加工条件对多相V-Ti-Ni合金的显微组织和氢渗透性能的影响

Effect of Processing Conditions on Microstructure and Property of Multiphase V-Ti-Ni Alloys for Hydrogen Purifying

将电弧熔炼V_(55)Ti_(30)Ni_(15)合金在800℃热处理18 h,并在700℃下进行70%压下量的轧制,随后在950℃退火3 h,研究不同加工条件对合金显微组织的影响以及显微组织对合金H渗透率的影响。结果表明,不同加工条件导致的合金显微组织对H渗透率影响很大。热处理后,V基体析出了H渗透率较低的NiTi粒子,减少了作为H渗透主体的V基体体积分数,导致合金H渗透率降低。位错对合金H渗透率有很大影响,轧制后合金含有高密度的位错,极大降低了H渗透率;随后的高温退火工艺则使合金位错密度降低,提高了H渗透率。

The method of separation and purification of hydrogen from a mixed gas based on the permeation of hydrogen through a dense metallic membrane appears as an attractive mean of producing high purity hydrogen at a large scale. V-based alloy membranes with bcc structure are of great interest for hydrogen separation applications due to their low cost and high permeability. The hydrogen flux of the membrane is proportional to its hydrogen permeability and inversely proportional to its thickness. Therefore, V-based alloys should be fabricated in the form of large and thin membranes with the least possible thickness. Rolling process is presently regarded as the most promising route to a large scale fabrication of hydrogen permeable metal membranes. The refractory nature of the most prospective bcc alloys, and their potentially complex compositions, restrict the fabrication techniques which can be applied to form the alloy into a thin foil. In this work, thin sheets of V55Ti30Ni15 alloy were produced by a thermo-mechanical treatment consisting in successive heat treatment, rolling and annealing treatment, and the effect of microstructures resulting from different processing conditions on hydrogen permeability, have been investigated for the multiphase V55Ti30Ni15 alloy. Precipitation of NiTi particles from V-matrix of V55Ti30Ni15 alloy during heat treatment, reduces the volume fraction of V-matrix contributing mainly to hydrogen permeation, which results in the decreasing of hydrogen permeability. The microstructure of the alloy after heat treatment evolved into a fibrous/lamellar microstructure during hot-rolling deformation, and a significant reduction in hydrogen permeability accompanied this deformation. Subsequent annealing decreased the dislocation density and increased hydrogen permeability. Dislocations have a great impact on hydrogen permeability due to their ability to trap diffusing hydrogen.