Microstructure And Hydrogen Transport Properties Of V-Ni-M Hydrogen Filtration Alloy

V-based hydrogen filtration alloys have received extensive attention due to their excellent hydrogen transport properties.Among them,V85Ni15 alloy has excellent hydrogen embrittlement,but its hydrogen permeation rate is low,and its hydrogen permeation coefficient is 2.17×10-8 mol H2 m-1s-1Pa-0.5 at 673 K temperature.Therefore,based on the matching of the alloy hydrogen permeation flux and hydrogen embrittlement resistance,this paper selects V85Ni15 as the comparative alloy,adds Al,Co,Cr,Cu and Fe into the alloy to design a hydrogen filtration alloy with a total of 10 components in the V-Ni-M system(A: V85M15 and B: V₈₅Ni₁₀M₅).The effects of alloying elements on the microstructure and hydrogen dissolution,diffusion,permeability and other transport properties of V-Ni-M alloys were investigated.The results of XRD and SEM test of V-Ni-M alloy show that all alloys are singlephase solid solution structures in bcc-V phase,and Al,Co,Cr,Cu,Fe and Ni are solid dissolved in the bcc-V phase.From the two aspects of atomic radius and electronic structure,the addition of these alloying elements will cause the lattice of bcc-V to be compressed,and the diffraction peak will shift to the right than the ratio of pure V.The diffraction peak of A1# alloy V85（Co Cr Fe Ni）15 and A6# alloy V85（Al0.5Co Cr Cu Fe Ni）15 in group A is closest to V85Ni15,and the diffraction peak of A4# alloy V85（Al Co CrCu Ni）15 is closest to pure V.The hydrogen permeation experiments of various alloys show that the hydrogen permeation properties of all alloys can be improved by replacing Al with Co,Cr,Cu and Fe.Hydrogen permeation coefficients of V85（Co Cr Fe Ni）15,V85（Al Co Cr Fe Ni）15,V85（Al Co Cr Cu Ni）15,V85（Al0.5Co Cr Cu Fe Ni）15,V85Ni10（Co Cr Fe）5 Alloy under 673 K are 2.91,2.27,4.42,3.92 and 2.41 mol H2 m-1s-1Pa-0.5.From the analysis of the hydrogen embrittlement of the alloy,the hydrogen brittleness of the alloy is slightly worse than that of the alloy V85Ni15.However,under the temperature of hydrogen filtration（523K-673K）,both V85（Co Cr Fe Ni）15 and V85（Al0.5Co Cr Cu Fe Ni）15 exhibit good hydrogen permeability and hydrogen embrittlement resistance.The hydrogen absorption PCT curves of the alloys show that the amount of hydrogen dissolved in the alloy decreases with the increase of the experimental temperature,and increases with the enhancement of hydrogen pressure.When the hydrogen pressure is low,the rate of hydrogen dissolution is faster,which is in line with the Siverts formula.By fitting the PCT curve,the order of the hydrogen dissolution coefficient of each alloy is as follows: V85（Al0.5Co Cr Cu Fe Ni）15>V85（Al Co Cr Fe Ni）15 >V85（Co Cr Fe Ni）15>V85Ni10（Co Cr Fe）5>V85Ni15.With the in-crease of Ni content,the hydrogen dissolution coefficient of the alloys gradually decreases,indicating that Ni has a strong hydrophobic ability and the addition of Al increases the hydrogen solubility coefficient of the alloys,indicating that the hydrogen hydrophobic capacity of the Al is weaker.The hydrogen dissolution coefficient of V85（Al0.5Co Cr Cu Fe Ni）15 alloy is the largest,which is 1.77 times of V85Ni15 at 673 K.The hydrogen transfer behavior of the alloys was analyzed from the perspective of hydrogenation potential.The migration rate of H atom,intrinsic diffusion coefficient and diffusion activation energy of hydrogen were obtained by fitting analysis.It is found that with the increase of temperature,the greater the migration rate of hydrogen atoms,the greater the intrinsic diffusion coefficient of the corresponding alloys.The order of intrinsic diffusion coefficients of each alloy is as follows: V85（Al0.5Co Cr Cu Fe Ni）15> V85Ni15> V85（Co Cr Fe Ni）15> V85（Al Co Cr Fe Ni）15> V85Ni10（Co Cr Fe）5.The order of diffusion coefficient is the same as that of the alloy XRD diffraction peak.The closer the diffraction peak is to pure V,the greater the intrinsic hydrogen diffusion coefficient of the alloy.Based on the data analysis of hydrogen dissolution,hydrogen diffusion,hydrogen permeability and hydrogen brittleness resistance of ten alloys components,the V85（Co Cr Fe Ni）15 and V85（Al0.5Co Cr Cu Fe Ni）15 alloys have better hydrogen transfer performance under experimental conditions than V85Ni15 alloy.The hydrogen permeation fluxes of V85（Co Cr Fe Ni）15 and V85（Al0.5Co Cr Cu Fe Ni）15 alloys are 1.34 and 1.81 times of the comparative alloy V85Ni15 at 673 K,respectively,and exhibit good hydrogen embrittlement resistance.