Local electronic structure and cohesion of grain boundaries in Ni{sub 3}Al
- Cornell Univ., Ithaca, NY (United States)
- IBM Thomas J. Watson Research Center, Yorktown Heights, NY (United States)
One of the fundamental questions concerning Ni{sub 3}Al is why doping with boron improves the room temperature ductility of the polycrystalline material. Boron is thought to prevent environmental embrittlement and increase the cohesive strength of grain boundaries since it changes the fracture mode from intergranular to transgranular. This change in cohesive energy must be reflected in the bonding changes at the grain boundary which can be probed using spatially resolved electron energy loss spectroscopy (EELS). The authors have examined grain boundaries in both undoped and boron doped Ni{sub 0.76}Al{sub 0.24} using EELS, EDX and ADF imaging in a UHV STEM.Ni-enrichment is seen in a 0.5--1 nm wide region at large angle grain boundaries, both in the absence and presence of B. EELS shows that B segregation can vary along the interface. The Ni L{sub 2,3} core edge fine structure which is sensitive to the filling of the Ni d-band, shows only the boron rich regions of the grain boundary to have a bonding similar to that of the bulk material. These results demonstrate that boron segregation increases the cohesive energy and hence improves the fracture resistance of the grain boundary, by making the bonding at boundaries similar to that in the bulk. The measured changes in d band filling may also affect the local solubility of hydrogen.
- DOE Contract Number:
- FG02-85ER45211; FG02-87ER45322
- OSTI ID:
- 72470
- Report Number(s):
- CONF-941144-; ISBN 1-55899-265-0; TRN: IM9530%%82
- Resource Relation:
- Conference: Fall meeting of the Materials Research Society (MRS), Boston, MA (United States), 28 Nov - 9 Dec 1994; Other Information: PBD: 1995; Related Information: Is Part Of High-temperature ordered intermetallic alloys VI: Part 2. Materials Research Society symposium proceedings Volume 364; Horton, J. [ed.] [Oak Ridge National Lab., Oak Ridge, TN (United States)]; Baker, I. [ed.] [Dartmouth College, Hanover, NH (United States)]; Hanada, Shuji [ed.] [Tohoku Univ., Sendai (Japan)]; Noebe, R.D. [ed.] [NASA Lewis Research Center, Cleveland, OH (United States)]; Schwartz, D.S. [ed.] [McDonnell Douglas Aerospace, St. Louis, MO (United States)]; PB: 760 p.
- Country of Publication:
- United States
- Language:
- English
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