Effect of Zr content on the precipitation and dynamic softening behavior in Al-Fe-Zr alloys

In this paper, the precipitation and dynamic softening behavior of Al-Fe-Zr alloys were investigated by transmission electron microscopy (TEM), electron back scattering diffraction (EBSD), and the precipitation thermodynamics was studied by JmatPro software. Results show that the optimizing temperature of Al3Zr precipitates was 350 degrees C and the fraction of butterfly-shaped Al3Zr and rod-shaped Al3Fe reached a peak at similar to 350 degrees C. With the increase of Zr content, the fraction of Al3Zr increased, whereas its size and morphology had almost no change. The fraction and morphology of Al3Fe showed less variation with Zr content. Dynamic recovery and dynamic recrystallization occurred during extrusion. The two kinds of precipitation particles in aluminum matrix pinned the dislocations and inhibited dynamic recrystallization effectively. As the Zr content went up from 0.1 to 0.4 wt %, the inhibition got stronger and the fraction of recrystallized grains decreased from 44.2% to 86.9%. As a consequence of the dynamic recrystallization suppression, dynamic recovery became the major softening mechanism.