Speaker
Description
Understanding how hydrogen interacts with individual phases is essential for assessing its effects in multiphase alloys. We combine quantitative thermal desorption spectroscopy with simultaneous neutron diffraction to directly correlate hydrogen release with phase-specific lattice changes. A transportable, neutron-compatible ultrahigh-vacuum setup was applied to hydrogen-charged and uncharged specimens of the γ/γ′ Ni-based superalloy VDM Alloy 780 during isothermal holds between 200 and 500 °C. At 200 and 300 °C, hydrogen induced greater lattice expansion in γ′ than in γ, and hydrogen effusion coincided with contraction of both phases. After 18 h, γ approached the reference lattice parameter, whereas γ′ remained expanded, suggesting slower hydrogen release from γ′. At 300 °C, both phases approached the reference values after 12 h despite approximately 60 wt. ppm residual hydrogen, consistent with retention at deeper traps. These results demonstrate how simultaneous desorption and diffraction measurements connect bulk hydrogen release to the crystallographic response of individual phases, providing insight into hydrogen accommodation and release in precipitation-strengthened alloys.