Kinetics and mechanisms of creep in hot isostatically pressed niobium carbide

Conference · Tue Jan 01 00:00:00 EST 1985

OSTI ID:6371304

Nixon, R D; Davis, R F; Bentley, J

Constant compressive stress creep experiments in the temperature and stress ranges of 1730K to 2100K and 16 MN/m/sup 2/ to 70 MN/m/sup 2/ on HIPed NbC/sub 0.74/ have revealed stress exponents of 2.0 under stress levels of 16 to 54 MN/m/sup 2/ at all temperatures investigated and 3.2 under stress levels of 54 to 70 MN/m/sup 2/ at 1830K. The activation energy of steady state creep is approximately 230 kJ/mol in the temperature range of 1730K to 1930K under 48 to 54 MN/m/sup 2/ and 470 kJ/mol in the temperature range of 1900K to 2100K under 64 MN/m/sup 2/. TEM of the annealed but uncrept material reveals grown-in dislocation subboundaries. At 1730K and under 34 to 54 MN/m/sup 2/ the subboundaries evolve into simple tilt boundaries which are occasionally knitted, indicating more glide activity at higher stresses. At 1930K and under 34 to 54 MN/m/sup 2/, hexagonal subboundaries form, but are not as well defined as in the annealed material. At 2100K and under 16 to 30 MN/m/sup 2/, the subboundaries are well-defined hexagonal networks which become polygonized under higher stresses on 64 MN/m/sup 2/. The experimental and TEM results indicate that at low temperatures (below 0.5 T/sub m/ = 2073K) and at all stresses, creep occurs by dislocation glide which is accompanied by subgrain and high angle boundary interaction. At high temperature (above 0.5 T/sub m/), strain occurs by glide and subboundary movement; recovery occurs by climb in the subboundary.

• Research Organization: North Carolina State Univ., Raleigh (USA). Dept. of Materials Engineering; Oak Ridge National Lab., TN (USA)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 6371304
• Report Number(s): CONF-851217-70; ON: TI87011649
• Resource Relation: Conference: Materials Research Society meeting, Boston, MA, USA, 2 Dec 1985
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
NIOBIUM CARBIDES
CREEP
ACTIVATION ENERGY
DISLOCATIONS
HOT PRESSING
MICROSTRUCTURE
TEMPERATURE DEPENDENCE
TRANSMISSION ELECTRON MICROSCOPY
VERY HIGH TEMPERATURE
CARBIDES
CARBON COMPOUNDS
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
ELECTRON MICROSCOPY
ENERGY
FABRICATION
LINE DEFECTS
MATERIALS WORKING
MECHANICAL PROPERTIES
MICROSCOPY
NIOBIUM COMPOUNDS
PRESSING
REFRACTORY METAL COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
360203* - Ceramics
Cermets
& Refractories- Mechanical Properties