Design And Preparation Of V-Pd-Mo(Al)alloys For Hydrogen Permeation Research

V-based alloy is a kind of hydrogen permeation materials with distinct characteristics,however,the serious hydrogen embrittlement of V-based alloys is a problem must be solved in its application of hydrogen separation and purification,alloying is a effective method to change the hydrogen solubility and then improve the hydrogen embrittlement resistance of metals.Therefore,according to the typical bcc crystal structure of V metal,the hydrogen repellent elements Pd,Mo and Al were added in V matrix,and 10hydrogenated alloys of V-Pd-Mo?Al?system were designed.The effects of Pd,Mo and Al on the crystal structure,microstructure,hydrogen dissolution,hydrogen diffusion and mechanical properties of V metal were studied,and lattice matching V-Pd-Mo ternary alloy gained in this paper have good hydrogen transmission and hydrogen embrittlement resistance properties.The XRD?BSE and EPMA test results of V?V-3.125Pd(V₆₂Pd₂)and V-6.25Pd(V₆₀Pd₄)alloys show that the Pd element is completely dissolved in V matrix to form bcc-V single phase.Although the doping of Pd dose not produce a new phase structure,the addition of Pd leads to obvious lattice shrinkage of V metal,and the shrinkage is positively related to the content of Pd.Compared with pure V,the ability of dissolving hydrogen of V-Pd binary alloys is significantly reduced,and the resistance to hydrogen embrittlement of V-Pd binary alloys is significantly increased.The hydrogen dissolution enthalpy and room temperature hydrogen diffusion coefficients of the alloys are obtained by isothermal PCT curve test and constant potential step technique.The results show that Mo alloying reduced the hydrogen solubility of V-Pd alloys and improved the hydrogen brittleness,and the lattice matched V-Pd-Mo has a hydrogen diffusion coefficient close to pure V.The effects of Al element with better ductility on the crystal structure and hydrogen transport performance of V-3.125Pd and V-6.25P alloys was studied after that.The results show that the V-1.5625Pd-1.5625Al(V₆₂Pd₁Al₁)and V-3.125Pd-3.125Al(V₆₂Pd₂Al₂)ternary alloys obtained by doping Al element are consist of bcc-V single-phase.The doping of element Al reduces the hydrogen solubility of metal V to a certain extent,thus improving the hydrogen brittleness resistance,but the effect is not as obvious as that of Mo element.In addition,Al alloying has a positive effect on the hydrogen diffusion of V-Pd alloys.Although the effect of Al element on the hydrogen permeability of V-Pd alloy is less obvious than that of Mo element,the ductility of V-Pd-Al alloys is significantly higher than that of V-Pd-Mo alloys.Through a comprehensive comparison,ternary alloy V-3.125Pd-3.125Mo has the lowest hydrogen solubility,the strongest resistance to hydrogen embrittlement,the largest hydrogen diffusion coefficient and better ductility.The design of the alloy in this paper can provide a reference for the research of other hydrolyzed alloy materials.