高い固溶水素濃度状態における純ニオブ水素透過膜の変形と破壊の形態

Abstract

The deformation and fracture modes of pure niobium metal membrane were investigated by a series of hydrogen permeation tests in a highly soluble hydrogen state. The membrane underwent a large plastic deformation due to the lattice expansion and contraction during hydrogenation and dehydrogenation. A crack initiated on the membrane surface under the tensile stress condition, but not under the compressive stress condition. All the fractured sections in the membrane showed the characteristics of quasi-cleavage fracture. However, even in the case of a large amount of hydrogen dissolved into the membrane, it never fractured as far as hydrogen keeps permeating through the membrane at a constant temperature and a constant hydrogen pressure difference between inlet and outlet surfaces. In other words, brittle fracture of pure niobium metal membrane was not caused by the amount of dissolved hydrogen, but by either a rapid change in the hydrogen density in the membrane or a continuous hydrogen dissolution reaction in progress into it.