Effect of temperature on hydrogen environment embrittlement of niobium

Tensile properties of Nb were investigated in 1.1 MPa hydrogen and argon in the temperature range of 473 similar to 1273 K. The effect of temperature on hydrogen environment embrittlement (HEE) of the material was also examin ed. The results obtained are as follows: HEE occurred at the temperature range of 673 similar to 1073 K and showed m aximum at 800 K. In this temperature range, hydrogen decreased elongation a nd ultimate tensile strength of the material with decreasing the strain rat e. Cleavage fracture together with the striations was observed on the fract ure surface in hydrogen, while ductile rupture was observed in argon. No hy dride was observed in the specimen fractured in hydrogen by X-ray diffracti on. It is discussed that HEE of Nb occurred at this temperature range by th e similar mechanism of HEE of iron without hydride near room temperature.