducing the thermal stress caused by the mismatch of thermal expansion coefficients, but also for combining the features of W, Mo - high plasma-erosion resistance and the advantages of Cu - high heat conductivity and ductility. Four different fabrication processes for W/Cu or Mo/Cu, including hot-pressing, Cu infiltration of sintered porosity-graded W skeleton, spark plasma sintering and plasma spraying, were investigated and compared. It was foundthat the hot-pressing process is difficult to keep the designed composition gradient, while the other three processes are successful in making W/Cu or Mo/Cu FGM. Meanwhile, microstructures and composition gradients are analyzed with SEM and EDAX.

Oxidized film on C_p/Cu-Cd electrical contact material

Constituents of the oxidized surface film on diamond particles reinforced Cu-Cd alloy matrix composite （Cp/Cu-Cd） were investigated by XPS. The results show that Cu2O is the main constituent when the oxidized film is thin; CuO appears only after the film is rather thick. The originally formed oxidized film on the Cp/Cu-Cd is about 10nm in thickness and is mainly composed of Cu2O and Cu. After oxidized at 120℃ over 30h, CuO is detected in the film.

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。

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.

Electrochemical migration behavior of Ag-plated Cu-filled electrically conductive adhesives

The electrochemical migration (ECM) behavior of the electrically conductive adhesives (ECAs) filled with pure Ag powder or Ag-plated Cu composite powder with varied Ag:Cu ratios was investigated under the condition of applying constant voltage and distilled water environment.ECM resistance was determined from the current-time curves.The microstructure and composition of ECM dendrite products were analyzed by SEM/EDS and XRD.It was found that the ECM resistance of Ag-plated Cu composite powder-filled ECAs was evidently higher than that of pure Ag powder-filled ECAs.The Ag:Cu ratio of composite powder in ECAs had notable influence on ECM resistance,which was enhanced with the decrease of Ag:Cu ratios.The composition of dendrites formed between cathode and anode during ECM process was not uniform for Ag-plated Cu-filled ECAs.An ECM inhibiting mechanism of Ag-plated Cu composite powder was proposed according to analysis of the electrochemical impedance spectroscopy,Tafel plot and dendrite composition.

Smart-microstructures of composites for electrical contacts with frameless packing of Cr and W in copper

W_(45)Cu_(55),Cr_(65)Cu_(35),and Cr_(32)W_(14)Cu_(54)alloys were obtained in order to study the mechanism of“smart response”of the structure of these alloys when using them as arc-resistant circuit-breakers.These alloys differ from industrial ones with frameless packing of Cr and W phases in the copper matrix.The alloy production method is based on the infiltration of copper melt into a mixture of non-compacted Cr and W powders under vibration exposure(80 Hz).The research results show an increase in the arc resistance of contacts when changing from“frame”packing of W to“frameless,”as well as the decisive role of Cr in the processes of self-dispersion of arc-resistant phases and passivation of W and Cu.Based on the obtained results,conclusions are drawn about the advantage of frameless packing of arc-resistant phases in copper and the reasons for the“smart behavior”of the structure of Cr-containing contacts in response to functional loads in the presence of oxygen and an inert atmosphere.

不同稀土元素对W-Cu电触头材料性能的影响

利用粉末冶金熔渗技术制备出添加不同稀土的W-Cu-RE电触头材料。比较不同稀土对其组织和力学性能的影响,并通过扫描电镜分析电弧烧蚀后的微观组织形貌。结果表明,W-Cu合金中最适宜添加的稀土单质为La,它使粘结相Cu呈连续网络分布。W-Cu-RE电触头材料较传统的W-Cu合金抗电弧烧蚀性能有了明显提高,达到30%。主要原因是触头间产生的电弧由于稀土的加入更容易使金属Cu气化而带走大量热能,从而起到保护基体的作用。

熔渗-焊接法制备W/Cu功能梯度材料的研究

采用熔渗－焊接法经过梯度W骨架制备，渗Cu及热压焊接三个步骤制备出W／Cu功能梯度材料。并对W／Cu梯度过渡层的显微结构进行了观察．

热压法制备W/Cu功能梯度材料

对热压法制备W/Cu功能梯度材料的可行性进行了研究 ,并对其组织结构进行了观察 ,对其表观抗弯强度及抗热震性进行了测试 .结果表明在 1 80 0℃ ,1 8N/mm2 ,2h条件下可以制备Cu含量最高为 2 2 .5 5vol.%的W/Cu功能梯度材料 ,其密度可达理论密度的 94.6% .热压W/Cu功能梯度材料的成分分布与最初设计的成分分布有较大偏差 .

