Selective laser melted CrMnFeCoNi + 3 wt% Y2O3 high-entropy alloy matrix nanocomposite: Fabrication, microstructure and nanoindentation properties

doi:10.1016/j.intermet.2021.107319

Intermetallics

Volume 138, November 2021, 107319

https://doi.org/10.1016/j.intermet.2021.107319 Get rights and content

Highlights

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Y₂O₃-reinforced HEA matrix nanocomposite was firstly tried to manufacture by SLM.
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SLM-nanocomposite shows heterogenous grain, dislocation networks and nano-sized Y₂O₃.
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SLM-nanocomposite reveals exceptional indentation hardness property.

Abstract

A Y₂O₃-reinforced equiatomic CrMnFeCoNi high-entropy alloy (HEA) matrix nanocomposite was fabricated by high-energy attrition milling and selective laser melting (SLM) additive manufacturing. The SLM-built HEA nanocomposite possessed heterogeneous grain structures and substructures decorated with a dislocation network and exhibited a high number density of nano-sized Y₂O₃. The SLM-built HEA + Y₂O₃ nanocomposite exhibited higher nanohardness (~9.22 GPa) than other equiatomic CrMnFeCoNi HEAs produced by casting (~4.13 GPa) and SLM (~6.95 GPa). This suggested that the dispersion hardening by the Y₂O₃ nanoparticles enabled superior mechanical properties. This study, therefore, demonstrated that Y₂O₃ reinforcement can effectively improve the mechanical properties of SLM-built CrMnFeCoNi HEA matrix nanocomposites.

Introduction

High-entropy alloys (HEAs), also referred to as compositionally complex alloys, have been intensively developed over the last decade because of their desirable physical and chemical properties [1,2]. HEAs have a unique alloy design concept that contain multiple (five or more) principal elements in equiatomic- or near-equiatomic compositions [3,4]. Among them, the equiatomic CrMnFeCoNi HEA has been extensively explored because of its excellent strength–ductility balance, corrosion resistance, fracture toughness, and resistance to hydrogen embrittlement [5,6]. However, the equiatomic CrMnFeCoNi HEA exhibits low yield strength at room temperature, which limits its application as a structural part [7]. Therefore, strategies to improve the yield strength of equiatomic CrMnFeCoNi HEAs have been developed (e.g., interstitial and oxide dispersion-strengthened HEA [8,9]). In particular, researchers have been attempting to fabricate ceramic-particle-reinforced HEA matrix nanocomposites as an alternative to high-performance structural materials.

However, the manufacturing process of HEAs is somewhat complicated. In particular, the control of nanoparticle-reinforced HEA matrix composites with compositional homogeneity is difficult to achieve in traditional manufacturing processes. Therefore, the selective laser melting (SLM) technology, which is based on the laser-powder-bed-fusion-type additive manufacturing (AM) that can fabricate a “net-shape” part, has been considered for the manufacturing of HEA matrix nanocomposites [10]. It should be noted that the SLM technology facilitates high performance in the as-built state. Y₂O₃ is one of the most promising candidates among ceramic-based dispersion reinforcements for an austenite matrix because of its excellent thermophysical and chemical stability within the molten austenitic matrix [11]. However, to date, the microstructure and mechanical properties of SLM-built Y₂O₃-nanoparticle-reinforced HEA matrix composites have not been explored. Therefore, this study investigated the fabrication, microstructure, and mechanical properties of SLM-built HEA nanocomposites.

