Effect Of Carbon Element And Heat Treatment On Microstructure And Properties Of AlCrFe₂Ni₂C_x High Entropy Alloy

High entropy alloys?HEAs?have attracted extensive attention due to its high hardness,high strength,good wear resistance and excellent corrosion resistance.The influence of element types and contents on the microstructure and properties of alloys has become an important task for people to research and excavate.The effect of heat treatment on the microstructure and properties of HEA has important research significance.Therefore,the HEA with excellent properties can be obtained by adjusting the alloy element content and the temperature of annealing treatment,which has a good theoretical guidance and reference significance for future scientific research.AlCrFe₂Ni₂ high entropy alloy has FCC+BCC dual-phase solid solution structure.In this paper,the alloy was selected as the matrix to investigate the influence of different carbon content and annealing treatment on the microstructure transformation and mechanical properties of the AlCrFe₂Ni₂C_x biphasic HEA.The vacuum arc smelting furnace was used to prepare the specimen of button ingot.Determine the annealing temperature by DSC.The effects of carbon content and annealing treatment on phase composition and microstructure structure of AlCrFe₂Ni₂ HEA were analyzed by XRD,SEM,EDS,TEM and EBSD.At the same time,the room temperature compression properties and hardness of the alloy were tested.The results show that carbon addition induced the growth and aggregate of disordered noodle-like FCC phases.The volume fraction of the FCC phase increases from 33.2%to51.2%as the C content increases.The Al and Ni in the alloys were segregated at the phase boundaries.Disappearance of the spinodal decomposition structure compose of a disordered BCC structure and an ordered BCC structure?B2?.The BCC phase transform into a spherical B2 phase with increasing C content.The yield strength of the HEAs was closely related to the volume fraction of BCC phase as the C content increases.The?phase?Cr,C carbonization?precipitate in an FCC phase when the C content is above 2.0 at.%.The hardness of the HEAs increases from 310 HV to 357 HV as the C content increases.The compressive strength and the fracture strain of the alloy decreases as the C content increases.Fracture mechanism changes from ductile to brittle fracture.After annealing of AlCrFe₂Ni₂C_x alloy at 600?,the yield strength and hardness of the alloy system are the highest,and the fracture strain is the lowest.After annealing at 850?,the yield strength and compressive strength of the alloy system have increased.Carbide precipitates at the phase boundary between the FCC phase and the BCC phase,and a new phase precipitates in the combined FCC phase,which improves the overall mechanical properties of the alloy.After annealing at 950°C,the precipitates grow up and the mechanical properties of the alloy system decrease.