Atom probe tomography of deuterium-charged optimised ZIRLO

This study investigates the morphology and composition of hydrides in Optimized ZIRLO following electrochemical deuterium charging. Both ZrO and ZrD_x phases were formed upon charging. The interfaces between these phases are investigated by using atom probe tomography aided by cryogenic sample transfer. The Ga and Sn have formed a “net”-like structure at the original atom probe specimen surface, which is assumed to be associated with the boundaries between individual hydride laths/needles, as it thought to have formed as these species were excluded from the hydrides. Calculation of the D/Zr ratio throughout the sample allows for identification of the ZrD_x phases, revealing the specimen consists of a complex arrangement of different hydride phases. In some areas there is small excess of D in the hydride, i.e. ZrD_2+y. This result is interpreted as deuterium which was “frozen” as it was passing through the hydride during electrochemical charging. The observed microstructural changes and interfacial phenomena contribute valuable insights that may prove useful for improving the performance and safety of Zr alloys.