Research On Hot Deformation Behavior And Rolling Process Of The Extruded CuCr25Alloy

By far, Cu-Cr alloy has been the most ideal and the most widely used vacuumcontactor material of middle or high pressure resistance because of its high strength,high hardness, good thermal conductivity electrical conductivity and strong corrosionresistance. In order to develop an efficient route of Cu-Cr alloy contactor process,including such four steps as ingoting, extruding, rolling, and blanking, the Cu-Cr25alloy was selected to study its hot deformation behavior at high temperature and therolling and aging process in this paper: for studying its hot deformation behavior athigh temperature, Isothermal compression tests of the extruded CuCr25alloy werecarried out on Gleeble-3500system; Isothermal compression tests of the extrudedCu-Cr25alloy were carried out on Gleeble-3500system. The hot deformation behaviorof alloy was studied, based on which effects of the rolling temperature and reduction ineach pass on the microstructures and properties of the extruded Cu-Cr25wereinvestigated; moreover, aging heat treatment of the rolled Cu-Cr25was carried out toexplore the optimal technology. Results were as following:When the extruded Cu-Cr25alloy processed isothermal compression deformation,the flow stress increased with the increase of strain rate and the decrease ofdeformation temperature, and its microstructure had the phenomenon of dynamicrecrystallization. The flow stress behavior of the extruded Cu-Cr25alloy could bedescribed by the Zener-Hollomon parameter Z in hyperbolic-sine equation with theaverage hot deformation activation energy Q being383.4kJ/mol.According to the dynamic model (DMM) and microstructure analysis, when theStrain was0.4and0.6, the instability area of the processing maps of the extrudedCuCr25alloy changed little but at high temperature and high strain rate, its instabilityhappened easily. Though the Strain increased, power dissipation factor changed little.The optimum processing parameters of Cu-Cr25were830℃~900℃for its deformationtemperature and0.01~0.1s-1for its strain rate.In the rolling process of the extruded CuCr25alloy, dynamic recrystallizationoccurred. As the rolling temperature increased, the microstructure of alloy refined, itshardness increased, but its conductivity reduced. The best rolling process parametersof the alloy was900℃for the rolling temperature and45%for the reduction in each passé. At this time, the Brinell hardness reached the peak value108.7HB, theconductivity reached43.27%IACS, and the microstructure reached its minimum2-5μm.The Comparison of directly aging with solid solution plus aging treatment processshowed that: in the aging process, as the aging temperature increased, the Brinellhardness and the conductivity increased to their peak, after which they began todecline; as the aging time extended, the Brinell hardness and the conductivity ofdirectly aging first increased and then remained stable, with the peak being127.2HBand53.5%IACS respectively; the Brinell hardness of solid solution plus aging firstlyincreased to the peak, after which it declined and the conductivity firstly increased,and then remained stable with the peak being136.2HB and52.8%IACS respectively;the increase of hardness was mainly related to the precipitation strengtheningmechanism and the improvement of conductivity was mainly derived from theprecipitation of Cr; under this experimental condition, the best aging processparameters of the rolled Cu-Cr25alloy were920℃+1h for solid solution and510℃+2hfor plus aging; on this condition, the hardness and electrical conductivity of the rolledCu-Cr25alloy could reach or even surpass the requirements of application of the alloycontact material.