The hydrogen embrittlement of metals

This paper represents a comprehensive survey of the literature with regard to the subject of hydrogen embrittlement in metals. There is a review of the current knowledge of hydrogen-metal relationships in which it is shown that the behaviour of any element, with respect to hydrogen, depends upon its position in the periodic table. The current theories of the nature of brittle fracture, and of the ductile-to-brittle transition in metals are then reviewed in terms of the origin and propagation of brittle fractures on the application of an external stress. These reviews are then followed by a detailed critical analysis of the characteristics and mechanisms of hydrogen embrittlement in the body-centered-cubic metals (including steel), titanium and its alloys, alphazirconium and alpha-uranium. In each case these effects are discussed in terms of the present knowledge of the appropriate metal-hydrogen system and the theory of brittle fracture in metals. The conclusions from each of these individual reviews are then combined in the proposal of a general theory of the hydrogen embrittlement of metals which not only incorporates the essential features of each case of hydrogen embrittlement, but also suggests an explanation for the absence of similar effects in other metals.