Abstract:The effects of Mo addition on microstructures, phase relationships, order–disorder phase-transition temperatures and room-temperature mechanical properties of Fe₅₀Al_50-nMo_n alloys (n=1, 3, 5, 7, and 9, mole fraction, %) were investigated after solidification and heat treatment. Structural characterization of the samples was performed via X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calorimetry. Room-temperature mechanical properties were investigated by conducting compression and microhardness tests. Mo₃Al particles precipitated in all alloys because of the limited solid solubility of Mo in the Fe-Al-based phases. The as-cast Fe₅₀Al_50-nMo_n alloys exhibited brittle behavior with high yield strength and limited fracture strain at room temperature. Compared with the as-cast alloys, all the heat-treated alloys except for the Fe₅₀Al₄₁Mo₉ alloy exhibited enhanced mechanical properties at room temperature. The heat-treated Fe₅₀Al₄₃Mo₇ alloy exhibited the highest fracture strain and compressive strength of 25.4% and 2.3 GPa, respectively.

Key words: iron aluminides; microstructure; order–disorder phase transformation; compressive properties