Effects of tungsten addition on crystallization, magnetic and electrical transport properties of amorphous Fe81-xWxSi9B10 alloys

The work is focussed on the influence of tungsten on magnetization, electrical transport resistivity, crystallization process and conditions of its optimisation in amorphous Fe-W-Si-B alloy. The samples were melt-quenched ribbons 24 mu m in thickness and 12-15 mm in wide. The structure was checked by XRD. The microstructure was evidenced for as-cast and annealed sample by TEM and ED. The magnetization and electrical resistivity were made in-situ during sample annealing between 300 K and 1100 K. The Curie temperature was estimated from the inflexion point of the first rapid demagnetization. For electrical resistivity measurements the conventional four-probe DC technique was used. The crystallization temperatures were determined from temperature dependence of magnetization and electrical resistivity. In the samples without or with low W content, lower than 5.5 at %, the precipitation of alpha-Fe in a first crystallization step started earlier than it was expected and it was accelerated probably by the formation of a solid solution phase saturated with bor. During second crystallization step Fe (W)-B small crystallites larger in size but less in the percentage than of alpha-Fe (W) phase are formed. The W addition at the expense of Fe causes the Curie temperature of Fe-W-Si-B alloys to decrease significantly.