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

ALABD ALHAFEZ, IYAD; RUESTES, CARLOS J.; ZHAO, SHITENG; MINOR, ANDREW M.; URBASSEK, HERBERT M.

MATERIALS LETTERS

ELSEVIER SCIENCE BV

Año: 2021 vol. 283

0167-577X

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.