Ni-enrichment and its influence of the structure, chemistry, and bonding of grain boundaries in Ni{sub 3}Al

Book · Tue Aug 01 04:00:00 EDT 1995

OSTI ID:78342

Subramanian, S; Muller, D A; Silcox, J; Sass, S L ^[1]

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1. Cornell Univ., Ithaca, NY (United States)

Small angle [001] twist boundaries and [001](110) tilt boundaries in B-free and B-doped Ni-rich Ni{sub 3}Al (76 at. pct. Ni) were examined using conventional electron microscopy techniques as well as annular dark field (ADF) imaging, X-ray Fluorescence (XRF) and spatially resolved electron energy loss spectroscopy (EELS) in an UHV scanning transmission electron microscope. The interface Structure consists of periodically spaced pairs of a/2{l_angle}110{r_angle} partial dislocations, linked by an antiphase boundary (APB). An analysis of the separation of the partials gives APB energies which are lower than in bulk Ni{sub 3}Al and which decrease with increasing misorientation angle. EELS, XRF and ADF imaging demonstrate that the APBs are Ni-rich. The observations on the APB chemistry and energy taken together lead to the conclusion that Ni-enrichment occurs to lower boundary energy by decreasing the number of high energy Al-Al bonds across the APB. These results on small angle boundaries lead to the suggestion that Ni-enrichment also occurs at large angle boundaries to decrease the number of high energy bonds across the interface.

• DOE Contract Number: FG02-85ER45211; FG02-87ER45322
• OSTI ID: 78342
• Report Number(s): CONF-941144--; ISBN 1-55899-265-0
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
BORON ADDITIONS
BURGERS VECTOR
CHEMICAL BONDS
DISLOCATIONS
EXPERIMENTAL DATA
GRAIN BOUNDARIES
INTERMETALLIC COMPOUNDS
NICKEL BASE ALLOYS
SEGREGATION