Environmental embrittlement of binary and Zr-doped Ni{sub 3}Al
Conference
·
OSTI ID:10136656
- Oak Ridge National Lab., TN (United States)
- 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, Washington, DC (United States); National Science Foundation, Washington, DC (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 10136656
- Report Number(s):
- CONF-921101--98; ON: DE93008575; CNN: Grant DMR/MRL88-19885
- Country of Publication:
- United States
- Language:
- English
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