Section snippets

Materials and methods

Pre-alloyed equiatomic CrMnFeCoNi HEA powders with a size of 15–45 μm and high-purity Y₂O₃ nano-powders with an average size of 50 nm were used as starting materials. The mixed feedstocks were mechanically alloyed using a high-energy attrition mill. Stainless steel balls with a size of 5 mm were employed as milling media with a ball-to-powder mass ratio of 10:1. To avoid agglomeration and cold-welding of the powder during mechanical alloying, 3 wt% stearic acid (CH₃(CH2)₁₆COOH) was added as a

Results and discussion

Fig. 2 shows the microstructures of the SLM-built Y₂O₃-reinforced CrMnFeCoNi HEA matrix nanocomposite (hereafter referred to as SLM-nanocomposite). The EDS elemental distribution maps corresponding to the identical regions of the SEM image revealed the uniform distribution of Co–Cr–Fe–Mn–Ni–Y–O elements in the as-built HEA nanocomposite (Fig. 2a). This behavior is a result of the fast solidification during SLM. Wang et al. [12] reported that micro-segregation can be reduced by increasing the

Conclusion

A Y₂O₃-reinforced CrMnFeCoNi HEA nanocomposite was successfully manufactured by high-energy attrition milling and SLM. The SLM-nanocomposite showed uniform elemental distribution and possessed heterogeneous grain structures with highly serrated GBs. In addition, substructures decorated with dislocation networks were formed within the grains, and large amounts of Y₂O₃ nanoparticles with an average size of 65.8 nm were observed at the sub-structure boundaries. The SLM-nanocomposite exhibited

CRediT authorship contribution statement

Young-Kyun Kim: Conceptualization, Data curation, Formal analysis, Investigation, Writing – original draft. Ji-Eun Ahn: Investigation, Data curation. Yongwook Song: Investigation. Hyunjoo Choi: Investigation. Sangsun Yang: Investigation, Project administration. Kee-Ahn Lee: Supervision, Conceptualization, Project administration, Funding acquisition, Writing – review & editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

This study supported by National Research Foundation of Korea (NRF) grant funded by the Korea government (MEST) (No. 2019R1A2C1008904).

References (16)

B. Cantor et al.
Microstructural development in equiatomic multicomponent alloys
Mater. Sci. Eng. A
(2004)
Y. Zhang et al.
Microstructures and properties of high-entropy alloys
Prog. Mater. Sci.
(2014)
E.P. George et al.
High entropy alloys: a focused review of mechanical properties and deformation mechanisms
Acta Mater.
(2020)
Y.-K. Kim et al.
High-cycle fatigue and tensile deformation behaviors of coarse-grained equiatomic CoCrFeMnNi high entropy alloy and unexpected hardening behavior during cyclic loading
Intermetallics
(2019)
Z. Li
Interstitial equiatomic CoCrFeMnNi high-entropy alloys: carbon content, microstructure, and compositional homogeneity effects on deformation behavior
Acta Mater.
(2019)
H. Hadraba et al.
Oxide dispersion strengthened CoCrFeNiMn high-entropy alloy
Mater. Sci. Eng. A
(2017)
Y.-K. Kim et al.
Compressive creep behavior of selective laser melted CoCrFeMnNi high-entropy alloy strengthened by in-situ formation of nano-oxides
Addit. Manuf.
(2020)
J.-H. Gwon et al.
Effects of cryomilling on the microstructures and high temperature mechanical properties of oxide dispersion strengthened steel
J. Nucl. Mater.
(2015)

There are more references available in the full text version of this article.

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Selective laser melted CrMnFeCoNi + 3 wt% Y2O3 high-entropy alloy matrix nanocomposite: Fabrication, microstructure and nanoindentation properties

Highlights

Abstract

Introduction

Section snippets

Materials and methods

Results and discussion

Conclusion

CRediT authorship contribution statement

Declaration of competing interest

Acknowledgement

Mater. Sci. Eng. A

Prog. Mater. Sci.

Acta Mater.

Intermetallics

Acta Mater.

Mater. Sci. Eng. A

Addit. Manuf.

J. Nucl. Mater.

Selective laser melted CrMnFeCoNi + 3 wt% Y₂O₃ high-entropy alloy matrix nanocomposite: Fabrication, microstructure and nanoindentation properties