Effect of Co on phase stability and mechanical behavior of CoxCrFeNiMnAl0.3 high entropy alloys with micro/nano hierarchical structure. (March 2022)

• Record Type: Journal Article
• Authors: Zhang, Guannan; Yang, Xiao; Qi, Wu; Li, Yong; Wang, Wei; Chen, Yixiang; Li, Jiangtao; Li, Laifeng
• Is Part Of: Materials & design. Volume 215(2022)
• Publication Date: 2022-03
• Subjects: High-entropy alloys -- CoxCrFeNiMnAl0.3 -- Phase stability -- Micro/nano hierarchical structure -- Mechanical behavior; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2022.110442
• Languages: English
• ISSNs: 0264-1275

Abstract

Graphical abstract: Highlights: Reducing Co content in CoCrFeNiMnAl0.3 high entropy alloys (HEAs) can effectively reduce the stability of the face-centered cubic (FCC) solid solution phase and promote the formation of the BCC (body-centered cubic) phase. The ratio of Ni equivalent and Cr equivalent (Creq /Nieq ) has been confirmed to be used to characterize the total BCC/FCC phase forming ability in Cox CrFeNiMnAl0.3 HEAs system. Reasonable control of Co content and thermo-mechanical treatment technology can result in the formation of hierarchical structure composed of micro-FCC and BCC solid solution and nano-B2 precipitation. The formed BCC phase can effectively suppress the grain growth of FCC solid solution during the recrystallization and improve the tensile strength of the alloy. Abstract: Co-Cr-Fe-Ni-Mn high entropy alloys (HEAs) have attracted extensive attention due to their broad cryogenic engineering application potential, reasonable control of alloying elements can significantly improve its mechanical performance. In this work, the effects of Co content on the phase stability and mechanical behavior Cox CrFeNiMnAl0.3 HEAs were investigated. It is found that with the decrease of the Co content, the stability of the face-centered cubic (FCC) solid solution phase in the alloy decreases, resulting in the precipitation of the BCC (body-centered cubic) phase from the FCC phase, thereby obtaining the FCC + BCC dual-phase structure. During annealing, the precipitated BCC phase can effectively suppress the grain growth and recrystallization of the FCC solid solution, forming an ultrafine-grained microstructure. In addition, the Ni-Al type nano-B2 phase can form in the BCC phase under the influence of the negative formation enthalpy during solidification. This micro/nano hierarchical structure can effectively improve the mechanical properties of the alloys. Co0.25 CrFeNiMnAl0.3 maintains relatively excellent tensile yield strength (486 MPa), the tensile elongation remains above 20 %. This study regulates the formation of the BCC phase and B2 phase by reducing the content of Co, which provides a new idea for the preparation of low-cost HEAs with excellent mechanical properties.