| Hydrogen energy is a kind of renewable clean energy,and recently has become the focus of energy strategy of countries around the world.Hydrogen gas produced in industrial hydrogen production(such as fossil energy reforming hydrogen production)contains many by-products,such as H2S,N2,CO,and CO2.Therefore,"hydrogen separation technology"has become an important technical link for obtaining pure hydrogen.At present,although Pd-based membranes have been commercially used for hydrogen separation,Pd is a rare resource and expensive,thus it is urgent to develop new metal membrane materials that have both low cost and high hydrogen permeability.Based on the above background,group 5B metals(Nb,V,and Ta),which have higher hydrogen permeability and are relatively inexpensive,have received important attention and research.The literatures show that the Nb-Ti-Fe hydrogen separation alloy is very promising as a metal membrane material to replace Pd base alloys.However,so far due to the lack of a complete phase diagram of this alloy and the lack of high-temperature equilibrium phase data.The positioncomposed of the dual-phase structure in the phase diagram,i.e.the"hydrogen permeation component region"is still unclear.In addition,it is unknown whether there are alloys with higher hydrogen permeability in the hydrogen permeation region,thus it is urgent to conduct in-depth research.Based on this,this article uses the Nb-Ti-Fe alloy system as the research object,starting from the Calculation of Phase Diagram(CALPHAD)and experimental analysis.The phase diagram,microstructure,hydrogen transport behavior and mechanical properties of Nb-Ti-Fe alloy have been studied in detail.The details are as follows:1.The Nb-rich angle phase diagram of Nb-Ti-Fe alloy has been researched,which clarified the key information of solidification path,type and number of phase regions,alloy solidification equilibrium reaction and sequence of precipitated phases.Based on this,the microstructure and solidification rules of the 17 alloy components of the Ti Fe phase region and nearby locations in the phase diagram were verified and analyzed by experiments,and more accurately position the"hydrogen permeation component region"in the phase diagram.2.Based on the above research,the relationship between the microstructure and the hydrogen permeability of different alloys in the"hydrogen permeation component region",that is,the Ti Fe phase region,and the hydrogen permeation mechanism have been studied.The results show that the alloys with primary Ti Fe phase and the eutectic{Bcc-(Nb,Ti)+Ti Fe}dual-phase structure perform excellent hydrogen permeability and hydrogen embrittlement resistance,and the content and morphology of the eutectic structure have a greater impact on the hydrogen permeation performance.Among them,Nb5Ti60Fe35alloy has the highest hydrogen permeability of 3.82×10-8(mol H2m-1s-1Pa-1/2),at 673 K.The hydrogen permeation mechanism of these alloys can be explained by a two-phase mixing model.3.The effects of different Ti/Fe ratios and Nb content on the microstructure,phase volume fraction and hydrogen transport properties of Nb-Ti-Fe alloys were studied,and the relationship between alloy composition,microstructure,phase volume fraction and hydrogen transport properties was clarified.In addition,the microhardness and hydrogenation properties of alloys with different compositions were tested and analyzed,and the comprehensive properties of Nb-Ti-Fe alloys were analyzed from the mechanical and hydrogen absorption properties of the alloys. |
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