| With the excellent electrical and thermal conductivities, corrosion resistance,higher strength and fatigue resistance, Cu-Cr-Zr alloy is widely applied in integratedcircuit lead frame, casting crystallizer, trolley wire, electric locomotive overheadconductor, etc. At present, research on Cu-Cr-Zr alloy has mostly focused on agingproperties and microstructures. But the unified agreement with precipitates categoryhas not been arrived, and the report on hot deformation behavior of Cu-Cr-Zr alloy hasbeen rarely seen.In this paper, the effects of thermomechanical treatment technological parameterson microhardness and electrical conductivity of Cu-Cr-Zr alloy were studied.Precipitates morphology and category was analyzed. According to the electricalconductivity changes of solid-solution Cu-Cr-Zr alloy in the aging treatment and therelationship between electrical conductivity and precipitates amount, the Avrami phasetransformation kinetics and electrical equations of the alloy after aging treatment atdifferent temperatures were determined, and the isothermal transformation kineticscurve was drawn. The flow stress behavior of Cu-Cr-Zr alloy was studied by thermalsimulation test on the Gleeble-1500thermal-mechanical simulator. The influence ofdeformation temperature and strain rate on flow stress was investigated, the hotdeformation activation energy was calculated and the constitutive equation andprocessing maps were established. Then microstructure evolution after deformationwas observed and the optimum technological parameter was found.The results show that, a better comprehensive performance was obtained for thesolid-solution alloy aged at450°C for4h, the microhardness and electricalconductivity of the alloy rised to156.5HV and82.6%IACS, respectively. There wascoherent face-centered cubic Cr-phases with lobe-lobe contrast existing in the alloyaged at450°C for4h. The face-centered cubic Cr-phases transformed into body-centered cubic Cr-phases, when aging time prolonged to8h. The dispersedprecipitates in the alloy aged at550°C for2h were identified as body-centered cubicCr-particles and Cu4Zr-particles, and the Cr-particles exhibited the N-W orientationrelationship with the Cu matrix. According to the electrical conductivity changes in theaging treatment and the relationship between volume fraction of precipitates and time,the Avrami equation of phase transformation kinetics and the electrical conductivityequation at different temperatures were obtained. On the basis of the experiment dataof thermal simulation, the influence of deformation temperature and strain rate on flowbehavior of the Cu-Cr-Zr alloy was investigated. The constitutive equation wasestablished and the hot deformation activation energy was calculated as173.85kJ/mol.Through processing map being established and deformation microstructure beingobserved, three safe processing zone and the optimum domain occurred at770~850°Cand0.01~0.82s-1with the efficiency of power dissipation of23%~40%for hotworking was obtained. |
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