Abstract

A nanostructured Ni-11.3Fe-1.4W alloy deposit was obtained from an ammonium citrate bath at a current density of 600 mAcm-2. XRD analysis shows that the deposit contains an amorphous matrix having embedded nanocrystals of the FCC phase of the solid solution of Fe and W in Ni with the average crystal grain size of 8.8 nm. The deposit has a high internal microstrain value and a high minimum density of chaotically distributed dislocations. The effect of milling and annealing of the Ni-11.3Fe-1.4W alloy on electrical and magnetic properties was studied. Structural changes in the alloy take place during both annealing and milling. Upon deposition, the alloy was heated to 420?C. Heating resulted in structural relaxation which induced a decrease in electrical resistivity and an increase in magnetic permeability of the alloy. Further heating of the alloy at temperatures higher than 4200C led to crystallization which caused a reduction in both electrical resistivity and magnetic permeability. The milling of the alloy for up to 12 hours caused a certain degree of structural relaxation and crystallization of the alloy. The increase in crystal grain size up to 11 nm and the partial structural relaxation induced a decrease in electrical resistivity and an increase in magnetic permeability of the alloy. Heating the powders obtained by milling at 4200C led to complete structural relaxation, reduced electrical resistivity, and increased magnetic permeability. During heating of the powders obtained by milling at temperatures above 420?C, crystallization and a significant increase in crystal grain size occurred, leading to a reduction in both electrical resistivity and magnetic permeability. The best magnetic properties were exhibited by the alloys milled for 12 hours and annealed thereafter at 420?C. In these alloys, crystal grains were found to have an optimum size, and complete relaxation took place, resulting in a maximum increase in magnetic permeability.

Highlights

  • Nanostructured powders of different alloys are widely used in novel technologies due to their specific combinations of electrical, magnetic, catalytic, corrosion and other propertiesM

  • During heating of the powders obtained by milling at temperatures above 4200C, crystallization and a significant increase in crystal grain size occurred, leading to a reduction in both electrical resistivity and magnetic permeability

  • A nanostructured Ni–11.3Fe–1.4W alloy was obtained by electrodeposition from an ammonium citrate electrolyte at a current density of 600 mA cm-2

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Summary

Introduction

Nanostructured powders of different alloys are widely used in novel technologies due to their specific combinations of electrical, magnetic, catalytic, corrosion and other propertiesM. Nanostructured powders of different alloys are widely used in novel technologies due to their specific combinations of electrical, magnetic, catalytic, corrosion and other properties. Nanostructured nickel/iron/tungsten alloys are characterized by good electrical and magnetic properties, high corrosion and heat stability, and high catalytic activity for the cathodic evolution of hydrogen [6,7,8,9,10,11,12,13,14,15,16,17]. Other procedures for their production have been developed, such as mechanical alloying, sputtering or electrolytic deposition from water baths [6,7,8,9,10,11,12,13,14,15,16,17]. The electrolytic procedure seems to be the most convenient method for the production of this alloy

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