Environmental embrittlement of binary and Zr-doped Ni[sub 3]Al

Conference · Wed Jan 01 00:00:00 EST 1992

OSTI ID:6649396

George, E P; Liu, C T ^[1]; Pope, D P ^[2]

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1. Oak Ridge National Lab., TN (United States)
2. Pennsylvania Univ., Philadelphia, PA (United States). Dept. of Materials Science and Engineering

Single crystals of B-free Ni[sub 3]Al, were cold rolled and recrystallized to produce crack-free polycrystals. Results show that intrinsic ductility ([approximately]16%) of Ni[sub 3]Al (23.4 at. % Al) is considerably higher than previously thought; however, it is severely embrittled by moisture, in air (ductility dropping from a high of [approximately]16% when tested in oxygen to a low of [approximately]3% in air). Since B-doped Ni[sub 3]Al does not show such embrittlement we conclude that a significant part of the beneficial effect of B must be related to suppression of this environmental effect. However, B must also improve grain boundary (GB) cohesion in Ni[sub 3]Al, since our B-free alloy fractures intergranularly whereas B-doped alloys in general fracture transgranularly. Addition of 0.26 at. % of Zr to Ni[sub 3]Al significantly improves its ductility: to 11--13% in air, and 48--51% in oxygen. The ductilities observed in oxygen are comparable to the highest ever ductility observed in B-doped Ni[sub 3]Al, indicating that the GBs in this Zr-doped alloy are not intrinsically brittle (rather, environmental embrittlement is the main reason for its brittleness). Zr dramatically increases the resistance of Ni[sub 3]Al to GB fracture perhaps by increasing GB cohesion. However, Auger analysis shows little or no Zr segregation on the GBs of Ni[sub 3]Al, making it unclear how it might actually affect GB cohesion. Zr does not significantly increase the resistance of Ni[sub 3]Al to environmental embrittlement; nor does it suppress intergranular fracture. In both these respects Zr behaves differently than B.

• Research Organization: Oak Ridge National Lab., TN (United States)
• Sponsoring Organization: USDOE; National Science Foundation (NSF); USDOE, Washington, DC (United States); National Science Foundation, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6649396
• Report Number(s): CONF-921101-98; ON: DE93008575; CNN: DMR/MRL88-19885
• Resource Relation: Conference: 16. Material Research Society international symposium on the scientific basis for nuclear waste management fall meeting, Boston, MA (United States), 30 Nov - 5 Dec 1992
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
EMBRITTLEMENT
FRACTURE PROPERTIES
NICKEL BASE ALLOYS
AIR
BORON ADDITIONS
DOPED MATERIALS
DUCTILITY
GRAIN BOUNDARIES
MOISTURE
OXYGEN
ZIRCONIUM ADDITIONS
ALLOYS
BORON ALLOYS
CRYSTAL STRUCTURE
ELEMENTS
FLUIDS
GASES
MATERIALS
MECHANICAL PROPERTIES
MICROSTRUCTURE
NICKEL ALLOYS
NONMETALS
TENSILE PROPERTIES
ZIRCONIUM ALLOYS
360105* - Metals & Alloys- Corrosion & Erosion
360103 - Metals & Alloys- Mechanical Properties