Dislocation structure and deformation mechanism for the anomalous yield behavior in Fe3Al intermetallic alloys

Abstract

It is well known that Fe3Al intermetallic compound shows an anomalous peak of the yield strength at about 500 degrees C. That is, the yield strengths increase with increasing deformation temperature in the range of 300 degrees C-500 degrees C, and then decrease at higher temperatures. The dislocation structure was examined by transmission electron microscopy, and high temperature mechanical properties were examined by tensile and load relaxation tests. The flow stress curves obtained from load relaxation tests were then analyzed in terms of internal variable deformation theory. It was found that the flow curves consisted of three micro-deformation mechanisms -i.e. inelastic deformation mode, plastic deformation mode and dislocation creep deformation mode, depending on both dislocation structure and deformation temperature. The flow curves could be well described by the constitutive equations of these three micro-deformation mechanisms based on the internal variable deformation theory.