Email RIS file
Bookmark
Report an Issue

Role of boron additions on grain-boundary chemistry and tensile properties of Ni3Al containing 24 and 26 at. % Al.

Author
Liu, C. T.
Published
United States : [publisher not identified], 1984
Springfield, Va.: National Technical Information Service, [approximately 1984]
Physical Description
microfiche : negative ; 11 x 15 cm
Additional Creators
Horton, J. A. and White, C. L.

Availability

Browse Nearby on Shelf
I Want It
I Want It

Finding items...

Summary
Effects of up to 0.4 wt % B in Ni3Al containing 24 to 26 at. % Al were studied. Room-temperature ductility and fracture behavior of B-doped Ni3Al depend critically on deviation from alloy stoichiometry. As the Al content of B-doped Ni3Al is decreased below 25 at. %, the ductility increases dramatically and the fracture mode changes from intergranular to transgranular. Auger studies indicate that the intensity of boron segregated to grain boundaries increases and the concentration of grain-boundary Al decreases significantly with decreasing bulk Al concentration. These results suggest that alloy stoichiometry strongly influences grain-boundary chemistry, which, in turn, affects the grain-boundary cohesion. Boron exhibits an unusual segregation behavior in Ni3Al, i.e., it has a strong tendency to segregate to the grain boundaries but not to cavity (free) surfaces. On the other hand, sulfur, an embrittling impurity, tends to segregate more strongly to free surfaces than to grain boundaries. The beneficial effect of boron is in agreement with existing theories of solute segregation effects on grain-boundary cohesion. The yield stress of B-doped Ni3Al decreases with increasing grain size produced by long-term annealing at 1000/sup 0/C. The yield stress obeys the Hall-Petch relation: sigma/sub y/ = sigma/sub o,y/ + k/sub y/ d/sup -1/2/ with sigma/sub o,y/ = 163 MPa and k/sub y/ = 8.2 MPa cm/sup 1/2/. The tensile elongation was initially independent of grain size, and showed only a moderate decrease from about 50 to 40% with grain diameters larger than 110 ..mu..m.
Report Numbers
DE85001264; CONF-8409142-1
Other Subject(s)
Collection
NTIS collection.
Note
DOE contract number: AC05-84OR21400
OSTI Identifier 6510913
Research organization: Oak Ridge National Lab., TN (USA).
View MARC record | catkey: 47346458