The Effect of Zr Addition on Melting Temperature, Microstructure, Recrystallization and Mechanical Properties of a Cantor High Entropy Alloy.

Enrico Gianfranco Campari,Magdalena Lassinantti Gualtieri,Paolo Veronesi,Elena Colombini,Angelo Casagrande

doi:10.3390/ma14205994

Enrico Gianfranco Campari, Magdalena Lassinantti Gualtieri + Show 3 more

Open Access

https://doi.org/10.3390/ma14205994

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Abstract

The effect of Zr addition on the melting temperature of the CoCrFeMnNi High Entropy Alloy (HEA), known as the “Cantor’s Alloy”, is investigated, together with its micro-structure, mechanical properties and thermomechanical recrystallization process. The base and Zr-modified alloys are obtained by vacuum induction melting of mechanically pre-alloyed powders. Raw materials are then cold rolled and annealed. recrystallization occurred during the heat treatment of the cold-rolled HEA. The alloys are characterized by X-ray diffraction, electron microscopy, thermal analyses, mechanical spectroscopy and indentation measures. The main advantages of Zr addition are: (1) a fast vacuum induction melting process; (2) the lower melting temperature, due to Zr eutectics formation with all the Cantor’s alloy elements; (3) the good chemical alloy homogeneity; and (4) the mechanical properties improvement of re-crystallized grains with a coherent structure. The crystallographic lattice of both alloys results in FCC. The Zr-modified HEA presents a higher recrystallization temperature and smaller grain size after recrystallization with respect to the Cantor’s alloy, with precipitation of a coherent second phase, which enhances the alloy hardness and strength.

Highlights

The first scientific papers on High Entropy Alloys (HEAs) were published in 2004 [1]
Raw materials are cold rolled and annealed. recrystallization occurred during the heat treatment of the cold-rolled HEA
The unique properties of the HEAs are ascribed to the inherent properties of a multicomponent solid solution, such as a distorted lattice structure [10], cocktail effect [11], sluggish diffusion [4] and nano-scale twinning [8]

Summary

Introduction

The first scientific papers on High Entropy Alloys (HEAs) were published in 2004 [1]. Based on previous studies on Mn-free CoCrFeNiZrx (0.1 ≤ x ≤ 0.5) [35], Zr is expected to bring about recrystallization after cold de-formation and to originate a fine-grained micro-structure Owing due to these considerations, in this work both, equimolar and Zr-added Cantor’s alloys were produced with an alternative melting process, starting from pre-alloyed powders of CrNiFeCoMn mixed by mechanical alloying. The main advantages of this approach with respect to the traditional techniques are the reduced time for the vacuum induction melting (VIM) process due to eutectic formation between Zr and all elements used in the Cantor’s alloy and the satisfactory chemical homogeneity obtained in a shorter time thanks to the use of pre-alloyed powders. The micro-structure and recrystallization processes of the Co20Cr20Fe20Mn20Ni20 and Co19Cr19Ni19Fe19Mn19Zr5 are described

Materials and Methods

Conclusions