Fabrication And Properties Of Nano And Micron Hybrid Al₂O₃Particles Dispersion Strengthened Copper Base Composites

Because of high performance with high electrical and thermal conductivity, highstrength and hardness, as well as excellent thermal stability, the Al₂O₃-oxidationdispersion strengthened copper （ODSC） composites have been widely applied in thefields of resistance welding as electrode, electrical contact materials replacing thesilver-based composites, integrated circuit lead frame and so on. Recently, the study ofAl₂O₃-ODSC composites is mainly focused on the manufacturing technology and theproperties, while the hot deformation behaviors of Al₂O₃-ODSC composites have notbeen widely investigated at home and abroad.The nano and micron hybrid Al₂O₃-ODSC composites were prepared by vacuumhot-press sintering and internal oxidation method under the condition of sinteringtemperature of950℃for2hrs, compaction pressure of30MPa and vacuum of5×10-3Pa in this paper. The effects of different Al₂O₃content on the microstructure andproperties of Al₂O₃-ODSC composites were discussed respectively. The hotdeformation behaviors of the composites were carried out with a Gleeble-1500Dthermal simulator with isothermal compression test. On the basis of the above results,the hyperbolic sine constitutive equations were established based on the dynamicmaterial model （DMM）. The processing maps of the composites were also establishedfor the optimizing processing parameters of the ODSC composites during thermaldeformation. The friction and wear experiment were carried out on the hightemperature atmosphere tribo-tester, the effects of the temperature and chemicalcomposition of the composites on the wear rate and friction coefficient were alsoinvestigated, respectively.The results show that:（1） The relative densities of the ODSC,0.3%Al₂O₃-ODSC,0.6%Al₂O₃-ODSC and0.9%Al₂O₃-ODSC composites as sintered are higher than97%with the adding Al₂O₃dispersion uniformly distributed in the ODSC matrix. The hardness and the electrical conductivity are about162.5¹76.5HV and63.8⁵8.1%IACS, respectively. The hardness increases with the increase of the Al₂O₃content while the electrical conductivity decreases.（2） The true stress-strain curves ofthe ODSC composites present the typical dynamic recrystalization characteristics.With the strain increasing, at beginning the true stress increases quickly and thendecreases slowly till reaching a stable condition. According to the calculations of thethermal deformation activation energy, the hyperbolic sine constitutive equations ofthe ODSC composites were established respectively. Based on the processing mapswhich were calculated and constructed according to the dynamic material model, theoptimal processing parameters of the ODSC composites during thermal deformationwere proposed and the rheological instability zones were also determined, respectively.（3） The wear rate of the Al₂O₃-ODSC composites increase slightly and the frictioncoefficient decrease with the Al₂O₃content increase. The wear rate and the frictioncoefficient decrease with the temperature increase and especially reduce sharply abovethe temperature of300℃. The wear mechanisms of the Al₂O₃-ODSC composites aremainly in the form of adhesive wear and abrasive wear.