High-Temperature Strengthening and Toughening Behavior and Associated Deformation Mechanism of CoCrNi-Based Medium Entropy Alloy with Rich Co and Cr Content

作者：Yan Fei; Du Xinghao^*; Jin Chengyan; Shi Chuanxin; Gai Yehui; Li Wanpeng; Tzu Hsiu Chou; Huang Chih-Ching

来源：RARE METAL MATERIALS AND ENGINEERING, 2023, 52(1): 179-185.

• CoCrNiAlTi medium entropy alloy
• strengthening phase
• high-temperature mechanical properties
• strengthening and toughening mechanism

In this work, the high temperature mechanical properties and the associated deformation mechanism of CoCrNi-based entropy alloy with rich- CoCr content were studied. It is found that the alloy with the composition of Co33.3Cr30.6Ni26.1Al5Ti5 ( at%) exhibits excellent instantaneous tensile properties in the temperature range of 600 degrees C to 800 degrees C after hot forging and aging heat treatment. In particular, the yield strength anomaly occurs at 700 degrees C, the tensile yield strength is as high as 944 MPa and the elongation at break is 16%, which is better than most nickel- base and cobalt-base superalloys. By X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope ( TEM) and three- dimensional atomic probe (3D-APT), it is found that the strong ordered strengthening of high-volume fraction multi- principal.' [(Ni, Co, Cr) 3(Al, Ti)] phase combined with grain boundary strengthening arising from the formation of fcc phase with rich-CoCr is the main factor for the excellent high temperature properties of the alloy.