The arc erosion under medium direct currents in the argon flow was tested on tungsten-copper（W-Cu） contacts which were processed by hot extrusion and heat treatment. The scanning electron microscopy（SEM） and trans...The arc erosion under medium direct currents in the argon flow was tested on tungsten-copper（W-Cu） contacts which were processed by hot extrusion and heat treatment. The scanning electron microscopy（SEM） and transmission electron microscopy（TEM） were used to study the microstructure of the W-Cu powders and compacts. The contact resistance, arcing energy, and arcing time were continuously measured by JF04C contact materials test system. Changes in tungsten-copper contact surface were observed by SEM. The test results showed that the arcing time and arcing energy all increase with current and voltage, but the changes of average contact resistance are more complicated. For a short arcing time, the average contact resistance decreases with increasing current due to the vaporization of Cu. However, for a longer arcing time, it slightly increases due to the formation of high resistant films, compound copper tungsten. The formation of compound copper tungsten was confirmed by the increased Rc kept in the range from 1.1 to 1.6 mΩ. The compound copper tungsten is first exposed with a tungsten and copper-rich surface, and then totally exposed due to evaporation of copper from the surface. At last a stabilized surface is created and the crystals decrease from 8 μm to 2 μm caused by the arc erosion.展开更多
The microscopic Bouligand-type architectures of fish scales demonstrate a notable efficiency in enhancing the damage tolerance of materials;nevertheless,it is challenging to reproduce in metals.Here bioinspired tungst...The microscopic Bouligand-type architectures of fish scales demonstrate a notable efficiency in enhancing the damage tolerance of materials;nevertheless,it is challenging to reproduce in metals.Here bioinspired tungsten-copper composites with different Bouligand-type architectures mimicking fish scales were fabricated by infiltrating a copper melt into woven contextures of tungsten fibers.These composites exhibit a synergetic enhancement in both strength and ductility at room temperature along with an improved resistance to high-temperature oxidization.The strengths were interpreted by adapting the classical laminate theory to incorporate the characteristics of Bouligand-type architectures.In particular,under load the tungsten fibers can reorient adaptively within the copper matrix by their straightening,stretching,interfacial sliding with the matrix,and the cooperative kinking deformation of fiber grids,representing a successful implementation of the optimizing mechanisms of the Bouligand-type architectures to enhance strength and toughness.This study may serve to promote the development of new high-performance tungsten-copper composites for applications,e.g.,as electrical contacts or heat sinks,and offer a viable approach for constructing bioinspired architectures in metallic materials.展开更多
After cumulative discharge of gas discharge tube(GDT),it is easy to form a short circuit pathway between the two electrodes,which increases the failure risk and causes severe influences on the protected object.To redu...After cumulative discharge of gas discharge tube(GDT),it is easy to form a short circuit pathway between the two electrodes,which increases the failure risk and causes severe influences on the protected object.To reduce the failure risk of GDT and improve cumulative discharge times before failure,this work aims to suppress the formation of two short-circuit pathways by optimizing the tube wall structure,the electrode materials and the electrode structure.A total of five improved GDT samples are designed by focusing on the insulation resistance change that occurs after the improvement;then,by combining these designs with the microscopic morphology changes inside the cavity and the differences in deposition composition,the reasons for the differences in the GDT failure risk are also analyzed.The experimental results show that compared with GDT of traditional structure and material,the method of adding grooves at both ends of the tube wall can effectively block the deposition pathway of the tube wall,and the cumulative discharge time before device failure is increased by 149%.On this basis,when the iron-nickel electrode is replaced with a tungsten-copper electrode,the difference in the electrode’s surface splash characteristics further extends the discharge time before failure by 183%.In addition,when compared with the traditional electrode structure,the method of adding an annular structure at the electrode edge to block the splashing pathway for the particles on the electrode surface shows no positive effect,and the cumulative discharge time before the failure of the two structures is reduced by 22.8%and 49.7%,respectively.Among these improved structures,the samples with grooves at both ends of the tube wall and tungsten-copper as their electrode material have the lowest failure risk.展开更多
A corrosion study of two types of tungsten-copper(W-Cu)alloys in 3.38 wt.%Na Cl solution with different pH at 25℃were investigated using potentiodynamic polarization and immersion test.It is crucial that the corrosio...A corrosion study of two types of tungsten-copper(W-Cu)alloys in 3.38 wt.%Na Cl solution with different pH at 25℃were investigated using potentiodynamic polarization and immersion test.It is crucial that the corrosion behavior and preferential attacked phases of the W-Cu alloys were found to alter with p H.The micro-galvanic effect of tungsten phase and copper binder played a significant role.It was also proved that the existence of aggressive chloride ions could accelerate the Cu binder dissolution in acidic and neutral solution,which induced tungsten phase detachment and increased the corrosion rate of the W-Cu alloys.While Cl-would accelerate the Cu binder dissolution of W-Cu alloys at high potential during polarization test in strong alkaline solution.展开更多
文摘The arc erosion under medium direct currents in the argon flow was tested on tungsten-copper（W-Cu） contacts which were processed by hot extrusion and heat treatment. The scanning electron microscopy（SEM） and transmission electron microscopy（TEM） were used to study the microstructure of the W-Cu powders and compacts. The contact resistance, arcing energy, and arcing time were continuously measured by JF04C contact materials test system. Changes in tungsten-copper contact surface were observed by SEM. The test results showed that the arcing time and arcing energy all increase with current and voltage, but the changes of average contact resistance are more complicated. For a short arcing time, the average contact resistance decreases with increasing current due to the vaporization of Cu. However, for a longer arcing time, it slightly increases due to the formation of high resistant films, compound copper tungsten. The formation of compound copper tungsten was confirmed by the increased Rc kept in the range from 1.1 to 1.6 mΩ. The compound copper tungsten is first exposed with a tungsten and copper-rich surface, and then totally exposed due to evaporation of copper from the surface. At last a stabilized surface is created and the crystals decrease from 8 μm to 2 μm caused by the arc erosion.
