The Temperature Dependence of Deformation Behaviors in High-Entropy Alloys: A Review

Over the past seventeen years, deformation behaviors of various types of high-entropy alloys (HEAs) have been investigated within a wide temperature range, from cryogenic to high temperatures, to demonstrate the excellent performance of HEAs under extreme conditions. It has been suggested that the dominated deformation mechanisms in HEAs would be varied with respect to the environmental temperatures, which significantly alters the mechanical properties. In this article, we systematically review the temperature-dependent mechanical behaviors, as well as the corresponding mechanisms of various types of HEAs, aiming to provide a comprehensive and up-to-date understanding of the recent progress achieved on this subject. More specifically, we summarize the deformation behaviors and microscale mechanisms of single-phase HEAs, metastable HEAs, precipitates-hardened HEAs and multiphase HEAs, at cryogenic, room and elevated temperatures. The possible strategies for strengthening and toughening HEAs at different temperatures are also discussed to provide new insights for further alloy development.

Download Full-text

High-entropy alloys in light transition metal systems

Acta Crystallographica Section A Foundations and Advances ◽

10.1107/s2053273314090561 ◽

2014 ◽

Vol 70 (a1) ◽

pp. C943-C943

Author(s):

Roksolana Kozak ◽

Walter Steurer

Keyword(s):

Single Phase ◽

Elevated Temperatures ◽

High Hardness ◽

High Entropy Alloys ◽

X Ray Diffraction ◽

High Entropy ◽

Mixing Entropy ◽

Al Content ◽

New Class ◽

Arc Melting

High-entropy alloys (HEAs) are a new class of alloys designed with the approach of maximization of configurational mixing entropy by increasing the number of constituents [1,2]. Alloys produced in such a way are reported for a variety of promising properties (high hardness and strength, wear resistance, magnetism etc.) [3]. However, origin of these properties (microstructure, phase content, element composition, thermal history) is not always clear. High mixing entropy in HEAs favours the formation of single-phase substitutional solid solutions at elevated temperatures with approximately equiatomic compositions and simple average crystal structures of either the cF4-Cu (fcc) or the cI2-W (bcc). Nevertheless, only a few element combinations produce truly single-phase materials. In order to search for new HEAs compositions samples in the systems Cr-Fe-Co-Ni-Al and Cr-Fe-Co-Ni-Mn were synthesized by arc melting and homogenized in tantalum ampoules at 1100 and 1300 °C for 2 weeks. DTA, X-ray diffraction and electron microscopy measurements were performed. Only samples with small Al content (~ 5 at.%) showed the single-phase microstructure. Their local atomic structure is under investigation.

Download Full-text

Development of Precipitation-Strengthened Al0.8NbTiVM (M = Co, Ni) Light-Weight Refractory High-Entropy Alloys

Materials ◽

10.3390/ma14082085 ◽

2021 ◽

Vol 14 (8) ◽

pp. 2085

Author(s):

Kangjin Lee ◽

Yunjong Jung ◽

Junhee Han ◽

Sung Hwan Hong ◽

Ki Buem Kim ◽

...

Keyword(s):

Mechanical Properties ◽

Yield Strength ◽

Single Phase ◽

Elevated Temperatures ◽

Critical Role ◽

Mixing Enthalpy ◽

Homogeneous Distribution ◽

High Entropy Alloys ◽

Light Weight ◽

High Entropy

Single-phase solid-solution refractory high-entropy alloys (RHEAs) have been receiving significant attention due to their excellent mechanical properties and phase stability at elevated temperatures. Recently, many studies have been reported regarding the precipitation-enhanced alloy design strategy to further improve the mechanical properties of RHEAs at elevated temperatures. In this study, we attempted to develop precipitation-hardened light-weight RHEAs via addition of Ni or Co into Al0.8NbTiV HEA. The added elements were selected due to their smaller atomic radius and larger mixing enthalpy, which is known to stimulate the formation of precipitates. The addition of the Ni or Co leads to the formation of the sigma precipitates with homogeneous distribution. The formation and homogeneous distribution of sigma particles plays a critical role in improvement of yield strength. Furthermore, the Al0.8NbTiVM0.2 (M = Co, Ni) HEAs show excellent specific yield strength compared to single-phase AlNbTiV and NbTiVZr RHEA alloys and conventional Ni-based superalloy (Inconel 718) at elevated temperatures.

