On dc Joule-heating effects in amorphous glass-covered Fe77.5Si7.5B15 microwires

The thermal effects of Joule-heating treatment on Fe77.5Si7.5B15 amorphous glass-covered microwires (AGCMs) are examined and, taking into account the appropriate boundary conditions at the metal–glass interface, a general solution of the equation describing the evolution of the sample temperature in the course of electrical direct current (dc) Joule-heating is found. A theoretical and thermo-numerical model for the calculation of the distribution of temperature in an AGCM through which an electrical current (dc) passes has been developed. This was done for the amorphous state (for sample temperature values below that corresponding to the onset of the crystallization process) and also for the transition from the amorphous to the crystalline phase (for both isothermal and non-isothermal processes) using the Johnson–Mehl–Avrami model. In the non-isothermal crystallization process, three crystallization products (αFe(Si), Fe2B and Fe23B6) were found, corresponding to the three stages of this process.

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