基金the financial support by the National Key R&D Program of China under grant number 2020YFA0710404the National Natural Science Foundation of China under grant number 51871216+5 种基金the KC Wong Education Foundation(GJTD-2020-09)the Liao Ning Revitalization Talents Programthe State Key Laboratory for Modification of Chemical Fibers and Polymer Materials at Donghua Universitythe Opening Project of Jiangsu Province Key Laboratory of High-End Structural Materials under grant number hsm1801the Youth Innovation Promotion Association CASsupport from the Multidisciplinary University Research Initiative to University of California Riverside,funded by the Air Force Office of Scientific Research(AFOSR-FA9550–15–1–0009)and subcontracted to the University of California Berkeley。
文摘The microscopic Bouligand-type architectures of fish scales demonstrate a notable efficiency in enhancing the damage tolerance of materials;nevertheless,it is challenging to reproduce in metals.Here bioinspired tungsten-copper composites with different Bouligand-type architectures mimicking fish scales were fabricated by infiltrating a copper melt into woven contextures of tungsten fibers.These composites exhibit a synergetic enhancement in both strength and ductility at room temperature along with an improved resistance to high-temperature oxidization.The strengths were interpreted by adapting the classical laminate theory to incorporate the characteristics of Bouligand-type architectures.In particular,under load the tungsten fibers can reorient adaptively within the copper matrix by their straightening,stretching,interfacial sliding with the matrix,and the cooperative kinking deformation of fiber grids,representing a successful implementation of the optimizing mechanisms of the Bouligand-type architectures to enhance strength and toughness.This study may serve to promote the development of new high-performance tungsten-copper composites for applications,e.g.,as electrical contacts or heat sinks,and offer a viable approach for constructing bioinspired architectures in metallic materials.
基金supported by National Natural Science Foundation of China(No.U1834204)。
文摘After cumulative discharge of gas discharge tube(GDT),it is easy to form a short circuit pathway between the two electrodes,which increases the failure risk and causes severe influences on the protected object.To reduce the failure risk of GDT and improve cumulative discharge times before failure,this work aims to suppress the formation of two short-circuit pathways by optimizing the tube wall structure,the electrode materials and the electrode structure.A total of five improved GDT samples are designed by focusing on the insulation resistance change that occurs after the improvement;then,by combining these designs with the microscopic morphology changes inside the cavity and the differences in deposition composition,the reasons for the differences in the GDT failure risk are also analyzed.The experimental results show that compared with GDT of traditional structure and material,the method of adding grooves at both ends of the tube wall can effectively block the deposition pathway of the tube wall,and the cumulative discharge time before device failure is increased by 149%.On this basis,when the iron-nickel electrode is replaced with a tungsten-copper electrode,the difference in the electrode’s surface splash characteristics further extends the discharge time before failure by 183%.In addition,when compared with the traditional electrode structure,the method of adding an annular structure at the electrode edge to block the splashing pathway for the particles on the electrode surface shows no positive effect,and the cumulative discharge time before the failure of the two structures is reduced by 22.8%and 49.7%,respectively.Among these improved structures,the samples with grooves at both ends of the tube wall and tungsten-copper as their electrode material have the lowest failure risk.
基金finically supported by the project from the Multi-Year Research Grant(MYRG)of University of Macao(No.MYRG2018-00217-FST)。
文摘A corrosion study of two types of tungsten-copper(W-Cu)alloys in 3.38 wt.%Na Cl solution with different pH at 25℃were investigated using potentiodynamic polarization and immersion test.It is crucial that the corrosion behavior and preferential attacked phases of the W-Cu alloys were found to alter with p H.The micro-galvanic effect of tungsten phase and copper binder played a significant role.It was also proved that the existence of aggressive chloride ions could accelerate the Cu binder dissolution in acidic and neutral solution,which induced tungsten phase detachment and increased the corrosion rate of the W-Cu alloys.While Cl-would accelerate the Cu binder dissolution of W-Cu alloys at high potential during polarization test in strong alkaline solution.
