The Influence of 3d and 4d Transition Metals on the Glass Forming Ability of Ternary FeCo-Based Alloys

Z Śniadecki

doi:10.1007/s11661-021-06196-7

Abstract

Thermodynamic modeling was used to determine enthalpies of formation and other thermodynamic parameters describing glass forming ability of Fe-Co-TM (TM = V, Nb, Cr, Mo) alloys. FeCo-based alloys are considered as candidates for applications as high magnetic flux density materials due to their high magnetic saturation and low magnetic anisotropy. Nevertheless, mechanical properties, especially the lack of ductility, are their main weakness. Therefore, further optimization by vitrification, further heat treatment and alloying should be considered. As the most crucial step is the synthesis of amorphous precursors, discussion is concentrated on the effect of transition metal substitution on the glass forming ability. The highest glass forming ability was reported for Fe-Co-Nb alloys. It can be also noted that the driving force for vitrification can be improved by substitution of Fe by other transition elements, as glass forming ability parameter ∆PHS reaches the lowest values for Fe-less compositions.

Highlights

WELL-KNOWN FeCo-based alloys, which crystallize in bcc structure, possess high magnetic saturation of about 2.4 T
The results presented in this paper, where formation enthalpies were determined for Fe-Co-TM (TM = V, Cr, Nb, Mo) system, can serve as a roadmap for further development of amorphous films with specific structure and morphology
Determined phase diagrams and calculated glass forming abilities of numerous ternary alloys can be used as a key element to design composition of amorphous FeCo-based films with specific structure and morphology

Summary

INTRODUCTION

WELL-KNOWN FeCo-based alloys, which crystallize in bcc structure (called Permendur), possess high magnetic saturation of about 2.4 T. In combination with their low magnetic anisotropy, these materials are of interest for electrotechnical industry, where high magnetic flux density is needed (e.g., generators), even considering slightly increased cost due to high Co content.[1] Their properties, mechanical, can be further improved by alloying, with Hiperco as one of the examples.[2] Further improvement of deformability or fracture strength with subsequent optimization of resistivity and coercivity is connected with vitrification.[3,4,5] FeCo-based amorphous alloys can be synthesized by typical physical methods utilizing quenching of molten alloy or by sputtering.[3,6] FeCo alloy is a poor glass former, glass forming ability (GFA) have to be improved by addition of other elements such as B, Si, or other transition metals, as for example Zr or Ta.[7,8,9] Amorphous particles, pure FeCo alloys, were prepared by chemical methods through chemical reduction of metal ions with KBH4 and NaBH4 in aqueous solution.[10,11] such materials are promising candidates as energy harvesters[12] or even in medical. Presented results are the extension of previous studies undertaken for Fe-Ni-based systems.[22]

CALCULATIONS

RESULTS AND DISCUSSION

CONCLUSIONS