| Abstract Scope |
Atom probe tomography is a powerful technique for the characterisation of materials. It provides beautiful 3D datasets that show the precise position and species of atoms within a needle shaped volume with a tip radius of ~100 nm. However, until recently, hydrogen in the atom chamber meant that it could not be used to accurately measure hydrogen. By using a custom-designed cryogenic transfer set-up, we have been able to obtain world-first 3D maps that show the distribution of hydrogen around the common microstructural features in steels. This work includes the first ever observations of hydrogen at dislocations, finally providing a concrete validation of the theory of hydrogen-enhanced dislocation mobility as a mechanism of hydrogen embrittlement. It also provides the first direct observations of hydrogen at the interface between incoherent precipitates and the surrounding steel matrix, settling a long-standing debate around whether hydrogen trapping is an interfacial effect (it is). |