Investigation of creep deformation mechanisms and environmental effects on creep resistance in a Ti2AlNb based intermetallic alloy

• Published in: Intermetallics 2004-03, Vol.12 (3), p.261-274
• Main Authors: Yang, Seung Jin, Nam, Soo Woo, Hagiwara, Masuo
• Format: Article
• Language: English
• ISSN: 0966-9795
• DOI: 10.1016/j.intermet.2003.10.009

Creep deformation mechanisms and environmental effects of Ti2AlNb based intermetallic alloys are investigated. Two different creep deformation mechanisms operate in accordance with elevating temperatures in the range of 600-800 deg C. Below 700 deg C, dislocation climb by pipe-diffusion may control the creep deformation. A sharp drop of creep resistance is observed above 700 deg C in an air environment. This abnormal acceleration in creep rate may be due to the abundant supply of easily mobile dislocations on the prismatic plane provided by the bee to O phase transformation. Therefore, the creep deformation mechanism above 700 deg C may be considered to be the bcc to O phase transformation that generates prismatic dislocations. The creep resistance in a vacuum environment is superior to that in the air environment, especially at temperatures above 700 deg C. This may be because the limited oxygen level in a vacuum environment can keep the bcc phase stable at such temperatures. Therefore, prismatic dislocations to control and accelerate creep rate above 700 deg C are not supported by the bcc to O phase transformation and the creep resistance can be enhanced.