The Effect of Cr Content on the Glass Forming Ability of Fe68-xCrxNb8B24 (x =8,10,12) Alloys

Marcio Andreato Batista Mendes,Walter José Botta Filho,Carlos Alberto Caldas De Souza,Ana Karla Melle,Claudio Shyinti Kiminami,Régis Daniel Cava,Claudemiro Bolfarini

doi:10.1590/1980-5373-mr-2016-0290

Abstract

Based on the Fe60Cr8Nb8B24 alloy, reported in the literature as good Glass Forming Ability (GFA), in this study the GFA of two new compositions was proposed, Fe68-xCrxNb8B24 (x=10,12). They were evaluated as good candidates to be new compositions of Bulk Metallic Glasses (BMG) with better corrosion resistance due to the high Cr content. Rapidly solidified glassy ribbons were processed, and based on their thermal characteristics, the critical thickness of the glassy structure formation (Zc) was estimated. The critical thickness (Zc) obtained experimentally using the wedge-shaped casting method was evaluated and it presented a much lower value than that estimated theoretically. However, the GFA of the compositions analyzed was ranked and this ranking (i.e. whichever has the most or least GFA) is in agreement with the result predicted theoretically. The GFA of Fe58Cr10Nb8B24, which presented a maximum thickness of the amorphous region of wedge-shaped samples of about 0.6 mm (but estimated it would be 3.56 mm), offered good prospects to be a new Fe-based glass former alloy which has better resistance to corrosion than the Fe60Cr8Nb8B24 alloy reported.

Highlights

Over the last few years, extensive research has been carried out to improve the properties of metallic glasses, such as the physical, chemical, magnetic and mechanical properties
In 1 N HCl solutions, the Fe67.6 C7.1Si3.3B5.5P8.7Cr2.3Mo2.5Al2.0Co1.0 alloy containing 2.3 at% Cr showed a corrosion resistance similar to the 304 stainless steel that contains high Cr (19 at% Cr) and Ni (9 at% Ni) contents[3]. This behavior indicates a promising replacement of stainless steel alloys by glassy alloys in various applications
This elastic strain criterion states that the mean local strain must exceed 0.054 in order to destabilize the crystal lattice formation and encourage amorphization[11,12]. Based on these modeling criteria and on the Fe60Cr8Nb8B24 alloy reported by Cheney and Vecchio[11] as a good Glass Forming Ability (GFA), for this study the Fe68-xCrxNb8B24 (x=10,12) compositions were considered as candidates to be new compositions of Bulk Metallic Glasses (BMG) with higher corrosion resistance due to the higher Cr content

Summary

Introduction

Over the last few years, extensive research has been carried out to improve the properties of metallic glasses, such as the physical, chemical, magnetic and mechanical properties. Regarding the design and selection of compositions in Fe-based BMG with additions of Cr, Nb and B elements, Cheney and Vecchio[11] reported a modeling criterion that simultaneously analyzes the thermodynamics and kinetics of the vitrification behavior in a potential glass-forming alloy.

Results

Conclusion