Zr-Nb-Mn alloys were developed to investigate hydrogen diffusion and its effects among different manganese additions. Thermo-Calc® and TC-Prisma simulations were used to determine the studied chemical compositions and to estimate the volume fraction and the mean radius of precipitates. Three compositions were chosen to be melted and thermomechanically processed, resulting in an α-Zr matrix with fine β-Nb precipitation. TDS results indicated that hydrogen diffusion coefficient was 10-12 m2.s-1 for all the analyzed compositions. The manganese addition increased the strength while ductility was maintained. Although optical microscopy revealed that the increase of manganese content resulted in less oriented hydrides, the reduction in ductility was similar for the three studied compositions. Results showed manganese as a promising addition element for zirconium alloys due to the increase of hydrogen solubility, the good relationship between strength and ductility and the morphology of the hydrides.

The purpose of this study was to investigate the kinetics of hydrogen absorption and hydride formation and their effect on the mechanical properties in Zr-1Nb and Zr-1Nb-1Sn-0.1Fe alloys, which were thermomechanically processed and gaseously hydrided at 320ºC under 10 bar hydrogen pressure. X-ray diffraction (XRD) confirmed the formation of α-Zr matrix after final heat treatment. The alloys absorbed almost the same amount of hydrogen, although with different kinetics. Absorption began almost immediately in Zr-1Nb alloy whilst in Zr-1Nb-1Sn-0.1Fe hydrogen absorption started after 11 h besides a faster hydrogen kinetics. Results showed that tensile strengths for both alloys were nearly independent of absorbed hydrogen. Fractographic examinations indicated ductile fractures for unhydrided condition whereas quasi-cleavage features were observed for all hydrided specimens.

Samples of amorphous and partially crystallized Fe40Ni38Mo4B18 alloy were submitted to hydrogen gas permeation from 523 to 643 K. The hydrogen permeation curves exhibited a single sigmoidal shape, typical of tests where no hydride formation occurs. It was observed that the hydrogen diffusivity increases for the amorphous samples and partially crystallized alloy with the temperature increase. The hydrogen diffusion coefficient as a function of temperature was found to be D = 5.1 ± 0.5 × 10-12 exp (-11.0 ± 3.5/RT) (m².s-1) for amorphous condition and D = 3.6 ± 0.5 × 10-11 exp (-19.8 ± 3.3/RT) (m².s-1) for the partially crystallized condition. This suggests that the annihilation of defects in the amorphous structure and the crystalline phase precipitate contributes to the increase of the hydrogen diffusion.