MECHANICAL CHARACTERIZATION AND DEFORMATION MECHANISM OF TWINNED FeNiCrCoCu HIGH-ENTROPY ALLOY
Mechanical characteristics of twinned FeNiCrCoCu high-entropy alloy (HEA) under the nanoindentation are revealed through molecular dynamics simulation. The effect of twinning spacing on the plastic deformation behavior and crystal structure evolution are cautiously investigated. The results show that the indentation force and hardness values increase with decreasing the twinning spacing, which reveals the Hall-Petch relationship in the correlation between the material strength and twinning spacing. The deformation behavior suggests that the shear strain extends deep into the substrate along the twinning, which is shown by the shear bands. Besides, the twinning boundary plays a significant role in the plastic deformation mechanism of twined FeNiCrCoCu HEA, and the evolution of the planar defect and dislocation loop moving along the twinning. The result also shows that the Shockley dislocation accounts for a large proportion of total dislocations formed during the indentation for all specimens. Moreover, the dislocation density increases quickly during the loading phase, and then decreases rapidly during the unloading phase. Finally, the surface morphology shows that the largest pile-up height is for twinning spacings of 20.4 Å and 80.0 Å, while the smallest pile-up height is for twinning spacing of 54 Å.
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