The phase change of metastable Al
6Fe or Al
mFe into stable Al
3Fe was investigated in Al-0.5%Fe alloys having either Si up to 0.11% or Mg up to 1.2%. Specimens containing Al
6Fe or Al
mFe were prepared by unidirectional solidification and isothermally annealed at 600°C. Progressive changes in the eutectic structures were examined by means of optical and transmission electron microscopies, and X-ray diffraction method.In Si containing alloys, the phase change is accelerated with increasing Si contents, where stable Al
3Fe is found in the eutectic region to form in the cast state and to grow at the expense of metastable phases. In contrast to this, in Mg containing alloys, the phase change is markedly suppressed with increasing Mg contents, where the diffusion of Featoms in the matrix is suggested to be largely restrained due to interactions with Mg atoms. In all cases, the time required for the phase change is shorter in Al
mFe than in Al
6Fe.
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