Shu Hua Liang

Study on the Interface Diffusion Bonding of the Copper Alloy/30CrMnSi Steel

The copper alloy/30CrMnSi steel bi-metal composite materials were prepared by the interface diffusion bonding method. The diffusion of elements close to the bonding interface was studied and the formation and growth mechanism of dissolution layer were discussed as well. The results showed that a diffusion transition layer could be formed with the different widths for copper alloy/30CrMnSi steel integrated material. A diffusion transition layer was formed close to 30CrMnSi steel side due to the inter-diffusion of the alloy elements. The microstructure characterization showed that no harmful brittle phase presented around the interface, and two heterogeneous materials had a good metallurgical bonding.

Wear Resistance of Cu10Al5Fe5Ni Alloy

The effect of ambient temperature, materials state and lubrication condition on wear resistance of Cu10Al5Fe5Ni alloy was investigated. The wear surface morphology was characterized by a scanning electron microscope (SEM), and the wear mechanism was discussed as well. The results show that the friction coefficient of Cu10Al5Fe5Ni alloy increases and then decreases with increasing temperature. The wear rate of the Cu10Al5Fe5Ni alloy after solid solution and ageing treatment is less than that of the as-cast alloy, and the wear rate of Cu10Al5Fe5Ni alloy reduces dramatically from 5.31×10-5 mm3 / (m· N) into 1.80×10-6 mm3 / (m·N) after adding lubricating oil. At elevated temperature, the prior wear mechanism is the fatigue wear, accompanying by slight abrasive wear and adhesive wear for the aged Cu10Al5Fe5Ni alloy.

Vacuum Arc Motion Characteristics on CuWCr Composites

The CuWCr composites were respectively fabricated by the mixture of W and Cr and WCr alloyed powders, followed by sintering and infiltration. Vacuum arcs on CuWCr composites were observed by a digital high-speed video camera. The morphologies of the composites before and after arc erosion were characterized by a scanning electron microscope. The results show that the microstructure CuWCr composites prepared by WCr alloyed powders becomes finer and more uniform, and, thus, has good characteristics of diffusive arcs and arc erosion resistance. In addition, the composite prepared by WCr alloyed powders has excellent electrical properties such as high breakdown voltage, low chopping current and long arc life. Arc erosion zones of the CuWCr composite fabricated by WCr alloyed powders become more dispersive and uniform on the surfaces with some shallow erosion pits. During the course of arc evolution, the dispersed arcs are caused by the split of electrical arc.

Effect of Internal Electrical Field on the Electrical Breakdown Properties of Contact Materials

In order to get a deep understanding of the effect of internal electrical field on the electrical breakdown properties of contact materials, two kinds of W-Cu and Cr-Cu joints were prepared in a vacuum sintering furnace. The vacuum breakdown tests were respectively performed at the interface of two joints and pure metal ends in an arc extinguishing chamber, and the surface morphologies after electrical breakdown 50 times were characterized by a scanning electron microscopy equipped with an energy dispersive spectroscopy. The results show that the breakdown strength at the interface is much larger than that of pure metal ends, and the breakdown site deviates from the interface. It is suggested that the existence of internal electrical field at the interface of two contact metals changes the electronic structure, and, thus, the electrical breakdown behavior is influenced.

Effect of Rare Earth Ce Addition on Microstructure and Properties of WCu Contact Materials

In order to clarify the effect of rare earth Ce on the microstructure and properties of WCu contact materials, different contents of Ce were introduced into W skeleton, and the relative density and compression stress of the pre-sintered W skeletons were tested. Subsequently, WCu contact materials with different contents of Ce were prepared by infiltration method. The hardness, electrical conductivity and the compression stress of WCu contact materials were tested, and the microstructure and composition were characterized by a scanning electron microscope equipped with an energy dispersive spectrometer. The results show that rare earth Ce can purify W/W interface and promote the densification of W skeleton, enhance the bonding of Cu/W, and improve the integral properties of WCu contact materials. In the range of experiments, WCu contact materials with 0.30wt%Ce addition has the maximum hardness of 215HB and the maximum compression stress of 900N/mm2, which are respectively increased by 23.60% and 57.20% in comparison with that without Ce addition.

