Environmental and strain rate effects on the ductility and yield strength of Fe-40Al

The environmental embrittlement in FeAl is sensitive to strain rate. For instance, the ductility of Fe-45Al has been shown to increase with increasing strain rates. This can be attributed to one of several time-dependent steps in the embrittlement process, involving the dissociation of water to form atomic hydrogen, the diffusion of this hydrogen into the material, etc. The result is that by testing at higher strain rates it is possible to overcome some of the detrimental environmental effects. It is of interest to determine whether the environmental embrittlement can be completely eliminated by a strain rate effect alone. Previous studies on L1{sub 2} intermetallics have revealed different behaviors with regard to this question. For instance, in Ni{sub 3}Al it has been shown that testing at higher strain rates does not fully suppress environmental embrittlement. However, in CO{sub 3}Ti environmental embrittlement can be suppressed at high strain rates. Moreover, for B2-ordered Fe-35Al it has been shown that environmental embrittlement can be suppressed at elevated strain rates. At this time it is unclear why some materials would exhibit this behavior while others would not. Since strain rate effects can provide valuable information as to the nature of environmental embrittlement in intermetallic alloys,more » a study was conducted to investigate the tensile properties of Fe-40Al with regard to both strain rate and test environment. Also, in this study, the alloy was well-annealed to minimize thermal defects prior to tensile testing.« less