The hydrogen solubility and diffusivity in nickel aluminide and developing a hydrogen tolerant nickel aluminide alloy

[摘要] The solubility of H in single crystals and polycrystalline samples of $m Nisb{3}Al$ has been measured in equilibrium with $m Hsb2$ gas at atmosphere. In all cases the solubility exhibits a maximum at 750 K. A structural transformation from $m Llsb2$ (cubic) to $m Llsb2$ (tetragonal) in hydrogenated $m Nisb3Al (Nisb3Al$-H) was observed. The transformation temperature was found to be between 720 K and 870 K. No enthalpy change during this transformation was detected in the DTA experiment.The diffusivity of hydrogen in $m Nisb3Al$ has been measured in the temperature range of 588 K to 1214 K using a method involving the outgassing of hydrogen charged spheres. The diffusivity of hydrogen exhibits discontinuity in the temperature range of 753 K to 793 K.Finally, the addition of Pd (0.5 wt) is shown to significantly suppress the hydrogen embrittlement of $m Nisb3Al.$ Microstructure analysis indicates no second phase is formed due to the small amount of Pd. The addition of Pd alters the fractography of $m Nisb3Al$ charged with hydrogen. It is suggested that Pd may play a role of trapping hydrogen atoms in lattice and result in reducing the hydrogen concentration around crack tips and grain boundaries, thus improving the susceptibility of $m Nisb3Al$ to hydrogen embrittlement.

[发布机构] Rice University

[效力级别] Materials