Joule heating in amorphous metallic wires

Non-conventional heating treatments, such as Joule heating, can produce materials with attractive physical properties. Although extensively explored in amorphous wires and ribbons, one of the major drawbacks of the technique is the intrinsic difficulty in determining the annealing temperature. The temperature behaviour of two selected wires submitted to a DC electrical current of increasing amplitude was calibrated by comparing the temperature dependence of the material's saturation magnetization obtained during Joule heating to that measured during conventional annealing in a furnace. As a result, a correlation between the average temperature and current density was obtained. A theory describing the thermal effects of a continuous current flow in amorphous wires is proposed, showing that the thermal treatment is nearly uniform over the entire wire volume, under typical experimental conditions. The effect of fluctuations of the wire diameter on the steady-state temperature is also discussed.