Microstructures and properties of two-phase nickel-aluminides and an investigation of the role of boron inductilizing Ni sub 3 Al

Thesis/Dissertation · Fri Jan 01 00:00:00 EST 1988

OSTI ID:5251096

Khadkikar, P S

Several Ni-Al alloys with aluminum contents varying from 24 to 45 at% were prepared by hot extrusion of prealloyed Ni{sub 3}Al and NiAl powders. Fully recrystallized and fine-grain microstructures were obtained via powder metallurgy route. The Ni{sub 3}Al plus boron alloys (24 at% aluminum) produced by power metallurgy technique exhibited room-temperature tensile elongations up to 50%, however, these alloys were found to be brittle in elevated-temperature tests conducted in air. Notched-specimen tensile tests performed on Ni{sub 3}Al and Ni{sub 3}Al+B did not indicate significant improvement in the grain-boundary adhesive strength due to boron. A critical stress was observed to be necessary for fracture initiation that occurred in a brittle intergranular fashion in the presence of a constraint (notch). The yield strengths of both Ni{sub 3}Al and Ni{sub 3}Al+B exhibited Hall-Ptech behavior at room temperature. It was concluded, based on the results of the notched tensile tests and Hall-Petch behavior, that boron improves the room-temperature tensile ductility by diffusing the stress concentration at the grain boundaries rather than by improving the grain-boundary adhesive strength.

• Research Organization: Case Western Reserve Univ., Cleveland, OH (USA)
• OSTI ID: 5251096
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
DUCTILITY
BORON ADDITIONS
METALLURGICAL EFFECTS
NICKEL ALLOYS
GRAIN BOUNDARIES
MICROSTRUCTURE
TENSILE PROPERTIES
ALLOYS
BORON ALLOYS
CRYSTAL STRUCTURE
MECHANICAL PROPERTIES
360102* - Metals & Alloys- Structure & Phase Studies
360103 - Metals & Alloys- Mechanical Properties