Study On The Modification Of AlCoCrFeNi_2.1 High Entropy Alloys By Al And Fe ?Co? Elements

In recent years, the high entropy alloys have developed rapidly with some alloy systems being developed successively with excellent mechanical properties. Among these, AlCoCrFeNi is one of the most studied high entropy alloys. The research of AlCoCrFeNi2.1 high entropy alloy with eutectic morphology is based on AlCoCrFeNi HEA. Its excellent plasticity and strength have attracted widespread attention. But the impact of elements content changes on AICoCrFeNi2.1 HEA is rarely studied. So, in this paper, the microstructures and mechanical properties have been studied, through the methods of changing the content of Fe?Co? element and Al element of the AlCoCrFeNi system high-entropy alloy.In order to study the microstructure, organizational structure, compression performance, micro hardness, the samples of the two series of high entropy alloys ?AIxCoCrFeNi2.1? AlCoxCrFe2-xNi2.1?were prepared by vacuum arc furnace. The experimental results are as follows:?1?For the AlCoCrFeNi_2.1?x=0,0.2,0.4,0.6...2.0? HEAs:With the increase of Al element the microstructure changes from FCC structure to FCC+BCC mixing structures.The values of yield stress and fracture strength increase with the emerging of BCC phase,while plastic strain declines at the same time,and the fracture mechanism changes to brittle fracture when x is 2.0.For Al1.2CoCrFeNi2.1 HEA, the yield stress, fracture strength, and plastic strain are as high as 851.0 MPa,1983 MPa, and 31.2%, respectively,which means that it has good comprehensive mechanical properties. What's more,the hardness of AlCoCrFeNi_2.1 HEAs increases with the addition of Al element, for the lattice distortion of the alloys and the formation of a hard BCC phase.?2?For the AlCoxCrFe2-xNi2.1?x=0,0.2,0.4,0.6,0.8,1.0?HEAs:With the increase of Fe element the microstructure changes from FCC+B2 structures to FCC+B2+BCC mixing structures as x is less than 0.4. The content of BCC structure increases with the addition of Fe element. When x reaches 0.2, the eutectic morphology disappears. For AlCrFe2Ni2.1 HEA, the yield stress, fracture strength, and plastic strain are as high as 733.1 MPa,2832 MPa, and 52.0%, respectively. The excellent mechanical properties of the alloy are attributed to the spinodal decomposition of BCC phases and the composite effect of the softer FCC and harder BCC phases.