Download Full-text

A review on phase prediction in high entropy alloys

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/09544062211008935 ◽

2021 ◽

pp. 095440622110089

Author(s):

Vinay Kumar Soni ◽

S Sanyal ◽

K Raja Rao ◽

Sudip K Sinha

Keyword(s):

Solid Solution ◽

Phase Formation ◽

Single Phase ◽

High Entropy Alloy ◽

High Entropy Alloys ◽

Modeling Tools ◽

High Entropy ◽

Recent Developments ◽

Phase Prediction ◽

The Stability

The formation of single phase solid solution in High Entropy Alloys (HEAs) is essential for the properties of the alloys therefore, numerous approach were proposed by many researchers to predict the stability of single phase solid solution in High Entropy Alloy. The present review examines some of the recent developments while using computational intelligence techniques such as parametric approach, CALPHAD, Machine Learning etc. for prediction of various phase formation in multicomponent high entropy alloys. A detail study of this data-driven approaches pertaining to the understanding of structural and phase formation behaviour of a new class of compositionally complex alloys is done in the present investigation. The advantages and drawbacks of the various computational are also discussed. Finally, this review aims at understanding several computational modeling tools complying the thermodynamic criteria for phase formation of novel HEAs which could possibly deliver superior mechanical properties keeping an aim at advanced engineering applications.

Download Full-text

Al, Cu and Zr Addition to High Entropy Alloys: The Effect on Recrystallization Temperature

Materials Science Forum ◽

10.4028/www.scientific.net/msf.941.1137 ◽

2018 ◽

Vol 941 ◽

pp. 1137-1142

Author(s):

Elena Colombini ◽

Andrea Garzoni ◽

Roberto Giovanardi ◽

Paolo Veronesi ◽

Angelo Casagrande

Keyword(s):

Solid Solution ◽

Grain Size ◽

Single Phase ◽

Boundary Energy ◽

Cold Deformation ◽

Recrystallization Temperature ◽

High Entropy Alloys ◽

High Entropy ◽

Ni Alloy ◽

Sluggish Diffusion

The equimolar Cr, Mn, Fe, Co and Ni alloy, first produced in 2004, was unexpectedly found to be single-phase. Consequently, a new concept of materials was developed: high entropy alloys (HEA) forming a single solid-solution with a near equiatomic composition of the constituting elements. In this study, an equimolar CoCrFeMnNi HEA was modified by the addition of 5 at% of either Al, Cu or Zr. The cold-rolled alloys were annealed for 30 minutes at high temperature to investigate the recrystallization kinetics. The evolution of the grain boundary and the grain size were investigated, from the as-cast to the recrystallized state. Results show that the recrystallized single phase FCC structures exhibits different twin grains density, grain size and recrystallization temperatures as a function of the at.% of modifier alloying elements added. In comparison to the equimolar CoCrFeMnNi, the addition of modifier elements increases significantly the recrystallization temperature after cold deformation. The sluggish diffusion (typical of HEA alloys), the presence of a solute in solid solution as well as the low twin boundary energy are responsible for the lower driving force for recrystallization.

Download Full-text

Accelerated discovery of single-phase refractory high entropy alloys assisted by machine learning

Computational Materials Science ◽

10.1016/j.commatsci.2021.110723 ◽

2021 ◽

Vol 199 ◽

pp. 110723

Author(s):

Yonggang Yan ◽

Dan Lu ◽

Kun Wang

Keyword(s):

Machine Learning ◽

Single Phase ◽

High Entropy Alloys ◽

High Entropy

Download Full-text

Study on properties of single-phase high entropy alloys with FCC structure based on the empirical electron theory

Journal of Alloys and Compounds ◽

10.1016/j.jallcom.2021.162892 ◽

2021 ◽

pp. 162892

Author(s):

Xinpeng Guo ◽

Yongquan Guo ◽

Linhan Yin

Keyword(s):

Single Phase ◽

High Entropy Alloys ◽

Electron Theory ◽

High Entropy ◽

Empirical Electron Theory ◽

Fcc Structure

Download Full-text

Shear localization of fcc high-entropy alloys

EPJ Web of Conferences ◽

10.1051/epjconf/201818303028 ◽

2018 ◽

Vol 183 ◽

pp. 03028 ◽

Cited By ~ 1

Author(s):

Marc A. Meyers ◽

Zezhou Li ◽

Shiteng Zhao ◽

Bingfeng Wang ◽

Yong Liu ◽

...

Keyword(s):

Shear Strain ◽

Single Phase ◽

Dynamic Compression ◽

Impact Resistance ◽

Shear Localization ◽

Solid Solution Hardening ◽

High Entropy Alloys ◽

High Entropy ◽

Work Hardening Rate ◽

High Work

Dynamic behavior of the single phase (fcc) Al0.3CoCrFeNi and CoCrFeMnNi high-entropy alloys (HEAs) was examined. The combination of multiple strengthening mechanisms such as solid solution hardening, cutting forest dislocation, as well as mechanical nano-twinning leads to a high work-hardening rate, compared with conventional alloys. The resistance to shear localization was studied by dynamicallyloading hat-shaped specimens to induce forced shear localization. However, no adiabatic shear band could be observed for Al0.3CoCrFeNi HEA at a large shear strain ~1.1. Additionally, shear localization of the CoCrFeMnNi HEA was only found at an even larger shear strain ~7 under dynamic compression. It is therefore proposed that the combination of the excellent strain-hardening ability and modest thermal softening of these two kinds of high-entropy alloys gives rise to remarkable resistance to shear localization, which makes HEAs excellent candidates for impact resistance applications.

Download Full-text