Dynamic compressive properties and microstructural evolution of Al1.19Co2CrFeNi1.81 eutectic high entropy alloy at room and cryogenic temperatures. (July 2022)

• Record Type: Journal Article
• Authors: Zhong, Xianzhe; Zhang, Qingming; Ma, Mingzhen; Xie, Jing; Wu, Mingze; Ren, Siyuan; Yan, Yongming
• Is Part Of: Materials & design. Volume 219(2022)
• Publication Date: 2022-07
• Subjects: Eutectic high entropy alloy -- Impact loading -- Deformation mechanism -- Nanotwins -- Adiabatic shear band; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2022.110724
• Languages: English
• ISSNs: 0264-1275

Abstract

Graphical abstract: Highlights: The Al1.19 Co2 CrFeNi1.81 EHEA exhibits significant strain rate effect and strain rate sensitivity. The EHEA shows an excellent strength-plasticity combination under dynamic compression loading. Cryogenic temperature can lead to an extensive strain hardening ability without embrittlement for the EHEA. The deformation mechanisms of the EHEA under dynamic loading at different temperatures are revealed. Abstract: The development of aerospace and military defense sectors has put forward higher requirements for the mechanical properties of metals under extreme conditions. Eutectic high entropy alloys (EHEAs) show a wide potential application in these fields due to their superior mechanical performances and good castability. Here, we systematically investigated the dynamic compressive properties and microstructural characteristics of the Al1.19 Co2 CrFeNi1.81 EHEA at room temperature (298 K) and liquid nitrogen temperature (77 K). The EHEA exhibits an excellent strength-plasticity combination, especially at the strain rate of 4300 s −1 at 77 K, showing a yield strength of 1365 MPa and a true plastic strain over 40%. The underlying deformation mechanisms were uncovered using transmission electron microscopy, revealing that the deformation mechanism is dominated by dislocation slip at 298 K. However, at 77 K, nanotwins together with dislocation slip dominate the plastic deformation. Meanwhile, profuse relatively stable structures are formed due to the interactions between stacking fault (SF)-SF, dislocation-twin boundary and nanotwin-nanotwin, which can effectively inhibit dislocation movement and contribute to a superior strain hardening ability. The adiabatic shear band forms in the late stage of dynamic deformation, and the fractographic observations show a transition from ductile to mixed ductile–brittle fracture mode with decreasing temperature.