Hot Deformation Behavior And Microstructure Control In Dual-phase Al_0.6CoCrFeNi High Entropy Alloy

In recent years,high entropy alloys（HEAs）have received considerable attention because of their simple crystal structures and outstanding properties.However,the HEAs prepared by the melt casting route usually exhibit dendritic microstructure with component segregation.In addition,the drawbacks of cast alloys restrict the mechanical performances and applications.Thus,it is meaningful to identify the optimum thermo-mechanical processing and modification technology in microstructure.The present study focused on the hot deformation behavior and microstructure control of a dual-phase Al_0.6CoCrFeNi HEA.Based on the Gleeble3500 thermal simulator,hot deformations with different temperatures and strain rates were carried out.Complementary microstructural analysis and mechanical properties of the deformed alloy were discussed.Constitutive equation which reflects the relationship between the temperature,strain rate,and flow stress was established.Power dissipation efficiency and deformation instability maps were obtained by utilizing the dynamic materials model.Additionally,in order to realize microstructure control,heat treatments were executed on the deformed alloys.During the hot deformation,the flow stress of the Al_0.6CoCrFeNi dual-phase HEA decreases with the increase of temperature and the decrease of rate.The morphology of BCC phase changes with the increase of temperature or strain rate.The softening mechanism during the deformation is dynamic recovery.The thermal deformation equation is:（?）where?(5=（?）exp?（395660/）.According to the processing map,the best hot working range is 900-1000℃,10^-1-1s^-1.The alloys after deformation and annealing have significant change in microstructure and mechanical properties.The deformed alloys exhibited uniform recrystallized exuiaxed grains in both FCC and BCC phases after further annealing at high temperature for a long time.The yield strength of the tempered alloy increases with the increasing annealing hours and the decreasing aging temperature.The alloy with equiaxed grains in dual-phase was successfully obtained after optimizing the parameter of deformation and annealing.The tensile elongation of the alloy can be increased from 17%to 35%.The optimum process route is:deformed at 900℃,10^-3s^-1,annealing at 1200℃for 20h.