(Peer-Reviewed) Effect of Cu-Rich Phase Precipitation on the Microstructure and Mechanical Properties of CoCrNiCux Medium-Entropy Alloys Prepared via Laser Directed Energy Deposition
Yong Xie 谢勇 ¹, Zhixin Xia 夏志新 ¹, Jixin Hou 侯纪新 ¹, Jiachao Xu 徐加超 ², Peng Chen 陈鹏 ¹, Le Wan 万乐 ²
¹ Shagang School of Iron and Steel, Soochow University, Suzhou, 215131, China
中国 苏州 苏州大学沙钢钢铁学院
² School of Mechanical and Electric Engineering, Soochow University, Suzhou, 215131, China
中国 苏州 苏州大学机电工程学院
Abstract
To shed light into the application potential of high-entropy alloys as "interlayer" materials for Al-steel solid-state joining, we investigated the nature of the CoCrFeMnNi/Fe and CoCrFeMnNi/Al solid/solid interfaces, focusing on the bonding behavior and phase components. Good metallurgical bonding without the formation of hard and brittle IMC can be achieved for CoCrFeMnNi/Fe solid/solid interface.
In contrast to the formation of Al₅Fe₂ phase at the Fe/Al interface, Al₁₃Fe₄-type IMC, in which the Fe site is co-occupied equally by Co, Cr, Fe, Mn and Ni, dominates the CoCrFeMnNi/Al interface. Although the formation of IMC at the CoCrFeMnNi/Al interface is not avoidable, the thickness and hardness of the Al₁₃(CoCrFeMnNi)₄ phase formed at the CoCrFeMnNi/Al interface are significantly lower than the Al₅Fe₂ phase formed at the Fe/Al interface. The activation energies for the interdiffusion of Fe/Al and CoCrFeMnNi/Al static diffusion couple are 341.6 kJ/mol and 329.5 kJ/mol, respectively.
Despite this similarity, under identical static annealing condition, the interdiffusion coefficient of the CoCrFeMnNi/Al diffusion couple is significantly lower than that of the Fe/Al diffusion couple. This is thus mainly a result of the reduced atomic mobility/diffusivity caused by the compositional complexity in CoCrFeMnNi high-entropy alloy.
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