Tensile and creep rupture properties of Co + Co{sub 3}AlC{sub 0.5} two-phase alloys

Conference · Thu Jul 01 04:00:00 EDT 1999

OSTI ID:20001614

Ishibashi, R; Nakamura, S; Aono, Y; Miura, S; Mishima, Y

It is expected that the {kappa}-phase of the intermetallic compound Co{sub 3}AlC{sub 0.5} would strengthen Co-base alloys used at high temperatures like the {gamma}{prime}-phase of Ni-base superalloys. Tensile and creep rupture properties of Co+{kappa} two-phase alloys with {kappa}-phase volume fractions up to 0.75 were investigated. Alloy samples made by directional solidification casting were annealed at 1,573K for 3.6 ks and at 1,373K for 28.8 ks in vacuum, followed by Ar gas cooling. Tensile tests at RT and 1,073K and creep rupture tests at 1,089K under a stress of 172 MPa were conducted with the tensile axis parallel to the solidification direction. In alloys with low {kappa}-phase volume fraction, cuboidal {kappa}-precipitates with average particle diameters of 0.4 to 1.0 {micro}m were observed. They were coherent with the Co(fcc) matrix with misfits of about 3%. As the {kappa}-phase volume fraction increased, tensile strength also increased. The alloy with {kappa}-phase volume fraction of 0.4 had a 0.2% proof stress of 817 MPa, tensile strength of 1,047 MPa at RT, creep rupture life of 1.43 Ms, and tensile strain higher than 10%. These strengths are better than those of the conventional Co-base alloys. However, ductility of alloys with {kappa}-phase volume fraction larger than 0.4 decreased due to large eutectic and primary {kappa}-phase particles.

• Research Organization: Hitachi, Ltd. (JP)
• OSTI ID: 20001614
• Report Number(s): CONF-981104--; ISBN 1-55899-458-0; ISSN 1067-9995
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CARBON ADDITIONS
COBALT ALLOYS
CREEP
EXPERIMENTAL DATA
INTERMETALLIC COMPOUNDS
MICROSCOPY
MICROSTRUCTURE
PHASE DIAGRAMS
PRECIPITATION
TENSILE PROPERTIES