Interaction of H2O and O2 with Ni3Fe and their effects on ductility

Possible reasons for the high ductility of Ni3Fe and its insensitivity toward the testing environment have been investigated. Thermal desorption experiments have shown that water dissociates on clean Ni3Fe surfaces to produce atomic hydrogen. Ductility measurements of cast and cold-rolled polycrystalline Ni3Fe demonstrated that the reduced ductility was obtained only when the testing was performed with oxygen carefully removed. X-ray photoemission studies indicate that oxygen interacts with water to form hydroxyls, thereby suppressing the production of atomic hydrogen. Hydrogen desorption from the Ni3Fe surface requires a lower activation energy, resulting in a smaller surface hydrogen concentration at a given temperature. Hence it is possible that there is insufficient hydrogen to cause the nucleation and growth of brittle cracks for severe embrittlement.