Novel Co-rich high entropy alloys with superior tensile properties

• Published in: Materials Research Letters Vol. 7; no. 2; pp. 82 - 88
• Main Authors: Wei, Daixiu, Li, Xiaoqing, Heng, Weicheng, Koizumi, Yuichiro, He, Feng, Choi, Won-Mi, Lee, Byeong-Joo, Kim, Hyoung Seop, Kato, Hidemi, Chiba, Akihiko
• Format: Report
• Language: English
• Published: Taylor & Francis 01.02.2019
• Subjects: deformation twinning; High entropy alloy; martensitic transformation; metastable; stacking fault energy
• ISSN: 2166-3831
• DOI: 10.1080/21663831.2018.1553803

We developed a series of Co-rich Co x Cr 25 (FeNi) 75−x (x = 35, 45, 55, 65) high entropy alloys with improved strength and/or ductility, derived from lowering the stacking fault energy (SFE) and reducing the fcc phase stability of the equiatomic CoCrFeNi alloy. Thermodynamics and ab initio calculations demonstrated that increasing Co while decreasing Fe and Ni concentrations lower the SFE and reduce the fcc phase stability. The Co 35 Cr 25 Fe 20 Ni 20 and Co 45 Cr 25 Fe 15 Ni 15 alloys with single fcc phase, exhibit superior tensile properties, contributing to the twinning and fcc → hcp martensitic transformation. The present study offers a guideline for designing high-performance high entropy alloys. A series of novel Co-rich non-equiatomic high entropy alloys with enhanced tensile properties were developed by lowering the stacking fault energy and reducing the phase stability of equiatomic CoCrFeNi alloy.