Microstructures and mechanical behavior of NiAl-Mo and NiAl-MoTi two-phase alloys

Journal Article · Thu Dec 01 00:00:00 EST 1994 · Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States)

OSTI ID:6611923

Subramanian, P R; Mendiratta, M G ^[1]; Miracle, D B ^[2]

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1. UES, Inc., Dayton, OH (United States). Materials Research Division
2. Air Force Wright Lab., Wright-Patterson AFB, OH (United States)

The phase relationship in the NiAl-Mo system is characterized by a eutectic equilibrium between binary NiAl and the terminal (Mo) solid solution, thereby offering the potential for development of ductile-phase-toughened composites. A study was conducted to evaluate the effect of varying volume fraction of the (Mo) phase on the microstructure, bend strength, and ambient temperature fracture behavior of selected NiAl-Mo two-phase alloys. Above room temperature, the NiAl-Mo alloys showed an increase in bend strength compared to monolithic NiAl, with reasonable strength retention up to [approximately]800 C. A further enhancement in toughness was realized through hot working. Fractography studies showed evidence for substantial decohesion between the (Mo) phase and the NiAl matrix, thereby suggesting the presence of a weak interface. This weak interface between the (Mo) phase and the NiAl matrix, in conjunction with modulus mismatch stresses, causes the crack to deflect from the (Mo) reinforcement and propagate preferentially along the (Mo)/NiAl interface. These attributes limit the potential for significant ductile-phase toughening in the NiAl-Mo system. An addition of 0.2 at. pct Ti resulted in a marked improvement in the room-temperature fracture toughness of NiAl-Mo. Fractography observations show some evidence for (Mo)/NiAl interface strengthening with the Ti addition.

• OSTI ID: 6611923
• Journal Information: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Vol. 25:12; ISSN 0360-2133
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
MECHANICAL PROPERTIES
MICROSTRUCTURE
MOLYBDENUM
METALLURGICAL EFFECTS
MOLYBDENUM ALLOYS
NICKEL ALLOYS
TITANIUM
COMPARATIVE EVALUATIONS
FRACTURE PROPERTIES
INTERMETALLIC COMPOUNDS
TITANIUM ADDITIONS
ALLOYS
ELEMENTS
EVALUATION
METALS
TITANIUM ALLOYS
TRANSITION ELEMENTS
360102* - Metals & Alloys- Structure & Phase Studies
360103 - Metals & Alloys- Mechanical Properties