Transformation kinetics of rapidly quenched Al75Cu15V10 and Al55Mn20Si25 amorphous alloys to icosahedral phases were examined by differential scanning calorimetry and transmission electron microscopy. The transformation is analogous to the polymorphous transformation by homogenous nucleation and diffusionless growth. The Avrami exponent and activation energy for transformation were measured to be 1.7-2.0 and 2.5 eV, respectively, for both alloys. The activation energy for growth during the transformation was estimated to be about 2.6 eV for Al75Cu15V10 and 2.7 eV for Al55Mn20Si25. The difference in free energy between the amorphous and crystallines phases was estimated to be 1.6 times larger than that between the amorphous and quasicrystalline phases.
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