Isokinetic Analysis of Fe41Co7Cr15Mo14Y2C15B6 Bulk Metallic Glass: Effect of Minor Copper Addition.

Parisa Rezaei-Shahreza,Marcin Nabiałek,Zahra Jaafari,Amir Seifoddini,Agata Śliwa,Saeed Hasani

doi:10.3390/ma13173704

Parisa Rezaei-Shahreza, Marcin Nabiałek + Show 4 more

Open Access

https://doi.org/10.3390/ma13173704

Copy DOI

Abstract

In the present study, (Fe41Co7Cr15Mo14Y2C15B6)100−xCux (x = 0, 0.25 and 0.5 at.%) amorphous alloys were prepared by copper-mold casting. To clarify the effect of the minor addition of copper on the mechanism of nucleation and growth during the crystallization process, an isokinetic analysis was performed. The activation energies (E) of the various crystallization stages were calculated by using theoretical models including Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), Augis–Bennett and Gao–Wang methods. In addition, Augis–Bennett, Gao–Wang and Matusita methods were used to investigate the nucleation and growth mechanisms and to determine other kinetic parameters including Avrami exponent (n), the rate constant (Kp) and dimensionality of growth (m). The obtained results revealed that the activation energy—as well as thermal stability—was changed with minor addition of copper. In addition, the obtained Avrami exponent values were confirmed by Johnson–Mehl–Avrami–Kolmogorov (JMAK) method. The research findings demonstrated that the value of Avrami exponent is changed with minor addition of copper, so that the Avrami exponents of all crystallization stages, except the second peak for copper-free amorphous alloy, were equal to integer values ranging from two to four, indicating that the growth mechanisms were controlled by interface. Moreover, the kinetic parameters of n and b for all peaks were increased by an increase in crystallization temperature, which can be attributed to the increase in the nucleation rate.

Highlights

In recent years, many attempts have been made to generate new amorphous alloys and bulk metallic glasses (BMGs) with better properties and performance [1,2,3]
As previously discussed in detail, the thermal stability and glass forming ability (GFA) is increased by the minor addition of copper [17], which is in good agreement with that of the obtained for Tg
Activation energies of the investigated BMGs in various crystallization stages were measured by various kinetic methods such as; FWO, KAS, Augis–Bennett and Gao–Wang methods

Summary

Introduction

Many attempts have been made to generate new amorphous alloys and bulk metallic glasses (BMGs) with better properties and performance [1,2,3] These efforts have led to the design and development of advanced BMGs with special properties such as high strength and hardness [4,5,6,7], relatively good corrosion resistance [8,9,10] and excellent magnetic properties [11,12,13]. In BMGs with a maximum nucleation and the minimum growth rates, crystallization process can take place partially by controlling the kinetic parameters and as a result an amorphous matrix nanocomposite can be produced with excellent mechanical and magnetic properties [27,28,29]. Lesz et al [32] studied the effect of

Methods

Results

Conclusion