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Design of a novel (CoCrNi)84.5Al15.5 eutectic medium-entropy alloy with hierarchically nano-lamellar microstructure through additively manufactured compositionally graded materials
Mengyao Zhenga , Chuanwei Lia,b,*, Xinyu Zhanga, Zhenhua Yea, Yu Liaoa, Jianfeng Gua,c, *
a insinte of Materials Modifcaton and Modeling, School of Materals Science and Engineering, Shanghai jiao Tong Uniersily, Shanghai, 200240, China
bShanghai Key Labaratory of Materials Laser Processing and Modiicatior, Shanghai Jiao Tong Univrsily, Shangha, 200240, china
cMaterials Genowe Iririative Center, Shanghai Jiao Tong liiversity, shanghai, 200240, China
Abstract:
Eutectic medium/high-entropy alloys (E-M/HEAs) exhibit excellent castability and mechanical properties, Thispresent work developed a novel CoCrNiAl based E-MEAs through a high-throughput method based on compositionally graded materials by laser directed energy deposition. The microstructure in the GoCrNiAlx (x ≈ 0 -0.8)compositionally graded alloy changed from columnar to equiaxed with increasing Al content, and the fraction ofbody-centered cubic (BCC) phase increased simultaneously. Especially, a eutectic lamellar microstructure withface-centered cubie (FCC) and ordered BCc (B2) was obtained when the Al content reached 15.5 at%, and itshowed a better strength.-ductility combination than other reported cast eutectic alloys. The mechanical-propertyimprovement of this novel E-MEA is related to its hierarchically nano-lamellar microstructure, in which theorientation relationship (OR) between FCC and B2 lamellae conforms to the Kurdjumov-Sachs OR, and sphericalBCC and ordered FCC phases precipitate from B2 and FCC lamellae, respectively. Furthermore, the fracturemechanisms of this novel E-MEA were also investigated by in-situ tensile test and transmission electron mi.croscope, indicating that the crack modes were closely related to the eutectic lamellar direction relative to thetensile axis, and the considerable ductility stemmed from the cooperative deformation between FCC and B2 phases caused Deformation mechanisms.
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