Effect On Microstructures And Properties Of Cr And Al Elements On FeCoCrNiAl High Entropy Alloy

High entropy alloys（HEAs）are favored by the scientific community for high strength and plasticity,high wear resistance,good corrosion resistance,and excellent magnetic properties.The HEAs have cocktail effect and the mechanical properties can be improved by adjusting the composition.In addition,traditional magnetic materials have excellent magnetic properties and poor processing properties,which limits applications.HEAs have excellent magnetic properties and high plasticity.The effect of the changes in element content on the microstructures and properties of the alloy is studied.This study can obtain HEAs with excellent comprehensive properties.The research has important theoretical significance for promoting the application of HEAs in engineering materials and magnetic materials.Based on FeCoCrNiAl alloy,the contents of Cr and Al were adjusted to optimize the composition.These alloys were melted to uniformity by water-cooled copper crucible induction melting furnace.The plate-shaped specimens were fabricated by a copper mold.Some as-cast specimens were processed by cold rolling and annealing.These experiments can obtain specimens in two states.These specimens were divided into as-cast and annealed after cold rolling.The specimens were tested by X-ray diffraction,optical microscope,scanning electron microscope,mechanical properties testing,electrochemical experiment,vibration specimens magnetometer and resistance meter.The structure,phase composition,mechanical properties,corrosion resistance,magnetic and electrical properties of alloys can be able to analyze.The results show that the crystal structures of Fe_1.25CoCr_x Ni_1.25Al_0.25（x=0.5,0.75,1.0）and Fe_1.25CoCrNi_1.25Al_x（x=0.1,0.25,0.4）consist of single-phase FCC solid solution.In the mechanical experiments,the strength of as-cast alloys is below 200MPa when the elongation of as-cast alloys is above 50%.After cold rolling and annealing,the strength and hardness of alloys increases with the increase of element content.However,excessive Al element has a negative effect on the plasticity of alloys.Fe_1.25CoCrNi_1.25Al_0.25 has the best comprehensive mechanical properties.The yield strength,tensile strength,and hardness are 498 MPa,770 MPa,and 260 HV when the elongation is 40%.In electrochemical experiments,the appropriate amount of Cr element makes the HEAs form more stable oxide film,which can improve the corrosion resistance of alloys.Fe_1.25CoCr_0.75Ni_1.25Al_0.25 shows excellent corrosion resistance after rolling and annealing.The current density of Fe_1.25CoCr_0.75Ni_1.25Al_0.25 is 4.27×10^-7A/cm² in 0.5 mol/L H₂SO₄ when the current density of the alloy is 1.96×10^-6A/cm² in 3.5%NaCl.In magnetic experiments,the reduction of Cr content is helpful to improve the soft magnetic properties of alloys.Fe_1.25CoCr_0.5Ni_1.25Al_0.25shows excellent magnetic properties after rolling and annealing.The coercivity of Fe_1.25CoCr_0.5Ni_1.25Al_0.25 is 1.26 Oe and the saturation magnetization of the alloy is about 51.29 emu/g.At the same time,the alloy also has good processability with the elongation of 62%.