Observation of the hydrogen distribution in Ni3Al intermetallic compound

The distribution of hydrogen in Ni3Al intermetallic compounds doped and undoped with boron was investigated by means of tritium TEM autoradiography. The room temperature brittlement of the compound had been explained to be due to the hydrogen embrittlement, and it is well known that a small addition of boron improves the ductility drastically. In the present work, no correlation between the distribution of silver particles, which corresponds to the positions of the trapped tritium, and the grain boundaries was observed, regardless of doping boron or not. The particles were observed nearby the dislocations and grain boundary dislocations. A large amount of particles were observed for the nickel irradiated compound, which contains much voids and dislocations. These results indicate that the static hydrogen trapping sites are not effective for improving the ductility, and support the model in which the mobility of hydrogen through dislocations is retarded by doping boron.