Microstructures and mechanical properties of NiAl-Ni sub 2 AlHf alloys

Journal Article · Fri Jun 01 00:00:00 EDT 1990 · Journal of Materials Research; (USA)

DOI:https://doi.org/10.1557/JMR.1990.1189· OSTI ID:6494422

Takeyama, M ^[1]; Liu, C T ^[2]

---

1. National Research Institute for Metals, 2-3-12 Nakameguro, Meguro-ku, Tokyo 153 (Japan)
2. Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, TN (USA)

The microstructure and mechanical properties of several Ni-Al-Hf alloys in the composition range between NiAl({beta}) and Ni{sub 2}AlHf (Heusler phase) have been studied. The volume fraction of Heusler phase, {ital V}{sub {ital f}}, in these alloys varies from about 15 to 96%. The lattice misfit between the {beta} and Heusler phases in two-phase alloys is larger than 5%, indicating no coherency between them. The yield strength increases with increasing {ital V}{sub {ital f}} at all temperatures to 1000 {degree}C. Compressive ductilities of 4 and 7% were obtained for the alloy with {ital V}{sub {ital f}} of 15% at room temperature and 500 {degree}C, respectively, but they decreased to 0% with increasing {ital V}{sub {ital f}} to 96%. The corresponding fracture mode is basically transgranular cleavage. However, all the alloys can be deformed extensively without fracture at 1000 {degree}C. The hardness of the Heusler alloy is very high (8.3 GPa) at room temperature, and it decreases gently with temperature to 600 {degree}C, followed by a rapid decrease to 1000 {degree}C. The brittleness and high hardness of the Ni{sub 2}AlHf Heusler phase at low temperatures are interpreted in terms of internal lattice distortion resulting from its crystal structure. The thermally activated process of deformation takes place above 600 {degree}C, which is responsible for the rapid drop of the hardness of the alloys.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6494422
• Journal Information: Journal of Materials Research; (USA), Vol. 5:6; ISSN 0884-2914
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
MECHANICAL PROPERTIES
MICROSTRUCTURE
HAFNIUM ALLOYS
NICKEL ALLOYS
CRYSTAL LATTICES
FRACTURE PROPERTIES
HARDNESS
HEUSLER ALLOYS
QUANTITY RATIO
ALLOYS
COPPER ALLOYS
COPPER BASE ALLOYS
CRYSTAL STRUCTURE
MANGANESE ALLOYS
360102* - Metals & Alloys- Structure & Phase Studies
360103 - Metals & Alloys- Mechanical Properties