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Crack nucleation in hydrogen embrittlement

1992; Pergamon Press; Volume: 27; Issue: 12 Linguagem: Inglês

10.1016/0956-716x(92)90005-y

1873-2712

J.C.M. Li, C.T. Liu,

High Temperature Alloys and Creep

This paper reports on hydrogen embrittlement which is now considered a major factor in the environmental brittleness of intermetallic compounds such as FeAl. For example, when tested in dry oxygen at room temperature, FeAl alloys containing 34-38 atom% Al are ductile (showing grain boundary fracture) with about 18% tensile elongation. In contrast when tested in moist air, the same alloys showed brittle cleavage fracture with less than 4% elongation. But the cause of hydrogen embrittlement is still unknown. The usual concept is that there is some kind of interaction between hydrogen and the crack tip. Several kinds of interactions have been proposed such as decohesion between lattice planes by hydrogen segregation, hydride formation in front of the crack tip, and hydrogen induced dislocation emission which promotes Mode II crack propagation. However, the question of whether hydrogen can help crack nucleation has seldom been addressed.