Processing and mechanical properties of NiAl-based in-situ composites. Ph. D. Thesis Final report

Technical Report · Sun May 01 04:00:00 EDT 1994

OSTI ID:7072152

Johnson, D R

In-situ composites based on the NiAl-Cr eutectic system were successfully produced by containerless processing and evaluated. The NiAl-Cr alloys had a fibrous microstructure while the NiAl-(Cr,Mo) alloys containing 1 at. percent or more molybdenum exhibited a lamellar structure. The NiAl-28Cr-6Mo eutectic displays promising high temperature strength while still maintaining a reasonable room temperature fracture toughness when compared to other NiAl-based materials. The Laves phase NiAlTa was used to strengthen NiAl and very promising creep strengths were found for the directionally solidified NiAl-NiAlTa eutectic. The eutectic composition was found to be near NiAl-15.5Ta (at. percent) and well aligned microstructures were produced at this composition. An off-eutectic composition of NiAl-14.5Ta was also processed, consisting of NiAl dendrites surrounded by aligned eutectic regions. The room temperature toughness of these two phase alloys was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa. Polyphase in-situ composites were generated by directional solidification of ternary eutectics. The systems investigated were the Ni-Al-Ta-X (X=Cr, Mo, or V) alloys. Ternary eutectics were found in each of these systems and both the eutectic composition and temperature were determined. Of these ternary eutectics, the one in the NiAl-Ta-Cr system was found to be the most promising. The fracture toughness of the NiAl-(Cr,Al)NiTa-Cr eutectic was intermediate between those of the NiAl-NiAlTa eutectic and the NiAl-Cr eutectic. The creep strength of this ternary eutectic was similar to or greater than that of the NiAl-Cr eutectic.

• Research Organization: Tennessee Univ., Knoxville, TN (United States)
• OSTI ID: 7072152
• Report Number(s): N-94-36954; NASA-CR--195333; E--8864; NAS--1.26:195333; CNN: NAG3-876; RTOP 505-63-52
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360601 -- Other Materials-- Preparation & Manufacture
360602 -- Other Materials-- Structure & Phase Studies
360603* -- Materials-- Properties
ALLOYS
ALUMINIUM ALLOYS
CHROMIUM
COMPOSITE MATERIALS
ELEMENTS
EUTECTICS
FRACTURE PROPERTIES
MATERIALS
MECHANICAL PROPERTIES
METALS
MICROSTRUCTURE
MOLYBDENUM
NICKEL ALLOYS
SYNTHESIS
TANTALUM
TRANSITION ELEMENTS
VANADIUM