添加Y_2O_3对CuW触头材料性能的影响

采用熔渗法制备添加Y_2O_3的CuW合金,研究了添加Y_2O_3对CuW材料静态性能、真空电击穿性能及显微组织的影响.结果表明:Y_2O_3的添加量为0～0.4%(质量分数)时,随着添加量的增加,合金的硬度逐渐升高,而电导率变化不大;当添加量为0.4%～1.2%时,硬度和电导率则明显下降.添加Y_2O_3相提高了CuW合金的耐电压强度,降低了材料的截流值添加Y_2O_3的CuW合金阴极斑点较小,锕液的飞溅现象减少.

溶胶-喷雾干燥W-10Cu和W-20Cu复合粉末烧结与组织性能研究

采用超细复合粉末直接烧结和传统W骨架熔渗两种方法制备W-10Cu、W-20Cu合金。研究两种方法制备的合金的致密化、显微组织与导电性能,并重点研究了超细复合粉末短时间内烧结和在高温烧结时的致密化行为。结果表明,超细W-10Cu、W-20Cu复合粉末在1200～1420℃烧结,相对密度均达到了99.1%,致密化与合金中的晶粒度和W-Cu复合粉末中的Cu相成分密切相关。与传统熔渗方法相比,超细复合粉末制备的合金显微组织细小、均匀,而且两者导电性能接近。

第一壁材料W/Cu界面设计与制备研究现状

介绍了目前解决W/Cu连接界面缓解热应力的方法——添加适配层。在对不同适配层进行分析后,选出最佳W/Cu适配层,再对W/Cu适配层进行结构优化分析,得出选用W/Cu功能梯度材料作为适配层具有足够的结合强度,而且良好的导热性能能有效地缓解热应力。此外,重点阐述了目前成功的制备的W/Cu功能梯度材料用作W/Cu第一壁材料的适配层的常用方法。最后,对W/Cu功能梯度材料用作适配层解决W/Cu第一壁材料连接界面的问题做出了总结和展望。

机械合金化制备的纳米晶W-Cu电触头材料

采用真空高温热压熔渗烧结工艺制备出密度为 99 5 %的纳米晶W Cu电触头材料。其组织结构和晶粒大小采用SEM ,TEM和XRD观察。同时就纳米晶W Cu电触头材料的硬度、电导率、耐电压强度和抗电弧烧蚀性与传统粉末冶金工艺制备的进行了对比分析。结果表明 ,纳米晶W Cu电触头材料的硬度、抗电弧烧蚀性及耐电压稳定性远优于传统熔渗法的W Cu合金 ,而电导率两者相差不大。

细晶W-Cu材料的导电性能

以喷雾干燥-氢还原W-10%Cu(质量分数)、W-20%Cu、W-30%Cu细晶复合粉末为原料,制备工字型拉伸样,并对粉末成分、烧结温度、保温时间对电导率的影响进行研究。结果表明:3种合金中,在1420℃时W-10%Cu和W-20%Cu的相对密度较大,达99.1%;在1380℃时W-30%Cu出现明显的致密化,相对密度最大,达98.7%。1420℃烧结1.5h后材料电导率达到最大,W-10%Cu、W-20%Cu、W-30%Cu的导电率分别为19、25、30MS/m,分别超过GB/T8320—2003的21.8%、27.2%、23.6%。

Cu-W复合电沉积工艺研究

电接触材料要求具有很好的抗电弧烧蚀和抗熔焊性能,但纯铜很难达到该种要求。利用复合电沉积方法,在纯铜表面形成Cu-W复合镀层,使其满足电触头材料的使用性能。重点研究了镀液中W的质量浓度、电流密度、搅拌强度和温度工艺参数对Cu-W电接触材料复合镀层中W微粒沉积量的影响,并且通过正交试验确定了复合电沉积的最优工艺:W的质量浓度为35g/L、电流密度为4A/dm2、搅拌强度为600 r/min、温度为50℃。