The Effect of High-Temperature Deformation on the Structure of Iron Aluminides

Abstract

The iron aluminides are very perspective materials with many advantages – for example excellent corrosion resistance and/or good strength up to 600 °C. Due to these benefits they appear as suitable materials for use in high temperature applications. But some negative properties (sharp drop in strength above 600 °C or limited ductility at room temperature) are the major obstacles for their use. One way, how to improve mechanical properties of iron aluminides, is doping of binary alloy by alloying elements, which can form strengthening precipitates. Depending on their size the precipitates of secondary phases can block dislocation movement or act as strengthening phase as known in composite materials.One from many properties, which is important to know before a new type of material is used in structural applications, is its deformation behaviour. In present paper there was studied the structure of Fe-25Al-5Zr (in at. %) sample in as cast state and in states after high-temperature deformation at 600 and 800 °C in detail. A high resolution SEM equipped with EDX and EBSD was used for the study of structure. It was measured that huge grains are presented in the structure of as cast state. After deformation at 600 °C there were still observed huge Fe3Al-matrix grains, but strongly deformed. Also formation of sub-grains due to deformation is obvious. Deformation at 800°C led to formation of small grains due to recrystallization. Higher deformation degree in non-eutectic areas led to preferential recrystallization while Fe3Al phase in eutectic regions remained deformed (nonrecrystallized).