Tensile Response of As-Cast CoCrFeNi and CoCrFeMnNi High-Entropy Alloys

Tu-Ngoc Lam,Soo-Yeol Lee,Takuro Kawasaki,Stefanus Harjo,Mao-Yuan Luo,E-Wen Huang,Jayant Jain,An-Chou Yeh

doi:10.3390/cryst12020157

Abstract

In this research, we systematically investigated equiatomic CoCrFeNi and CoCrFeMnNi high-entropy alloys (HEAs). Both of these HEA systems are single-phase, face-centered-cubic (FCC) structures. Specifically, we examined the tensile response in as-cast quaternary CoCrFeNi and quinary CoCrFeMnNi HEAs at room temperature. Compared to CoCrFeNi HEA, the elongation of CoCrFeMnNi HEA was 14% lower, but the yield strength and ultimate tensile strength were increased by 17% and 6%, respectively. The direct real-time evolution of structural defects during uniaxial straining was acquired via in situ neutron-diffraction measurements. The dominant microstructures underlying plastic deformation mechanisms at each deformation stage in as-cast CoCrFeNi and CoCrFeMnNi HEAs were revealed using the Convolutional Multiple Whole Profile (CMWP) software for peak-profile fitting. The possible mechanisms are reported.

Highlights

High-entropy alloys (HEAs), an intriguing new class of equiatomic solid-solution alloys, have attracted interest for their promising engineering applications as structural materials [1,2,3,4]
HEA started at a stress of 194 MPa, which was a remarkable 17% increase compared to that of the CoCrFeNi HEA
HEA revealed a higher tensile strength but at the cost of lower ductility compared to the as-cast CoCrFeNi HEA

Summary

Introduction

High-entropy alloys (HEAs), an intriguing new class of equiatomic solid-solution alloys, have attracted interest for their promising engineering applications as structural materials [1,2,3,4]. The mechanical properties of FCC materials are strongly microstructure-sensitive in terms of the dislocation activities, whereby the interactions of dislocations with other defects and the dislocations strongly influence the accumulation of tensile damage under monotonic loading. The most popular FCC HEA, the Cantor alloy CoCrFeMnNi, exhibits good mechanical performance and high fatigue resistance [5,10,11,17,18,19,20]. The as-cast microstructure of the HEAs enhances fatigue resistance [21,22]. The as-cast dendritic structure is beneficial to tensile-overload-driven deformation twinning, and enhances fatigue resistance in CoCrFeMnNi HEAs [22]. Investigations of tensile-loading-governed microstructural defects in as-cast CoCrFeMnNi alloys are lacking

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