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 °C. Below 700 °C, dislocation climb by pipe-diffusion may control the creep deformation. A sharp drop of creep resistance is observed above 700 °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 bcc to O phase transformation. Therefore, the creep deformation mechanism above 700 °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 °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 °C are not supported by the bcc to O phase transformation and the creep resistance can be enhanced. © 2003 Elsevier Ltd. All rights reserved.
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