Diffusion and the dislocation sweeping mechanism for hydrogen transport

A mechanism for H diffusion in metals is proposed. The mechanism for hydrogen transport or sweeping by dislocations has a number of features which invite discussion. A feature which is of some importance is that the pressures calculated in voids due to the sweeping of hydrogen to the voids are not maximum values since ideal gas conditions were assumed. It also reflects a choice of reasonable rather than maximizing values of the parameters. The sweeping mechanism predicts that voids or inclusions can be pressurized by hydrogen, which in turn can account for the much-observed reductions in the ductility of ductile alloys. Similarly, the sweeping of hydrogen to grain boundaries can also result in insidious embrittlement through the loss of cohesion