The effect of hold time and waveform on the high-temperature, low-cycle fatigue properties of a Nb-A286 alloy

Citation
Bs. Rho et al., The effect of hold time and waveform on the high-temperature, low-cycle fatigue properties of a Nb-A286 alloy, MET MAT T A, 32(10), 2001, pp. 2539-2546
Citations number
21
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science",Metallurgy
Journal title
METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE
ISSN journal
1073-5623 → ACNP
Volume
32
Issue
10
Year of publication
2001
Pages
2539 - 2546
Database
ISI
SICI code
1073-5623(200110)32:10<2539:TEOHTA>2.0.ZU;2-N
Abstract
The effect of hold time and waveform on the high-temperature, low-cycle. fa tigue (HTLCF) of a Nb-modified A286 alloy was investigated at 650 degreesC. It was found that the fatigue life with strain hold was lower than that of continuous low-cycle fatigue, and this was due to the additive creep defor mation during hold time. The apparent activation energy for the creep defor mation during the tensile, and compressive hold times was determined to be about 260 to 270 kJ/mole from stress-relaxation curves. This value is in go od agreement viith the apparent activation energy required for the formatio n of eta phase at the grain boundary in the Nb-A286 alloy. Therefore, the g rain-boundary precipitates and the corresponding cavitation along the grain boundary were estimated to be the main damage of the creep-fatigue interac tion of the Nb-A286 alloy and to cause the intergranular failure. Also, the driving force for grain-boundary cavitation leading to intergranular failu re under a compressive strain hold is reduced compared to the case of a ten sile strain hold. This fact is known to be due to the healing effect of the grain-boundary cavitation. Therefore, the strain hold in compression leads to less, reduction in fatigue life than that in tension.