Fe-Al materials for structural applications at high temperatures: Current research at MPIE

Fe-Al-based materials possess a number of properties which make them highly interesting for the development of new light-weight structural materials. However, lack of strength at high temperatures and limited ductility at ambient temperatures so far has hindered any wider application of these materials. Recent progress achieved within an inter-departmental research initiative at the Max-Planck-Institut fur Eisenforschung GmbH is reviewed here. Based on a sound knowledge of physical and thermodynamic properties and careful analysis of the phase equilibria, various alloy systems have been investigated which offer different mechanisms for strengthening Fe-Al-based materials at high temperatures. By applying these mechanisms Fe-Al-based alloys with sufficient strength for structural applications at least between 650-800 degrees C have been developed. For these alloys processing routes such as rolling and forging have been demonstrated. Low ductility is still a crucial issue, but measures exist for improving ductility, e.g. by refining the microstructure through thermo-mechanical treatment. It has also been shown that iron aluminides not only show superior Corrosion resistance in oxidising and sulphidising atmospheres but also in other hostile environments like carburising atmospheres and under molten salts.