Intermetallic Phases in High-Entropy Alloys: Statistical Analysis of their Prevalence and Structural Inheritance

Ming-Hung Tsai,Ting Chang,Ruei-Chi Tsai,Wen-Fei Huang

doi:10.3390/met9020247

Ming-Hung Tsai, Ting Chang + Show 2 more

Open Access

https://doi.org/10.3390/met9020247

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Abstract

Strengthening high entropy alloys (HEAs) via second phases is a very effective approach. However, the design of intermetallic (IM) phases in HEAs is challenging, mainly because our understanding of IM phases in HEAs is still very limited. Here, a statistical approach is used to enhance our understanding towards IM phases in HEAs. A database consisting of 142 IM-containing HEAs was constructed. Our aim is twofold. The first is to reveal the most common IM phase types in published HEAs. The second is to understand whether HEAs inherit their IM structures from their binary/ternary subsystems, or whether they tend to form new structures irrelevant to their subsystems. The results show that the five most prevalent IM structures in the HEAs surveyed here are Laves, σ, B2, L12, and L21. This trend is evidently different from the overall trend among known binary/ternary IMs. As for structural inheritance, all the IM phases contained in the alloys are existing structures in the binary/ternary subsystems of the respective alloys. This suggests that the compositional complexity in HEAs does trigger additional complexity in IM structure formation. These findings have important implications in the future design and development of HEAs.

Highlights

High-entropy alloys (HEAs) have attracted significant attention in the past decade [1–3].The formation of simple solid solutions (SSSs) in these complex alloys is unexpected and intriguing.a lot of effort in the HEA community has been devoted to the design and physical metallurgy of SSS HEAs [4–11]
Because the target of this research is the IM phase, each IM phase in the alloy is listed in a separate row
Compared with the top-five list in our database, it is seen that the Laves, B2, and L12 phases remain popular in HEAs, but the BaAl4 and Co2 Si structures do not appear in our HEA database at all

Summary

Introduction

High-entropy alloys (HEAs) have attracted significant attention in the past decade [1–3]. The tailoring of IM phases in HEAs for property enhancement is still very challenging This is because compared with SSS phases; our fundamental understanding of IM phases in HEAs is still very limited. A plausible assumption is that the candidate IM phases in HEAs are the IM phases in their subsystems (for quinary HEAs this means all quaternary, ternary, and binary subsystems). In HEAs a new class of IM phases called high entropy intermetallics (HEI) have been reported [21] These new IM phases show completely new compositions that have not reported before, which further complicates the determination of the candidate IM phases. IM phase types in HEAs. The results in HEAs are compared with the general trends in binary and ternary IM phases and discussed. The frequency which irrelevant (i.e., not existing in corresponding subsystems) structure types occur is probed and discussed

Construction of the Alloy Database

Characterization of the Database

The abbreviations for IM structures are

The Most Prevalent IM Structures

Structure Inheritance in HEAs

Conclusions