The effect of strain rate on the room-temperature ductility of FeAl

Journal Article · Fri Nov 01 04:00:00 EST 1991 · Scripta Metallurgica; (United States)

DOI:https://doi.org/10.1016/0956-716X(91)90071-8· OSTI ID:5722954

Nagpal, P ^[1]; Baker, I ^[2]

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1. Illinois Inst. of Tech., Chicago, IL (United States). Dept. of Mechanical and Aerospace Engineering
2. Dartmouth Coll., Hanover, NH (United States). Thayer School of Engineering

Recently it has been shown that the ductility of iron-rich FeAl depends on extrinsic factors such as the test environment and the heat treatment. The environmental effect was first demonstrated for Fe-36.5 at.% Al which exhibited a higher elongation (5.4%) when tested in vacuum than when tested in air (2.2%). Similarly, Fe-40 at.% Al showed higher ductility ({approximately}5%) in vacuum in comparison with tests performed in air ({approximately}1%). It has also been shown that the cooling rate after annealing can have a dramatic effect on ductility. It was demonstrated that air-cooled samples of FeAl, with aluminum contents from 34 to 50 at.%, were more brittle than similar samples which were more slowly cooled. The lower ductility presumably arose from hardening by quenched-in vacancies, and it was shown that a low temperature anneal (400{degrees} C) could remove this hardening effect. It was demonstrated that after this low temperature anneal Fe-45 at.% Al could exhibit {approximately}3% elongation when tested in air, whereas without this anneal failure before yield occurs in tension for aluminum contents above 40 at.%. It appears that the cooling rate effect is additive to effect of the test environment. For example, Fe-40 at.% Al when furnace-cooled and tested in vacuum exhibited {approximately}9% elongation. In this paper it is suggested that the embrittlement of FeAl is due to the atomic hydrogen arising from a reaction between water vapor and aluminum atoms, which produces Al{sub 2}O{sub 3}. The hydrogen atoms diffuse to the crack tip, see reference 8, and this reduces the stress to fracture. Since the hydrogen diffusion is time-dependent, presumably there will be a strain-rate dependence of the ductility. The present study was thus performed to examine the effect of strain rate on the ductility of Fe-45 at.% Al.

• OSTI ID: 5722954
• Journal Information: Scripta Metallurgica; (United States), Journal Name: Scripta Metallurgica; (United States) Vol. 25:11; ISSN 0036-9748; ISSN SCRMB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
AIR
ALLOYS
ALUMINIUM
ALUMINIUM ALLOYS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
BRITTLENESS
CHALCOGENIDES
CHEMICAL REACTIONS
COOLING
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DUCTILITY
ELEMENTS
FLUIDS
GASES
HEAT TREATMENTS
HYDROGEN
IRON ALLOYS
MECHANICAL PROPERTIES
METALS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
POINT DEFECTS
QUENCHING
STRAINS
TEMPERATURE RANGE
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
TENSILE PROPERTIES
VACANCIES
VAPORS
WATER VAPOR