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Mechanical alloying of the FeNi-Ag system

Abstract:

The Fe-Ni-Ag system is of particular interest for its potential applications as soft magnetic granular material with small magnetic grains embedded in a non-magnetic metal matrix. Under equilibrium conditions: Fe-Ag and Ni-Ag are immiscible and Fe-Ni shows complete solubility. These materials are particularly important for magnetoresistivity properties. The properties of these alloys are closely related to their microstructure; therefore, a detailed study of the transformations occurring during milling was undertaken using pre-alloyed FexNi100-x (x = 30, 50 and 70) further milled with different Ag content to give the following alloys compositions (Fex-Ni100-x)100-yAgy (y = 5, 20, 60). Consolidation of the mechanically alloyed powders by sintering at 950 °C was performed. Morphological and structural characterization of the sintered powders was carried out by scanning and transmission electron microscopy and X-ray diffraction. Fe30Ni70 and Fe50Ni50 formed ordered FeNi3 compound. Fe70Ni30 showed the formation of a mixture of γ-(Fe,Ni) and α-Fe(Ni) solid solutions. The mixture of these systems with Ag showed the metal solid solutions surrounded by Ag islands of FexNiy-Ag, There was also evidence of Ag diffusing into the γ-(Fe,Ni). High Ag content (60%) shows formation of islands of FeNi surrounded by Ag. Sintering is always improved with the Ag content. © 2006 Elsevier B.V. All rights reserved.