Environmental effects in iron aluminides |
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Authors: | R Balasubramaniam |
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Affiliation: | (1) Department of Materials and Metallurgical Engineering, Indian Institute of Technology, 208 016 Kanpur, India |
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Abstract: | Iron aluminides based on the stoichiometric compositions of Fe3Al and FeAl exhibit poor room temperature ductilities due to hydrogen embrittlement (HE). The presence of surface passive
films reduces HE. The reduction is due to the lower rate of hydrogen liberation on the surface of iron aluminides with a passive
layer. Theoretical and experimental verification for this idea are provided. The effect of addition of passivity-inducing
elements Ti, Zr, V, Nb, Ta, Cr, Mo, W, Si and Ni to Fe3Al on the thermomechanical and electrochemical behaviour has been outlined. The Cr- and Ti-alloyed intermetallics exhibited
significant room temperature ductilities. Microstructural studies of the alloyed intermetallics revealed that when the addition
of passivity-inducing element results in the precipitation of brittle phases with Fe and Al, they crack during the processing
operation. The addition of oxygen-active elements on the embrittlement behaviour is also discussed. The effect of these additions
on the potentiodynamic polarization behaviour and high temperature oxidation behaviour is also briefly addressed. Methods
to minimize HE by the addition of elements that irreversibly trap hydrogen and that prevent recrystallization have also been
discussed. |
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Keywords: | Iron aluminides passivity hydrogen embrittlement structure-property-processing correlation |
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