On the influence of crystal structure on creep in a Fe3Al -based alloy

摘要

Iron aluminides are well known for their resistance to high-temperature sulfidizing and oxidizing environments [1]. In order to take advantage of their excellent corrosion resistance at high temperatures it is important that these alloys also exhibit some high temperature strength; A basic understanding of the creep process in this material class is therefore required. At 28 at.% At, the iron aluminium system possesses a low temperature ordered phase which exhibits a DOj-structure [2-4]. At high temperatures the B2-structiire is stable [2-4]. The B2/iDOrtransition temperature is below 600°C. Since the creep behavior in this temperature range is of interest, itis important to understand how crystallographic order influences the creep process. In earlier studies of creep of binary FejAI [5,6] it was claimed that there is a change of creep mechanism when the order changes from DOi to B2. This change was accompanied by a change in apparent activation energy of creep and it was thought that an increase of order would result in an increase of apparent activation energy of creep. Thus the DCVmicrostructure was reported to show a higher apparent activation energy for creep than the B2-phase (606 kJ/mole and 376 kJ/mole, respectively [6]). The present study investigates the temperature and stress dependence of creep rate in the Fe3AI-based alloy FA-129 [7].