Structural and phase analysis of rapidly solidified Al-Fe alloys

The structure and phase composition of lightly-doped Al-Fe alloys obtained by ultrarapid quenching from the melt are investigated. The surface of foils was studied using scanning electron microscopy, atomic-force microscopy, and Rutherford backscattering technique. The variation in the phase composition of alloys during annealing was studied by x-ray diffraction technique and by resistivity and microhardness measurements. The Al-Fe alloys have microcrystalline structure with a nonuniform iron content in the near-surface region of the samples. A correlation of depth profiles of iron and phase composition of the foils is observed. It is found that decomposition of the supersaturated α solid solution proceeds in the temperature range 250–350°C. As the annealing temperature increases, a metastable Al6Fe phase is precipitated. In the range 300–500°C, the metastable Al6Fe phase decomposes, and a stable Al3Fe phase is precipitated.