Susceptibility of B2-ordered iron aluminides to moisture-induced embrittlement in oxygen and argon environments

Abstract

Room-temperature ductility of iron aluminides is very sensitive to moisture in the testing environment. In a previous study, elongations in air were found to increase with decreasing relative humidity. The most substantial ductility changes occurred at low humidity levels, suggesting that only a small amount of water vapor is needed to embrittle the material. In order to gain a better understanding of the interaction of these materials with water vapor, alloys were tested in environments containing substantially lower water contents. A dew-point device was employed to measure water contents down to several parts per million by volume (vpm). Tensile tests were conducted in argon and oxygen environments. These environments were chosen to investigate an apparent beneficial effect of oxygen on ductility. Previous studies have observed higher elongations in oxygen than in other environments, including vacuum. This effect was not observed in the work of Gaydosh and Nathal; however, the oxygen employed in their testing contained relatively large amounts of water vapor.