Phase transformation of a dual phase Al-Fe alloy prepared by mechanical alloying

A metastable Al90Fe10 (at.%) alloy, composed of a supersaturated solid solu tion of face-centred cubic (fcc) Al(Fe) and an amorphous phase matrix, was prepared by mechanical alloying of a mixture of Al and Fe elemental blends. The thermally induced microstructural evolution in the dual phase alloy wa s characterized by X-ray diffraction, transmission electron microscopy, dif ferential scanning calorimetry, and magnetothermal analysis. On continuous heating two stages of solid state phase transformation occurred: (i) a poly morphous crystallization of the amorphous phase to a metastable crystalline Al6Fe that structurally stabilizes over a temperature range of about 200 K , and (ii) a eutectoid decomposition of the crystalline Al6Fe into the equi librium phases of Al13Fe4 and fcc Al(Fe). Thermodynamic and kinetic analyse s of the observed phase transformation processes were given. The formation of the dual phase alloy in the as-milled state and the phase transitions ca n be illustrated by a hypothetical free energy diagram, implying the dual p hase structure facilitates the polymorphous crystallization of Al6Fe.