Mechanical Properties And Irradiation Resistance Of CrMnFe(V?Ni)-Al High Entropy Alloys

In this paper,Al,V,Cr,Mn,Fe,Ni elements of medium and low neutron absorption cross-sections were select to design and prepare series of high entropy alloys with different crystal structures based on the atomic radius difference?,mixing enthalpy?H_mix,mixing entropy S_mix,valence electron concentration VEC and so on,through the empirical formulas.And their structure,mechanical properties,irradiation resistance and mechanism were systematically studied.The main results are as follows:(1)By adjusting the content of V and Ni elements,CrMnFeNi₂,V_0.1CrMnFeNi_0.9,VCrMnFe high-entropy alloys with FCC,FCC+BCC,and BCC structures were obtained.The compressive fracture strains of the three alloys all exceed 50%,and the yield strengths increase sequentially,respectively:44.9 MPa,250 MPa,and 660 MPa.(2)In the Al_xCrMnFeNi₂(x=0.3,0.8,1.0)high entropy alloy system,Al_0.3CrMnFeNi₂high entropy alloy still keeps a single-phase FCC structure,and the alloy have a good plasticity with a compressive fracture strain exceeding 50%,but the yield strength and hardness are very small,that is,229 MPa and 137 HV respectively;the crystal structure of Al_0.8CrMnFeNi₂ high entropy alloy is FCC+BCC+B2+a small amount of Fe Cr-rich phase,the precipitation of the second phase causes the compressive fracture strain to decrease to 40.6%,but the yields strength and hardness are significantly improved,reaching 836 MPa and 330 HV respectively;with the further increase of Al content,the crystal structure of Al_1.0CrMnFeNi₂ high entropy alloy is BCC+B2+a large amount of Fe Cr-rich phase,the compressive fracture strain drops to 35%,and the yield strength and hardness are 786 MPa and 421 HV respectively.(3)In the Al_xV_0.1CrMnFeNi_0.9(x=0.2,0.5,1.0)high entropy alloy system,the crystal structure of Al_0.2V_0.1CrMnFeNi_0.9 high entropy alloy is FCC+BCC+B2,the compressive fracture strain is 48.7%,and the yield strength and hardness are 696 MPa and 324.5 HV,respectively;the crystal structure of Al_0.5V_0.1CrMnFeNi_0.9 is BCC+B2,the compressive fracture strain is 45.8%,and the yield strength and hardness are 1104 MPa,and 403.2 HV respectively.The strengthening mechanism of the alloy was evaluated and the results showed that precipitation strengthening is the main strengthening mechanism;the crystal structure of Al_1.0V_0.1CrMnFeNi_0.9 is also BCC+B2,the compressive fracture strain is 7.5%,and the yield strength and hardness are 1226 MPa,543.5 HV,respectively,this is because the modulated microstructure causes stress concentration at the grain boundary,which leads to the occurrence of brittle fracture.(4)He⁺ irradiation experiments were carried on FCC-structured CrMnFeNi2,BCC-structured VCrMnFe and(BCC+B2)-structured Al_0.5V_0.1CrMnFeNi_0.9 high entropy alloys.The results showed that there was no phase transformation after the three alloys were irradiated,but with the increase of radiation fluence,the lattice constants of CrMnFeNi₂ high entropy alloys fluctuate the least,while the lattice constants of VCrMnFe and Al_0.5V_0.1CrMnFeNi_0.9high entropy alloys fluctuate greatly;under the irradiation condition of 3×10¹⁶ ion/cm²,the volume densities of helium bubbles of CrMnFeNi₂,VCrMnFe,Al_0.5V_0.1CrMnFeNi_0.9 high-entropy alloys are:8.57×10²³,3.80×10²³,2.32×10²³ m^-3,the helium bubble size is 2.09,3.00,3.60 nm,respectively;CrMnFeNi₂ alloy nano-hardness increases by 77.91%,VCrMnFe nano-hardness increases by 37.91%,Al_0.5V_0.1CrMnFeNi_0.9 nano-hardness increases by 13.14%,which has the best anti-radiation performance.