Effect Of Alloying Elements Ti?Cu On Microstructure Evolution And Properties Of AlCrFeNi High Entropy Alloys

High-entropy alloys prepared from five or more elements with equal or near equal ratio have attracted much attention due to their excellent properties.Al Co Cr Fe Ni Ti_(x)HEAs and Al Cr Fe Ni Ti Cu_(x)HEAs were prepared by non-consumable vacuum arc furnace.The influence of alloying elements Ti?Cu on the microstructure,corrosion and friction properties of HEAs were investigated by the metallographic microscope,XRD,SEM-EDS,MFT-EC4000 reciprocating friction and wear tester,DSC and electrochemical workstation.The results show that:Al Co Cr Fe Ni Ti_(x)HEAs were prepared and the effects of Ti on the structure,microstructure evolution,friction and corrosion properties of HEAs were studied.(1)According to the HEAs theory results,the addition of Ti can reduce?H_mix,increase?,reduce VEC and stabilize the BCC solid solution.(2)The addition of Ti makes the microstructure change from single BCC1 phase to coexistence of BCC1 and BCC2 phase.As the Ti content increases,the lattice distortion effect increases.(3)Ti element can refine the microstructure,which makes the microstructure change from coarse dendrite to fine equiaxed dendrite.When x>0.6,the size of equiaxed dendrites increases with the increase of Ti content.(4)With the increase of Ti content,the solution strengthening effect increases,but the defect concentration in the alloy increases.The synergistic effect of the two makes the hardness of the alloy increase first and then decreases,reaching the maximum value of 520.2 HV at x=0.8.The volume wear capacity is inversely proportional to the hardness.The main wear mechanism gradually changes from abrasive wear and oxidative wear to abrasive wear,oxidative wear and adhesive wear.(5)Al Co Cr Fe Ni Ti_(x)HEAs exhibits excellent corrosion resistance in 3.5%Na Cl solution and 0.5mol/L H₂SO₄ solution.With the increase of Ti content,the corrosion resistance of the alloy first increases and then decreases in solutions.When x=0.6,the corrosion resistance of HEAs is the best.Al Cr Fe Ni Ti Cu_(x)HEAs were prepared and studied to reveal the influence of Cu on the microstructure,friction and corrosion properties(1)The theoretical prediction results show that Cu element increases the?H_mix,decreases?,increases VEC,which promotes the formation of FCC phase.(2)With the increase of Cu content,the microstructure of the alloy changes from BCC phase to coexistence of BCC and FCC phases.Cu promtes the segregation of elements.Al,Ni and Ti elements segregate in the dendritic to form BCC solid solution,Fe,Cr elements and Cu element segregate in the interdendritic to form BCC and FCC solid solution,respectively.(4)With the increase of Cu content,the content of FCC phase in the alloy increases,the slip resistance decreases and the average friction coefficient decreases,which makes the wear mechanism of the alloy change from abrasive wear and oxidation wear to adhesive wear and oxidation wear.At the same time,the hardness of the alloy decreases monotonously with the increase of Cu content,and the variation of volume wear is not obvious.(5)With the increase of Cu content,the segregation of elements increases,which makes the corrosion resistance of the alloy decrease in 3.5%Na Cl solution.In 0.5mol/L H₂SO₄ solution,the copper rich phase as passive film improves the local pitting resistance of the alloy.