Supplementary information

Superior tensile properties of 1%C-CoCrFeMnNi high-entropy alloy

additively manufactured by selective laser melting

Jeong Min Parka, Jungho Choeb, Jung Gi Kima,c, Jae Wung Baea, Jongun

Moona, Sangsun Yangb, Kyung Tae Kimb, Ji-Hun Yub,d, Hyoung Seop

Kima*

aDepartment of Materials Science and Engineering, Pohang University of Science and

Technology, Pohang 37673, Republic of KoreabPowder & Ceramic Division, Korea Institute of Materials Science (KIMS), Changwon

51508, Republic of KoreacMax-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straβe 1, Dusseldorf

40237, GermanydMetal 3D Printing Convergence Research Team, Korean Institute of Machinery &

Materials (KIMM), Daejeon 34103, Republic of Korea

*Corresponding author (Hyoung Seop Kim): Tel.: +82 54 279 2150; E-mail:

hskim@postech.ac.kr

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Powder characterization

The particle size distribution of the (CoCrFeMnNi)99C1 (at%) HEA powders used in the

present SLM process was estimated using laser diffraction particle size analyzer (LS 13 320,

Beckman Coulter). Figure S1 showed the SEM micrograph and the size distribution of the C-

HEA powders. Most of the particles exhibited nearly spherical shape (Fig. S1a), and the

measured particle diameters at 10%, 50%, and 90% in the cumulative distribution (Fig. S1b)

were 14.41 μm (d10), 23.74 μm (d50), and 39.08 μm (d90), respectively. As shown in Fig. S2, the

XRD pattern of the present C-HEA powders clearly showed FCC structure. The determination

of oxygen and nitrogen contents in the powders was also carried out using an O/N determinator

(ON-900, ELTRA Ltd.), and the measured O and N contents were 529.2 ppm and 307.1 ppm,

respectively. To evaluate the flowability of the powders which affects powder packing behavior

in the SLM process, Hausner ratio was estimated from the tap density and apparent density.

Furthermore, the time required for the flow of 50 g of powder (Hall flow rate) was also

measured using Hall Flowmeter funnel. Table S1 presented the result of these evaluations,

implying good flowability of the C-HEA powders for the SLM process.

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SLM-processed CoCrFeMnNi HEAs

The powder of CoCrFeMnNi HEAs without carbon addition was also prepared for the

SLM process in the same methods. The rectangular blocks (30×6×6 mm3) were built from the

CoCrFeMnNi powder using the SLM process of the same scanning strategy for C-HEAs (as

described in Fig. 1a in the manuscript) under the two laser scanning-speeds: 200 and 600 mm s-1

(labeled HEA-V200 and HEA-V600, respectively). As shown in Fig. S5, the CoCrFeMnNi

HEAs were successfully fabricated using the SLM process, and the resulting mean grain size on

the Z plane of HEA-V200 and –V600 are measured to be ~28.3 μm and ~14.5 μm, respectively.

Table S3 presents the tensile properties of the HEA-V200 and –V600 samples. It is noted that

the as-built CoCrFeMnNi HEAs (without carbon addition) exhibited much lower strength levels

(nearly ~200 MPa decreased) than the SLM-processed 1%C-CoCrFeMnNi HEAs. From Eq. (2)

in the present study, the interstitial solid solution effect (σ c = ~78 MPa) by carbon content and

the carbide strengthening (∆ σ ppt) could be ignored to describe the contribution of strengthening

mechanisms for the yield strength of the as-built CoCrFeMnNi HEAs. Also, from the mean

grain sizes of HEA-V200 and –V600 samples, the calculated yield strengths are ~584 and ~557

MPa, respectively. It also showed good consistency with the experimental results as indicated in

Table S3.

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Supplementary figures

Figure S1. (a) SEM micrograph of the C-HEA powder, and (b) particle size distribution of

powders.

Figure S2. XRD pattern of the gas atomized (CoCrFeMnNi)99C1 (at%) powder.

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Figure S3. KAM distribution profiles of the EBSD maps for (a) C-HEA-V200 and (b) -

V600 samples.

Figure S4. STEM micrographs of the C-HEA-V600 sample: (a) Bright-field image and

(b) Dark-field image with nano-precipitates highlighted using yellow arrows.

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Figure S5. Microstructure of the SLM-processed CoCrFeMnNi HEAs: 3D IPF maps

for (a) HEA-V200 and (b) –V600 samples.

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Supplementary tables

Table S1. Physical properties of the (CoCrFeMnNi)99C1 (at%) powders.

Apparent density Tap density Hausner ratio Hall flow rate4.23±0.02 g∙cm-3 4.60±0.08 g∙cm-3 1.09 15.20±0.19 sec/50g

Table S2. The fraction of HAGBs and LAGBs of the as-built C-HEAs.

SamplesFraction of GBs

LAGBs HAGBs

C-HEA-V200 0.68 0.32

C-HEA-V600 0.55 0.45

Table S3. Tensile properties of the SLM-processed CoCrFeMnNi HEAs.

Sample Yield Strength Tensile Strength Total ElongationHEA-V200 ~614 MPa ~705 MPa ~22.4%HEA-V600 ~564 MPa ~687 MPa ~31.0%

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