Structural Evolution in Wet Mechanically Alloyed Co-Fe-(Ta,W)-B Alloys

Vladimír Girman,Miloš Matvija,Pavol Sovák,Maksym Lisnichuk,Jozef Bednarčík,Daria Yudina

doi:10.3390/met11050800

Abstract

In the present study, the effect of wet mechanical alloying (MA) on the glass-forming ability (GFA) of Co43Fe20X5.5B31.5 (X = Ta, W) alloys was studied. The structural evolution during MA was investigated using high-energy X-ray diffraction, X-ray absorption spectroscopy, high-resolution transmission electron microscopy and magnetic measurements. Pair distribution function and extended X-ray absorption fine structure spectroscopy were used to characterize local atomic structure at various stages of MA. Besides structural changes, the magnetic properties of both compositions were investigated employing a vibrating sample magnetometer and thermomagnetic measurements. It was shown that using hexane as a process control agent during wet MA resulted in the formation of fully amorphous Co-Fe-Ta-B powder material at a shorter milling time (100 h) as compared to dry MA. It has also been shown that substituting Ta with W effectively suppresses GFA. After 100 h of MA of Co-Fe-W-B mixture, a nanocomposite material consisting of amorphous and nanocrystalline bcc-W phase was synthesized.

Highlights

Amorphous alloys are still the subject of scientific interest due to their outstanding combinations of physical, chemical, electrochemical and mechanical properties such as high tensile strength and hardness, extreme elastic strain limit [1,2], or higher corrosion resistance [3,4]
Co-based amorphous alloys are interesting for their magnetic behavior, like their high permeability, excellent soft magnetic properties, i.e., extraordinary low coercive force of 0.25 A/m, zero magnetostriction [7], giant magnetoimpedance [8] and excellent corrosion resistance [2]
The phases were identified with the help of the Crystallographic Open Database (COD) [30]

Summary

Introduction

Amorphous alloys are still the subject of scientific interest due to their outstanding combinations of physical, chemical, electrochemical and mechanical properties such as high tensile strength and hardness, extreme elastic strain limit [1,2], or higher corrosion resistance [3,4]. Co-Fe-Ta-B alloys show the best glass-forming ability (GFA) and wide supercooled liquid region of 70 K [5] Along with this, they exhibit the highest values of compressive yield strength (over 5000 MPa) [6]. Co-based amorphous alloys are interesting for their magnetic behavior, like their high permeability, excellent soft magnetic properties, i.e., extraordinary low coercive force of 0.25 A/m, zero magnetostriction [7], giant magnetoimpedance [8] and excellent corrosion resistance [2]. For these reasons, they are the subject of lasting experimental study. In order to further enhance its GFA, a few research groups investigated the effect of alloying base alloy composition Co43Fe20Ta5.5B31.5 by selected elements: Mo, Si [6], Cr, Si [11], Nb [12], Cu, Si [13], Ni, Si [14], Ni, Nb, Si [15]

Methods

Results

Conclusion