Low Temperature Hydrogen Embrittlement in Niobium.
ILLINOIS UNIV AT URBANA-CHAMPAIGN DEPT OF METALLURGY AND MINING ENGINEERING
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An experimental study of hydrogen embrittlement in niobium was conducted at temperatures from 115K to 300K in alloys containing from 0.15 to 5.5 at . hydrogen to determine the mechanism of embrittlement. In situ crack propagation studies were made in a scanning electron microscope equipped with a video tape recorder and a tensile cold stage designed for the project. Detailed fractographic studies were made in conjunction with the propagation experiments. Although necking and slip bands testify to extensive plastic deformation in the matrix, fracture surfaces exhibited complete cleavage. All characteristics of the fracture were found to be consistent with the formation of a local, brittle, stress induced niobium hydride phase at the tips of cracks above the stress free solvus temperature. The existence of this phase was confirmed by an electron diffraction structure determination and also by an ion microprobe study.
- Metallurgy and Metallography