Effect of creep deformation on creep-fatigue damage in lamellar TiAl alloy

Citation
Ys. Park et al., Effect of creep deformation on creep-fatigue damage in lamellar TiAl alloy, MATER TRANS, 42(7), 2001, pp. 1380-1384
Citations number
18
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Material Science & Engineering
Journal title
MATERIALS TRANSACTIONS
ISSN journal
1345-9678 → ACNP
Volume
42
Issue
7
Year of publication
2001
Pages
1380 - 1384
Database
ISI
SICI code
1345-9678(200107)42:7<1380:EOCDOC>2.0.ZU;2-6
Abstract
In order to investigate the low cycle fatigue behavior of lamellar structur ed Ti-46.6Al-1.4Mn-2Mo (at%) alloy, total strain range controlled creep-fat igue and continuous fatigue tests (R = -1, strain rate = 4 x 10(-3) s(-1)) were carried out at 800 degreesC. A drastic reduction of fatigue life is ob served in creep-fatigue test compared with continuous fatigue test. Microst ructural and compositional changes during the creep-fatigue test were inves tigated using SEM, TEM and AES (auger electron spectroscopy). It was found that this reduction of fatigue life in creep-fatigue test was understood to be due to the additional creep damage occurring during tensile hold time. Recent reports indicate that the lamellar TiAl alloy has a different creep deformation mechanism from general metallic materials. For the lamellar TiA l alloy, it has been reported that creep deformation is controlled not by t he self-diffusion assisted dislocation climb but by the dislocation generat ion due to the alpha (2) --> gamma phase transformation at the lamellar int erface. This implies that creep damage induces microstructural phase change during which moving dislocations are generated for the continuous deformat ion. Therefore, it is very important to investigate the effect of creep def ormation on creep-fatigue damage in terms of microstructural change. In the present study, microstructural analysis using SEM, TEM and AES (auger elec tron spectroscopy) for compositional analysis were conducted. It is found t hat, under creep-fatigue test, the creep damage causes alpha (2) --> gamma phase transformation at the grain boundary, from which inter.-ranular crack s are initiated to control the creep-fatigue behavior.