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

Conference · Wed Jan 01 04:00:00 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: DOE; 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
• Country of Publication: United States
• Language: English

Related Subjects

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