| As a non-ferrous metal material integrating structural and functional requirements,copper alloy is widely used in lead frame,high-speed railway electrical contact wire,conduction components and so on.To meet the requirements of high length,high strength and high conductivity of high-speed railway electrical contact wire,Cu-Cr alloy has become a research hotspot.To replace the Cu-Cr alloys containing high melt elements and burning loss elements,our research group developed Cu-Cr-In alloy,which can effectively improve the production efficiency and stability.In this thesis,developing new preparation and processing of Cu-Cr-In alloy,studying on the evolution of microstructure and properties of Cu-Cr-In alloy during preparation and processing,revealing the internal correlation between composition,processing,microstructure and properties are the main research contents,which are of great theoretical significance to the industrial production of Cu-Cr-In alloy.Cu-Cr-In alloy ingots were prepared by means of atmospheric smelting and iron mold casting.The primary phase morphology of as-cast alloy were observed by scanning electron microscope?SEM?.The solute atoms distribution during solidification was simulated by Scheil model.With the detection and analysis technique of transmission electron microscope?TEM?,high resolution transmission electron microscope?HRTEM?,and atomic probe chromatography?APT?,the influence of microstructure,properties,nano-Cr phase precipitation during aging were studied.The thermal deformation behavior of Cu-Cr-In alloy was studied by isothermal compression heat simulation.The influence of In on microstructure,properties,recovery and recrystallization of Cu-Cr-In were analyzed during“hot extrusion–drawing–solution–drawing–aging”.A continuous up casting short flowsheet process of Cu-Cr and Cu-Cr-In alloy was developed.The softening resistance and recrystallization of Cu-Cr and Cu-Cr-In alloy prepared by continuous up casting were studied.The influence of microstructure and properties during deformation and heat treatment of the Cu-Cr-In alloy were investigated.The strengthening mechanism were explained by the theoretical model formula.The solidification interval of Cu-Cr alloy was enlarged by adding In element.As the solidification interval of Cu0.34Cr0.18In alloy reach 214?,Cr atoms and In atoms are enriched at the front edge of solid-liquid interface during solidification,and the elongated eutectic Cr phase was replaced by dendritic divorced eutectic.After solid solution and aging,the peak hardness of Cu0.34Cr0.18In alloy is 140 HV,which is about 4 HV higher than Cu0.34Cr alloy.In atoms are mainly solid dissolved in alloy matrix,and there are no obvious effect on the precipitation Cr phase during aging.The precipitation sequence of Cu-Cr-In alloy at 450?is supersaturated solid solution?fcc Cr phase?bcc Cr phase.The Cu-Cr-In alloy was sensitive to the deformation temperature and strain rate.The flow stress increased with the rise of the strain rate and decreased with the rise of the deformation temperature during hot deformation.The function of Cu0.45Cr0.1In alloy hot deformation constitutive equation was established.The optimal hot deformation conditions of Cu-Cr-In alloy lie in the range of 850?900?and strain range of 0.01 s-10.1 s-1.The peak aging strength of Cu0.59Cr,Cu0.54Cr0.17In alloy rods obtained by“drawing–solution–drawing-aging”are 470.51 MPa,497.90 MPa respectively.The phase distribution and dislocation density of the Cu-Cr and Cu-Cr-In alloy were basically the same,and the increase in strength after adding In were mainly caused by the combination of solid solution strengthening of In atoms and the grain strengthening.In can hinder the movement of dislocation,slow down the reduction of dislocation density,delay the recovery and recrystallization of the deformation Cu-Cr-In alloy during high-temperature annealing,so as to significantly improve the annealing hardness and softening resistance temperature.The softening resistance temperature of Cu0.54Cr0.17In alloy is 560?,and the activation energy for recrystallization of 59.59%drawn Cu0.54Cr0.17In alloy is estimated to be 188.29±18.44kJ/mol.With the same process,the Cu-Cr,Cu-Cr-In alloy prepared by continuous up casting have lower deformation energy storage and more evenly distributed of Cr atoms than the alloys prepared by hot extrusion.At the same temperature,the recovery and recrystallization ratio of Cu0.3Cr and Cu0.26Cr0.1In alloy prepared by continuous up casting was lower,and the precipitation Cr phase are more evenly distributed and grows more slowly than the Cu0.59Cr and Cu0.54Cr0.17In alloy prepared by hot extrusion.Therefore,the hardness of Cu0.3Cr and Cu0.26Cr0.1In alloy are about 27 HV and 20 HV higher than Cu0.59Cr and Cu0.54Cr0.17In alloy at 580?and 660?respectively.The activation energy for recrystallization of 59.59%drawn Cu0.26Cr0.1In alloy is estimated to be 232.32±13.38kJ/mol.The Cr atoms solid solution into Cu matrix during continuous up casting of Cu-Cr-In alloy,and non-solution heat treatment is needed.With the increase of strain during cold draw,the dislocation density increment is different,and the increase rate decreases with the increase of dislocation density.A novel strengthening route excluded a solution heat treatment and allowed aging prior to the deformation processes for upward continuous casting of Cu0.26Cr0.1In alloy rods,and the tensile strength reached 558.98 MPa.Theoretical calculations and microstructural characterization confirm that deformation strengthening play the key role in the processing route. |
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