Effect of Rare Earth Y Addition on the Properties and Precipitation Morphology of Aged Cu-Cr-Ti Lead Frame Alloy

The influence of rare earth Y addition and ageing treatment on the properties and precipitation morphology of Cu-Cr-Ti alloy was investigated. The results show that 0.1wt%Y addition increases the hardness, and decreases the electrical conductivity slightly. However, both the hardness and electrical conductivity decrease with an excessive Y addition. After ageing at 550°C for 2h, Cu-0.3Cr-0.2Ti-0.1Y alloy has a good combination of the hardness and electrical conductivity, which has the hardness of 134HV and the electrical conductivity of 73.9%IACS. After ageing treatment, most Cr rich phases precipitate in the form of sphere shape while a small amount of Cr rich phases exist in the form of acicular, and Y rich phases precipitate in the form of flake along the grain boundary.

Process of In Situ Cr Oxidation in Cu-Cr Pre-Alloyed Powders

The in-situ oxidation technique is an effective method of synthesizing copper matrix composites reinforced by oxide dispersion. In this study, the process of fabricating Cu/Cr2O3 composite by Cr in-situ oxidation in Cu-Cr pre-alloyed powders was investigated. The evolution of the structure formed in the processing of Cu/Cr2O3 composites was characterized by optical microscopy and transmission electron microscopy (TEM). The results show that the sub-solution Cu-Cr alloy powders can be produced by high energy milling, in which Cr powders are first crushed into fine particulates, followed by the formation of Cr sub-solution in copper under the extrusion and impact of high energy grinding balls. In the Cu/Cr2O3 composite fabricated by the Cu-Cr pre-alloyed powders, the Cr2O3 particulates produced exist almost in the original sites of the Cr, and they are dispersed uniformly within the Cu matrix. The distribution of Cr2O3 particulates is similar to that in the full solid solution Cu-Cr powders.

Effect of Melt-Casting Temperature on Bonding Zone of CuNiMnFe30CrMnSi Integral Material

The effect of melt-casting temperature on the microstructure and properties of transition interlayer for CuNiMnFe/30CrMnSi material was investigated in vacuum condition. The results show that the thickness of the transition layer and its bond strength increase, and then decrease with increasing temperature. At 1130 , the intermediate transition layer has the largest width, which is 132μm, and the tensile strength can reach up to 1322Mpa. In the intermediate transition layer, mutual diffusion occurs among these alloying elements. These elements, such as Cu, Ni and Mn, diffuse into 30CrMnSi and results in the formation of Fe base solid solution, and no harmful brittle phases are produced in the proximity of bonding interface, thus it has a good metallurgical bonding for the two materials.

Effect of La Addition in W Skeleton on Microstructure and Properties of WCu Alloy

In order to improve properties of WCu alloy, the different La were introduced into W skeleton during sintering process. The hardness, electrical conductivity and the compression stress were tested, and the microstructure and composition were characterized by a scanning electron microscope. The results show that an appropriate rare earth La addition can purify W/W interface, enhance the bonding of W /W, and improve the densification and the integral properties of WCu alloy. In the range of experiments, WCu alloy with 0.3wt% La addition has the largest hardness value of 198HB and the maximum compression stress of 823N/mm2. In comparison with that without La addition, 0.3wt%La addition decreases the electrical conductivity slightly, but improves the hardness and the maximum compression stress significantly, which are increased by 23.6% and 57.2%, respectively.

Effect of Al(Cr) Content on the Distribution of Al2O3(Cr2O3) Particles Formed by Internal Oxidation

This investigation was conducted to study the effect of Al(Cr) content in Cu-Al(Cr) pre-alloyed powders on the distribution of Al2O3(Cr2O3) particles formed by internal oxidation. The results show that the distribution of Al2O3 particles is different with the change of Al content in Cu-Al system. When the Al content is above 1.2wt.%, the Al2O3 particles tend to distribute along the grain boundaries of copper matrix , whereas when the Al content is above 2.0 wt.%, the Al2O3 particles have distributed along the grain boundaries. However, it is interesting to note in Cu-Cr system that most of the formed Cr2O3 particles prefer to distribute in the grain of copper matrix when the Cr content is less than 5wt.%, which is quite different from that of Cu-Al system.