CoCrFeNi high entropy alloy(HEA)has attracted extensive attention due to its excellent corrosion resistance,but the low strength limits its engineering application prospects.In order to develop CoCrFeNi based HEAs wit...CoCrFeNi high entropy alloy(HEA)has attracted extensive attention due to its excellent corrosion resistance,but the low strength limits its engineering application prospects.In order to develop CoCrFeNi based HEAs with high strength,ductility and corrosion resistance,the effects of Zr content on the microstructure,mechanical properties and corrosion resistance of heterogeneous CoCrFeNiZr_(x)(x=0,0.25,0.5 and 1)HEAs were investigated in this work.The results indicate that the increase of Zr content can significantly affect the phase stability of the alloy,and promote the formation of intermetallic compounds(Ni_(7)Zr_(2)and/or Laves phase)and the transformation of solid solution from face-centered cubic(FCC)structure(x=0,0.25 and 0.5)to body-centered cubic(BCC)structure(x=1).Reasonable control of the Zr content can endow the alloy excellent comprehensive properties.Especially,for CoCrFeNiZr_(0.25) alloy,composed of FCC matrix and a small amount of Ni_(7)Zr_(2)phases,the yield strength(~655 MPa)is increased by nearly four times higher than that of Zr-free alloy,and it also has good ductility(fracture stain>50%).Meanwhile,the corrosion resistance of CoCrFeNiZr_(0.25) alloy is better than that of SS304.The EIS results show that the addition of Zr reduces the stability of the passive film on the alloy,which can be related to the content of the beneficial oxide in the passive film and the thickness of the passive film through XPS analysis.Moreover,the work functions of different phases in CoCrFeNiZr_(x)alloys were obtained by firstprinciples calculations,which further confirmed the selective corrosion mechanism of the CoCrFeNiZr_(x) alloy combining the experimental results.展开更多
A detailed theoretical study on structural,electronic and optical properties of Mg2Si under the isotropic lattice deformation was performed based on the first-principles pseudopotential method.The results show that th...A detailed theoretical study on structural,electronic and optical properties of Mg2Si under the isotropic lattice deformation was performed based on the first-principles pseudopotential method.The results show that the isotropic lattice deformation results in a linear decrease in the energy gap for the directΓ15-Γ1 and indirectΓ15-L1 transitions from 93%to 113%,while the indirect band gapΓ15-X1 increases from 93%to 104%and then reduces over 104%.When the crystal lattice is 93%compressed and 113% stretched,the magnesium silicide is a zero-gap semiconductor.Furthermore,the isotropic lattice deformation makes the dielectric function shift and the static dielectric constant change.展开更多
基金supported by the National Key R&D Program of China(Grant No.2020YFA0405700)the Inner Mongolia Science and Technology Major Project(No.2020ZD0011)。
文摘CoCrFeNi high entropy alloy(HEA)has attracted extensive attention due to its excellent corrosion resistance,but the low strength limits its engineering application prospects.In order to develop CoCrFeNi based HEAs with high strength,ductility and corrosion resistance,the effects of Zr content on the microstructure,mechanical properties and corrosion resistance of heterogeneous CoCrFeNiZr_(x)(x=0,0.25,0.5 and 1)HEAs were investigated in this work.The results indicate that the increase of Zr content can significantly affect the phase stability of the alloy,and promote the formation of intermetallic compounds(Ni_(7)Zr_(2)and/or Laves phase)and the transformation of solid solution from face-centered cubic(FCC)structure(x=0,0.25 and 0.5)to body-centered cubic(BCC)structure(x=1).Reasonable control of the Zr content can endow the alloy excellent comprehensive properties.Especially,for CoCrFeNiZr_(0.25) alloy,composed of FCC matrix and a small amount of Ni_(7)Zr_(2)phases,the yield strength(~655 MPa)is increased by nearly four times higher than that of Zr-free alloy,and it also has good ductility(fracture stain>50%).Meanwhile,the corrosion resistance of CoCrFeNiZr_(0.25) alloy is better than that of SS304.The EIS results show that the addition of Zr reduces the stability of the passive film on the alloy,which can be related to the content of the beneficial oxide in the passive film and the thickness of the passive film through XPS analysis.Moreover,the work functions of different phases in CoCrFeNiZr_(x)alloys were obtained by firstprinciples calculations,which further confirmed the selective corrosion mechanism of the CoCrFeNiZr_(x) alloy combining the experimental results.
基金supported by the National Natural Science Foundation of China(60566001,60766002)the Major International Joint Research Program from the Ministry of Science and Technology of China (2008DFA52210)+1 种基金the Project of Guizhou Province Information Industry Department(0831)the Undergraduate Carve Out Project of Bureau of Guiyang Science and Technology(6-5)
文摘A detailed theoretical study on structural,electronic and optical properties of Mg2Si under the isotropic lattice deformation was performed based on the first-principles pseudopotential method.The results show that the isotropic lattice deformation results in a linear decrease in the energy gap for the directΓ15-Γ1 and indirectΓ15-L1 transitions from 93%to 113%,while the indirect band gapΓ15-X1 increases from 93%to 104%and then reduces over 104%.When the crystal lattice is 93%compressed and 113% stretched,the magnesium silicide is a zero-gap semiconductor.Furthermore,the isotropic lattice deformation makes the dielectric function shift and the static dielectric constant change.
