Creep deformation behavior of an oxide dispersion strengthened modified iron aluminide alloy

Abstract

The present investigation highlights the creep deformation behavior of the yttria dispersion strengthened iron aluminide alloy in the temperature range of 600–700 ◦C at different stress levels. A relatively higher value of apparent Norton exponent (~9 at 600 ◦C, 12.6 at 650 ◦C and 12.9 at 700 ◦C) of the investigated alloy has been rationalized with the incorporation of the concept of the threshold stress. After determining the threshold stress value of 103.6 MPa at 600 ◦C, 84.2 MPa at 650 ◦C and 74 MPa at 700 ◦C, the true Norton exponent value has been found as ~3, which estimates the occurrence of glide-controlled creep mechanism in the investigated alloy. The TEM investigation of creep-tested sample substantiate the aforementioned governing creep deformation mechanism. The apparent activation energy for creep deformation has been found to be higher (~613.7 kJ/mol) in the temperature range of 600–625 ◦C, and relatively lower (~310.9 kJ/mol) in the temperature range of 650–700 ◦C. However, the true value of activation energy for creep deformation has been identified to be constant (~44.2 kJ/mol) in the temperature range of 600–700 ◦C. Both the Modified Monkman-Grant relation and microscopic investigations of the investigated alloy have revealed a stable microstructural feature after creep deformation, which comprises nanometer-sized Y2O3 within the iron aluminide matrix. The Kernel Average Misorientation analyzed through EBSD analysis of the creep-tested samples have been correlated with the apparent Norton exponent and activation energy for creep deformation.