| QCrO.8 alloy is a Cu-Cr binary alloy with a Cr content of 0.6-0.9 wt.%.It has good electrical and thermal conductivity,high strength and softening temperature,good fatigue performance and certain corrosion resistance.It is commonly used in vacuum manufacturing contacts,integrated circuit lead frames,resistance welding electrodes,mold liners,and the inner wall of the rocket engine combustion chamber.Since QCr0.8 alloy is an alloy with Cr phase precipitation strengthening as the main strengthening mechanism,it is necessary to control the morphology,size and distribution of Cr phase in the matrix in order to obtain alloys with excellent mechanical properties and excellent electrical and thermal conductivity.In this paper,the microstructure and properties of QCr0.8 alloy were controlled by solid solution+multi-directional hot compression+aging deformation heat treatment process in order to obtain an alloy with excellent comprehensive properties.In this paper,the thermal compression experiments of QCr0.8 alloy were carried out,and the flow stress behavior,constitutive equation,thermal processing diagram,dynamic recrystallization critical condition and thermal compression microstructure evolution of the alloy were studied to provide a theory for the multi-directional thermal compression experiment of the alloy.Then,the multi-directional compression experiment was designed to test the alloy under different conditions.The multi-directional compression samples were heat treated.The microstructure evolution of the alloy after multi-directional compression under different conditions was studied by OM,SEM and EBSD.The properties of the alloy were studied by tensile test,hardness and electrical conductivity tests.The main conclusions obtained are as follows:(1)Under the condition of 750-900 ℃,strain rate of 0.01-10 s-1 and total compressive deformation of 50%,the true stress-true strain curve of the alloy shows the interaction characteristics of work hardening and dynamic recrystallization softening.The temperature and strain rate have obvious influence on the peak stress of the alloy.When the temperature is constant,the peak stress of the alloy increases with the increase of strain rate.When the strain rate is constant,the peak stress of the alloy decreases with the increase of temperature.(2)The thermal deformation activation energy Q of QCr0.8 alloy is obtained by the hyperbolic sinusoidal function model,and its value is 370.8 kJ/mol.The constitutive equation of the alloy is constructed by the hyperbolic sine function model;The optimum thermal deformation conditions are 840-900 ℃,5.0-10 s.1.Fitting the dynamic recrystallization critical strain model of the alloy.(3)In the process of thermal compression,as the deformation pass increases,the second phase of the alloy appears to be refined;increasing the multi-directional compression deformation pass can increase the dynamic recrystallization volume fraction of the alloy,and increase The proportion of large angle grain boundaries.(4)The tensile strength and elongation of the samples after multi-directional hot compression of the deformation fluxes of 30%and 50%are not much different,but the hardness of the alloy decreases with the increase of the deformation pass.The conductivity of the alloy changed little after multi-directional compression under different conditions,and the alloy had a dimple at the fracture after stretching,and all showed ductile fracture.(5)The multi-directional compression sample with 50%pass deformation and 6 passes deformation is solid solution at 900℃/lh,and has the best performance after aging at 450 ℃ for 4 h.Its hardness reaches 102 HV and the conductivity reaches 96%IACS.The hardness of the hot extruded state was increased by 67.2%;the electrical conductivity was increased by 31.3%. |
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