Simultaneously enhancing the ultimate strength and ductility of high-entropy alloys via short-range ordering

Zhaoxuan Wu,David J Srolovitz,Shuai Chen,Zachary H Aitken,Subrahmanyam Pattamatta,Zhi Gen Yu,Peter K Liaw,Yong-Wei Zhang

doi:10.1038/s41467-021-25264-5

Abstract

Simultaneously enhancing strength and ductility of metals and alloys has been a tremendous challenge. Here, we investigate a CoCuFeNiPd high-entropy alloy (HEA), using a combination of Monte Carlo method, molecular dynamic simulation, and density-functional theory calculation. Our results show that this HEA is energetically favorable to undergo short-range ordering (SRO), and the SRO leads to a pseudo-composite microstructure, which surprisingly enhances both the ultimate strength and ductility. The SRO-induced composite microstructure consists of three categories of clusters: face-center-cubic-preferred (FCCP) clusters, indifferent clusters, and body-center-cubic-preferred (BCCP) clusters, with the indifferent clusters playing the role of the matrix, the FCCP clusters serving as hard fillers to enhance the strength, while the BCCP clusters acting as soft fillers to increase the ductility. Our work highlights the importance of SRO in influencing the mechanical properties of HEAs and presents a fascinating route for designing HEAs to achieve superior mechanical properties.

Highlights

Enhancing strength and ductility of metals and alloys has been a tremendous challenge
Many strategies have been proposed to tailor structural heterogeneities to promote the strength-ductility synergy in HEAs8
A soft FCC lamella matrix with a hard intergranular B2 phase was designed in an AlCoCrFeNi2.1 HEA17 for the simultaneous strength-ductility enhancement

Summary

Introduction

Enhancing strength and ductility of metals and alloys has been a tremendous challenge. The SRO-induced composite microstructure consists of three categories of clusters: face-center-cubic-preferred (FCCP) clusters, indifferent clusters, and body-center-cubic-preferred (BCCP) clusters, with the indifferent clusters playing the role of the matrix, the FCCP clusters serving as hard fillers to enhance the strength, while the BCCP clusters acting as soft fillers to increase the ductility. The former exhibited a higher yield strength than the latter with comparable tensile ductility They proposed that the essential difference between these two HEAs was associated with atomic segregation and short-range ordering (SRO); both were enhanced in CoCrFeNiPd, as compared with CoCr-

Methods

Results

Conclusion