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Resistivity Model of Phase Transformation of Amorphous Al78W22 Thin Films under Isothermal Conditions

Phase transformation and crystallization kinetics of the amorphous Al78W22 thin films under isothermal conditions was examined by continuous in situ electrical resistance measurements. The sample preparation was performed by magnetron codeposition. The resistivity of the samples was monitored during isothermal annealing at 803, 813 and 823 K, respectively, i.e. at the temperatures where the crystalline phase starts to develop. The temperature dependence of the resistivity ˆ(T) was estimated from isochronal measure-ments while the volume fraction of crystalline phase ˆ(x, t) was established using a general two phase resistivity model for this system and estimated from isothermal measurements. Combinations of these two approaches were used for modeling of the resistivity variation during cooling cycles. The activation energy for crystallization and the reaction order were determined within the framework of the JMA theory. The results indicated that the crystalliza-tion mechanism in isothermal heating was diffusion–controlled process with steady–state nucleation.

Aluminum-tungsten; amorphous alloys; thin films; phase transformation

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