How to improve plasticity and toughness of materials while improving strength has always been one of the hotspots in the field of material scie-nce, which is also a major scientific problem in the field of materials and an important bottleneck restricting the development of materials. The CrCoNi medium entropy alloy has excellent strength and plasticity at room temperature and low temperature, especially at liquid nitrogen tempera-ture, which attracts the attention of researchers. In the early stage of deformation, the traditional metal is mainly dislocation slip. With the increase of strain, twins are induced, and the coordi-nated deformation of twins and dislocations is realized. Unlike conventional metals, the CrCoNi medium entropy alloy has very low stacking fault energy, it is easy to form a large number of stacking faults, dislocations and twins in the deformation process. Nano-twins are introduced to refine grains in the deformation, and the coordinated improvement of strength and toughness is realized through fine grain strengthening. Moreover, twins can form three-dimensional network and improve the ability of coordinated deformation. In addition,during the deformation process of CrCoNi alloy, there is an interaction between dislocations and twins. After dislocation packing, twins are triggered, which hinders the movement of dislo-cations and improves the dislocation density. The dislocation slip channel is adjusted to promote dislocation cross slip. Thus, the plastic deforma-tion of CrCoNi alloy is more uniform and the contradiction between strength and toughness is coordinated. In order to explain the relationship between excellent mechanical properties and nano-structure of CrCoNi medium entropy alloy during deforma-tion, this paper starts from the deformation mechanism of CrCoNi medium entropy alloy, summarizes the existing morphology, motion mode and coordination mechanism of dislocation and twin in the deformation process of CrCoNi alloy, analyzes the interaction between dislocation and twin in CrCoNi alloy under different deformation conditions and their influence on deformation, and discusses the dominant mechanism of dislocation-twin synergistic strengthening and toughening. Finally, future research of medium entropy alloy is prospected. © 2022 Cailiao Daobaoshe/ Materials Review. All rights reserved.
