Dislocation structures below a nano-indent of the CoCrNi medium-entropy alloy

Using diffraction-contrast scanning transmission electron microscopy and molecular dynamics simulation, we study nanoindentation of a CoCrNi medium-entropy alloy. We find that the dislocation field produced can be separated into a zone of strongly entangled dislocations in the vicinity of the indenter and a zone of individual emitted loops that penetrate far from the indenter into the material interior. Comparing results obtained at 77 K and at 300 K, we observe at low temperature an increased hardness of the CoCrNi medium-entropy alloy, a higher dislocation density at the pit boundary, and more fragmented twinning boundaries indicating less twin growth. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study investigates nanoindentation behavior of a CoCrNi medium-entropy alloy using diffraction-contrast scanning transmission electron microscopy and molecular dynamics simulation. The results show that at low temperature, the alloy exhibits increased hardness, higher dislocation density at the pit boundary, and more fragmented twinning boundaries indicating reduced twin growth.