Comments on optimization of the boron content in FeAl (40 at. % Al) alloys
- Dartmouth College, Hanover, NH (United States). Thayer School of Engineering
In a recent paper, Webb, Juliet and Lefort indicated, based on tensile tests of two boron-doped FeAl alloys and one undoped FeAl alloy, that they had determined the optimum concentration of boron for good ductility to be 48 appm (12 wppm) in Fe-40Al (compositions given in atomic percent throughout). It is the author's view that this is not the case for the following reasons: (1) The Fe-40Al alloys studied by Webb et al. contained 42:4, (heat [number sign]1), 45.7 (heat [number sign]2) and 39.7 (heat [number sign]3) atomic percent Al. (2) The maximum solubility of an element may depend on the presence of other elements. (3) Other workers, notably Liu and George have obtained greater elongations in Fe-40Al in air (4.3%) than the 2.5% obtained by Webb et al. with a greater boron concentration (300 wppm as opposed to 12 wppm). Similarly, Crimp et al. found little difference in the tensile behavior of slow-cooled Fe-40Al with boron levels in the range 500 to 2000 wppm, with a ductility at 3% elongation that was comparable to the highest obtained by Webb et al. (4) Boron in FeAl presumably partitions between the lattice and the grain boundaries. (5) The grain size in the boron-free alloys studied by Webb et al. was larger at 54 [mu]m than in the boron-doped alloys (37 [mu]m and 27 [mu]m for the alloys containing 12 and 80 wppm B, respectively). (6) When tensile tests are performed on FeAl in air, the ductility is reduced due to water vapor. To some extent boron may ameliorate this environmental effect. Thus, differences in ductility in air are not necessarily due to intrinsic behavior but may be due to a reduced environmental effect in boron-doped alloys. (7) Webb et al. conducted their tensile tests at a strain rate of 3 x 10[sup [minus]2]s[sup [minus]1].
- DOE Contract Number:
- FG02-87ER45311
- OSTI ID:
- 5989119
- Journal Information:
- Scripta Metallurgica et Materialia; (United States), Vol. 29:6; ISSN 0956-716X
- Country of Publication:
- United States
- Language:
- English
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