Rapid Solidification Behavior and Microstructure Regulation of Ni43.5Co19Cr10Fe10Al15Ti2Mo0.5 Eutectic High-Entropy Alloy

doi:10.11900/0412.1961.2024.00271

Acta Metall Sin

2025, Vol. 61

Issue (1): 191-202 DOI: 10.11900/0412.1961.2024.00271

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Rapid Solidification Behavior and Microstructure Regulation of Ni_43.5Co₁₉Cr₁₀Fe₁₀Al₁₅Ti₂Mo_0.5 Eutectic High-Entropy Alloy

LU Jianlin, REN Huayong, XIE An, WANG Jiantong, HE Feng(

)

State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China

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LU Jianlin, REN Huayong, XIE An, WANG Jiantong, HE Feng. Rapid Solidification Behavior and Microstructure Regulation of Ni_43.5Co₁₉Cr₁₀Fe₁₀Al₁₅Ti₂Mo_0.5 Eutectic High-Entropy Alloy. Acta Metall Sin, 2025, 61(1): 191-202.

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Abstract

Eutectic high-entropy alloys (EHEAs) have exhibited excellent mechanical properties. However, their rapid solidification behaviors during additive manufacturing processes still require further investigation. In the present study, Ni_43.5Co₁₉Cr₁₀Fe₁₀Al₁₅Ti₂Mo_0.5 EHEA via copper mold casting and selective laser melting (SLM) were produced to study the influence of solidification conditions, such as cooling rate, on the phase area fraction, phase composition, grain morphology, and mechanical properties of the alloy. SEM, EBSD, TEM, and tensile testing were used to systematically analyze the solidification behaviors and mechanical properties of this EHEA. The center of the as-cast specimen has the lowest cooling rate, a large amount of fcc primary phase appears and forms equiaxed crystals, with a B2 phase area fraction of 16.9%. As the cooling rate increases, the amount of fcc primary phase decreases, and the area fraction of the B2 phase increases to 23.0% on the surface of the as-cast specimen. Meanwhile, the concentration of Al in the B2 phase of each region in the as-cast specimen is 23.2% (atomic fraction, the same below). However, with the continuous increase in the cooling rate, the area fraction of B2 phase tends to reach its lowest value in the SLM specimen, with only 15.8% in edge-on orientation, and the concentration of Al in the B2 phase decreases to 16.5%. The decrease in the area fraction of the B2 phase in SLM samples is due to solute trapping caused by the high cooling rate, resulting in the formation of a supersaturated solid solution and a reduction in the amount of liquid phase available for forming eutecticphase. In addition, during the SLM process, a high scanning rate results in a large temperature gradient, which promotes the formation of columnar crystals. Reducing the scanning rate to 500 mm/s causes a columnar-to-equiaxed transition due to the decrease in temperature gradient. The mechanical properties of the SLM specimens are superior to those of the as-cast specimens, with a room-temperature ultimate tensile strength of (1320.5 ± 4.5) MPa and a fracture elongation of (25.8 ± 2.2)%.

Key words: eutectic high-entropy alloy rapid solidification selective laser melting

Received: 14 August 2024

ZTFLH:

TG146.1

Fund: National Natural Science Foundation of China(52474425)

Corresponding Authors: HE Feng, professor, Tel: 18710790457, E-mail: fenghe1991@nwpu.edu.cn

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	LU Jianlin
	REN Huayong
	XIE An
	WANG Jiantong
	HE Feng

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https://www.ams.org.cn/EN/10.11900/0412.1961.2024.00271 OR https://www.ams.org.cn/EN/Y2025/V61/I1/191

Fig.1 XRD spectrum of the as-cast powder specimen

Fig.2 Low (a-c) and high (d-f) magnified OM images and EBSD phase distribution (PD) images (g-i) of different regions on as-cast specimen cross-section
(a, d, g) chill crystal zones (b, e, h) columnar zones (c, f, i) equiaxed grain zones

Fig.3 SEM images (a, d, g) and EDS analyses (b, c, e, f, h, i) of different crystal zones of the as-cast specimen (Arrows in Fig.3a, b, d, e, g, and h show the EDS line scanming directions)
(a, b, c) chill crystal zones (d, e, f) columnar zones (g, h, i) equiaxed grain zones

Fig.4 XRD spectra of the powder raw material (a) and SLM-C as-print specimen (b)

Fig.5 OM (a, b) and SEM (d, e) images and inverse pole figures (IPFs) (c, f) of the SLM-C as-print specimen (Orange areas in the cubes indicate the observation plane, the same below)

Fig.6 TEM images (a, f), selected area electron diffraction (SAED) patterns (b-d), and EDS analyses (e, g, h) of the as-print SLM-C specimen along the cross-section perpendicular to the additive direction
(d) Kurdjumov-Sachs (K-S) relation between B2 and fcc phases
(e) EDS line scanning result (g, h) EDS mappings of Al (g) and Ti (h)

Fig.7 Engineering strain-stress curves of the as-print SLM-C specimen and columnar and equiaxed grain zones of the as-cast specimen (g represents the direction of gravity. Insets are the sampling position schematics, where black and blue areas represent the sampling positions of the columnar and equiaxed grain zones in as-cast specimen, respectively; and two layers close to the upper surface represent the sampling position of as-print specimen)

Fig.8 IPF (a) and SEM image (b) of the SLM-E as print specimen and relationships between the columnar to equiaxed transition (CET) and the printing parameters in SLM-E as-print specimens (c-f)

Fig.9 Low (a) and high (b) magnified OM images of shrinkage cavity in the middle of the as-cast specimen

Fig.10 Engineering strain-stress curves (a) and OM image (b) of SLM-E as-print specimen and kernel average misorientation (KAM) images of SLM-C (c) and SLM-E (d) as-print specimens (Inset in Fig.10a is the sampling position schematic of SLM-E, where two layers close to the upper surface represent the sampling position)

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