Superior strength-ductility synergy in additively manufactured CoCrFeNi high-entropy alloys with multi-scale hierarchical microstructure

• Published in: Journal of alloys and compounds Vol. 1006; p. 176268
• Main Authors: Wang, Shanshan, Chen, Zhe, Chen, Ruiguang, Wu, Zhining, Jia, Yunfeng, Zhang, Weijian, Wang, Yixiang, Liu, Weihong, Zhao, Yilu, Shi, Rongpei, Cao, Boxuan, Yu, Suzhu, Wei, Jun
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 25.11.2024
• Subjects: Additive manufacturing; Columnar grains; Hierarchical structure; High-entropy alloy; Mechanical properties; Microstructure; Mechanical properties; Columnar grains; Additive manufacturing; Microstructure; High-entropy alloy; Hierarchical structure
• ISSN: 0925-8388
• DOI: 10.1016/j.jallcom.2024.176268

Additive manufacturing offers a feasible route for fabricating net-shape metallic materials with advanced physicochemical and mechanical properties, which is unattainable through conventional routes. This study focuses on the processing parameters, microstructural, and mechanical properties of the CoCrFeNi high-entropy alloys (HEAs) fabricated via laser powder bed fusion (LPBF). A near-dense LPBF CoCrFeNi HEA was manufactured by fine-tuning the parameters. Compared with conventionally processed CoCrFeNi HEAs, the as-built samples exhibit excellent strength-ductility synergy with 200 % higher yield strength and unsacrificed ductility. Microstructural analyses of the LPBF samples demonstrate a hierarchical structure including melt pools, columnar grains, dislocation cells, and elemental segregations. This excellent strength is attributed to the high-density dislocation cellular structure and Cr2O3 nanoparticles that impede the dislocation motion. The excellent ductility correlates to the steady work-hardening regulated by the interactions between cellular structure, dislocations, deformation twins, and nanoprecipitation. This work provides promising outlook towards fabricating high-performance alloys with tailored hierarchical microstructure. •The as-printed CoCrFeNi HEAs demonstrated hierarchical structure characteristics.•The as-printed CoCrFeNi HEAs demonstrated a yield strength over 550 MPa and ductility over 50 %.•Upon plastic deformation, the formation of Lomer-Cottrell locks served as Frank-Read dislocation source for dislocation multiplication.