Study On Structure And Property Of The WC/Cu-Al₂O₃Contactor Material

Al₂O₃/Cu-WC composite is one type of copper-based particles reinforced material,which is used in a variety of applications, such as electrical contact materials,resistance welding electrode, IC lead frame and so on, because of its excellentproperties of the electrical conductivity, thermal conductivity, high hardness andstrength at elevated temperature. At present, less research on the preparation processand performance of the both Al₂O₃and WC reinforced copper-based composites hasbeen investigated.In this work, the Al₂O₃/Cu, Al₂O₃/Cu-10vol%WC and Al₂O₃/Cu-20vol%WCcomposites were successfully prepared by the vacuum hot-press sintering and internaloxidation methods. The electrical conductivity and microhardness of the compositeswere determined and the microstructure was analyzed. The influence of the WCcontents of the composite on the microstructure and properties was also investigated.The hot deformation behavior of the composites under isothermal compressioncondition was investigated by means of a thermo-simulator system Cleeble1500D,and then on the basis of the results, the constitutive equations were established. Basedon dynamic materials model （DMM）, the processing maps of the composites were alsoestablished. The tribological experiments were carried out on a pin-on-disc typecurrent-carrying tribo-tester. The morphologies of the wear surface and thelongitudinal section and chemical composition of pin samples were examined by useof a scanning electron microscopy （SEM） and an energy dispersive spectroscopy（EDS）, respectively. The effects of current density and load on the tribologicalperformance and the wear mechanism of the composites were also investigatedrespectively.The results show that,1) the relative densities of the Al₂O₃/Cu, Al₂O₃/Cu-10vol%WC and Al₂O₃/Cu-20vol%WC composites as sintered are higher than95%andthe electrical conductivities are49.1%IACS,47.8%IACS and41.3%IACS, respectively. The electrical conductivity decreases with increase of the WC content.The microhardness of the composites is139HV,154HV and189HV, respectively. Themicrohardness increases with increase of the WC content.2) According to the hightemperature deformation stress-strain curves of the three composites, it is concludedthat the softening mechanisms are dynamic recovery and dynamic recrystallization.The hyperbolic sine equations including stress σ were adopted to describe the thermalactivated deformation behavior,i.e. the relationship of flow stress, deformationtemperature and stain rate of these three composites under different conditions.According to the calculations of the thermal deformation activation energy, the relativeconstitutive equations of composites were established. The processing maps werecalculated and constructed according to the dynamic materials model. Based on theprocessing map, the optimal processing parameters of the composites during thermaldeformation and the thermal deformation rheological instability area were proposedand determined respectively.3) Under the test conditions, the wear rate and frictioncoefficient of the composites increase with the current intensity increases. When thecurrent intensity is invariant, the wear rate and friction coefficient increase as the loadincreases. As the current and load remain constant, the wear rate and frictioncoefficient decrease with increase of the WC content. In the case of the current–carrying, due to the frictional heat, the contact resistance heat and the combined effectof the arc heat, a part of the composite matrix melted and or gasified resulting in theWC particles exposed on the worn surface. The wear mechanisms of the composite pinspecimens are mainly in the form of adhesive wear, abrasive wear and arc erosionunder the current-carrying conditions.