The Study Of Microstructure,Mechanical And Corrosion Properties Of Al_xCoCrCu_0.5FeNiMo_y High-Entropy Alloys

High-entropy alloys has broken the alloy design concept of traditional alloys with one or two elements as the main elements.Through the combination of different elements and the adjustment of the ratio,high-entropy alloys with high strength,high plasticity,wear resistance,corrosion resistance and excellent electromagnetic properties can be obtained,which makes high-entropy alloys have great academic research value and wide application prospects.In this paper,Al_xCoCrCu_0.5FeNi high-entropy alloys were prepared by vacuum arc furnace.The microstructure of the alloys was studied by XRD and EPMA.The mechanical properties of the alloys were studied by microhardness test and compression test at room temperature.The corrosion resistance of the alloys was studied by potentiodynamic polarization test and EIS test.Based on the Al_0.1CoCrCu_0.5FeNi high-entropy alloy with good comprehensive mechanical properties,the influence of Mo element on its microstructure,mechanical properties and corrosion resistance was studied by adding a small amount of Mo element.The study found:（1）The high entropy effect brought by the mixing of various elements makes the structure of Al_xCoCrCu_0.5FeNi high-entropy alloy relatively simple.The alloys have a dendritic structure,and is composed of the FCC phase and the FCC-structured Cu-rich phase The Al_xCoCrCu_0.5FeNi high-entropy alloys have good plasticity and the compression ratio exceeds50%.Its microhardness and yield strength increase with the increase of Al content.The microhardness and yield strength of Al0.5 alloy reach 217HV and 301MPa.However,the addition of Al element increases the E_corr and the I_corr of the alloys,which increases from-193mV and 3.66μA/cm² of Al0 alloy to-206mV and 6.39μA/cm² of Al0.5 alloy,respectively.（2）After adding a small amount of Mo element,the Al_0.1CoCrCu_0.5FeNiMo_y high-entropy alloys still have a dendritic structure,but the phase composition is changed from the original FCC matrix phase+the Cu-rich phase with FCC structure to the FCC matrix phase+σphase.Similarly,the Al_0.1CoCrCu_0.5FeNiMo_y high-entropy alloys have good plasticity and a compression ratio of more than 50%.With the addition of Mo element,the Vickers hardness and yield strength of the alloy are interrupted.The microhardness and yield strength of Al0.1Mo0.5 alloy are 278HV and 346MPa respectively.Solid solution strengthening and second phase strengthening are the main reasons for the improvement of mechanical properties.The addition of Mo element improves the corrosion resistance of Al_0.1CoCrCu_0.5FeNiMo_y high-entropy alloys.With the increase of Mo content,the E_corr of the alloy increases first and then decreases,but the scope of change is small.The E_corr of Al0.1Mo0.1 alloy is the highest,which is-187mV.The I_corr is always reduced,and the I_corr of Al0.1Mo0.5 is the smallest,being1.92μA/cm²,which is 1/3 of the Al0.1M0 alloy.The addition of Mo element significantly increases the passivation interval of the Al0.1Mo0.3 alloy and the Al0.1Mo0.5 alloy.The EIS results also shows that the equivalent resistance of the passivation film of Al0.1Mo0.3 alloy and Al0.1Mo0.5 alloy is greater than that of Al0.1Mo0 alloy and Al0.1Mo0.1 alloy.Al0.1Mo0.3 alloy has good comprehensive mechanical properties and good Cl^-corrosion resistance.