Chromium addition and environmental embrittlement in Fe[sub 3]Al

Journal Article · Mon Jan 01 00:00:00 EST 1990 · Scripta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-716X(90)90496-4· OSTI ID:6842045

McKamey, C G; Liu, C T ^[1]

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1. Oak Ridge National Lab., TN (United States). Metals and Ceramics Division

Iron aluminides based on Fe[sub 3]Al afford excellent oxidation properties at relatively low cost, making them candidates for use as structural material in corrosive environments. Recently, efforts have been devoted to understanding and improving their ductility through control of grain structure, alloy additions and material processing. Studies at this laboratory have shown that the ambient temperature ductility can be increased significantly by additions of up to 6% Cr. This increase in ductility was earlier attributed to increased cleavage strength, easier cross slip due to lower antiphase boundary (APB) energy, and solid softening. Very recent studies of FeAl and Fe[sub 3]Al in various tensile testing environments have indicated that both alloy systems are relatively more ductile at room temperature when tested in vacuum or dry oxygen. Ductilities of 12--18% were attained in both iron aluminide systems in an oxygen pressure of 6.7 [times] 10[sup 4] Pa, while only 2--4% ductility was achieved in normal laboratory air. It seems appropriate to reexamine the mechanism by which chromium produces improved ductility at room temperature in laboratory air and to correlate it with the environmental effects on mechanical properties. In the current investigation, the authors have evaluated room temperature tensile properties of the binary alloy (Fe-28Al, at.%) and ternary alloy containing chromium (Fe-28Al-4Cr) as a function of surface condition and heat treatment. The results indicate that, although chromium may affect cleavage strength and APB energies, its most significant effect on room temperature ductility is to modify the protective surface oxide, resulting in a minimization of environmental embrittlement.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6842045
• Journal Information: Scripta Metallurgica et Materialia; (United States), Vol. 24:11; ISSN 0956-716X
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
EMBRITTLEMENT
TENSILE PROPERTIES
CHROMIUM
METALLURGICAL EFFECTS
CHROMIUM ALLOYS
IRON BASE ALLOYS
CORROSION PRODUCTS
ELONGATION
EXPERIMENTAL DATA
PROTECTIVE COATINGS
ULTIMATE STRENGTH
YIELD STRENGTH
ALLOYS
COATINGS
DATA
ELEMENTS
INFORMATION
IRON ALLOYS
MECHANICAL PROPERTIES
METALS
NUMERICAL DATA
TRANSITION ELEMENTS
360103* - Metals & Alloys- Mechanical Properties