HYDROGEN TRANSPORT THROUGH ANNEALED AND DEFORMED ARMCO IRON

The diffusivity and solubility of hydrogen in ferrous materials near 300K are of substantial interest with respect to hydrogen brittleness. The characteristic disappearance of hydrogen brittleness at lower temperatures and high strain rates implies that hydrogen transport is an essential step in the brittleness mechanism. In the work reported, a sensitive electrochemical permeation technique was used to study hydrogen trapping in annealed and plastically deformed iron. The thermal stability of the trap structure was also investigated. Two types of hydrogen traps were indicated by transient measurements on membranes with different processing histories. Both are caused by deformation; only one of them could be removed by annealing. It is stated that these traps are not readily explained in terms of the stress field of a single dislocation and are probably associated with some feature of the dislocation cell structure caused by deformation.