Fe₃Al Iron Aluminides Alloyed with High Concentrations of V and Cr: Their Structure and High Temperature Strength

Abstract

Eight iron aluminide alloys with different contents of V and Cr were prepared up to 25 at. pct of both elements. The effect of the V and Cr concentration on the microstructure and mechanical properties was investigated by several complementary techniques. This investigation revealed that the microstructure of all the investigated alloys was comparable regardless of their chemical composition. All the alloys were in a solid solution condition without any major chemical inhomogeneity. For all alloys, a comparable grain size and D0₃ crystallographic structure was observed. In situ X-ray diffraction measurement revealed that the crystallographic structure was stable up to 1073 K (800 °C) regardless of the chemical composition. Mechanical testing showed that the compressive yield stress significantly increased with the increasing total sum of V plus Cr. Much higher values of yield stress were measured for symmetric concentrations of V and Cr when compared to non-symmetric ones. Eventually, it was shown that the formation of at least a rough system of the lattice positions occupation by four types of atoms in four sub-lattices derived from D0₃ is the most probable strengthening factor for alloys with symmetric concentrations of V and Cr.