JOULE HEATING IN AMORPHOUS METALLIC WIRES

Non-conventional heating treatments, such as Joule heating, can produc e 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 annealin g temperature. The temperature behaviour of two selected wires submitt ed to a DC electrical current of increasing amplitude was calibrated b y comparing the temperature dependence of the material's saturation ma gnetization obtained during Joule heating to that measured during conv entional annealing in a furnace. As a result, a correlation between th e average temperature and current density was obtained. A theory descr ibing the thermal effects of a continuous current flow in amorphous wi res is proposed, showing that the thermal treatment is nearly uniform over the entire wire volume, under typical experimental conditions. Th e effect of fluctuations of the wire diameter on the steady-state temp erature is also discussed.