Atomic Mechanism of Plastic Deformation for Poly-crystalline CoNiCrFeMn High Entropy Alloy
HUANG Weiling1, CHEN Jingjing2
1 Mechanical and Electrical Engineering Department, Gannan University of Science and Technology, Ganzhou 341000, China 2 School of Physics and Electrical Engineering, Ningde Normal University, Ningde 352100, China
Abstract: CoNiCrFeMn high-entropy alloy plays an extremely significant role in national major fields such as deep-sea detection in lower temperature, supersonic engine and space ultrasonic motor due to its excellent properties of high strength and toughness, wear resistance, corrosion resistance, high temperature softening and low temperature resistance. Therefore, it is of great significance to research its evolution process of plastic deformation. This work focused on the basic research of the correlation characteristic for CoNiCrFeMn high-entropy alloy between load versus depth curve and micro-structural evolution, and the mechanism features of its plastic defor-mation was revealed. It was noted that the amorphous phase transition and dislocation nucleation appeared simultaneously after elastic deformation, and then increase gradually as indentation depth increases. Furthermore, an interesting phenomenon of dislocation slip can be discovered in grain, which was expected to the stress concentration induced from local contact area. At the same time, the grain boundary prevents dislocation slip. As amorphous phase transition reached the grain boundary, it will not continue. Instead, the local stress concentration was released in adjacent grains with a form of dislocation emission, so that the grain boundary becomes the source of dislocation emission. On the other hand, this report showed that the load versus depth curve during elastic stage was not sensitive to temperature changes at room temperature 300 K or below, while the load at plastic stage decreases gradually with temperature increasing. Moreover, the fluctuation degree on upper surface of poly-crystalline high-entropy alloy became serious and presented heterogeneity on the both sides of local contact area due to increasing temperature. This research will provide insight on response of the micro-structure evolution induced by loading for poly-crystalline high-entropy alloy at atomic scale, which shows an important academic value on deep exploration into the plastic deformation mechanism for poly-crystalline high-entropy alloys, and provides a reference value on improving their structure and mechanical properties.
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2021, Vol. 35 
