Dislocation mechanisms and 3D twin architectures generate exceptional strength-ductility-toughness combination in CrCoNi medium-entropy alloy

Combinations of high strength and ductility are hard to attain in metals. Exceptions include materials exhibiting twinning-induced plasticity. To understand how the strength-ductility trade-off can be defeated, we apply in situ, and aberration-corrected scanning, transmission electron microscopy to examine deformation mechanisms in the medium-entropy alloy CrCoNi that exhibits one of the highest combinations of strength, ductility and toughness on record. Ab initio modelling suggests that it has negative stacking-fault energy at 0K and high propensity for twinning. With deformation we find that a three-dimensional (3D) hierarchical twin network forms from the activation of three twinning systems. This serves a…

• UD
  U.S. Department of Energy

  Awards: -AC02-05CH11231, 05CH11231, AC02-05CH11231, DE-AC02, DE-AC02-05CH11231, DE-AC02-
• OO
  Office of Science

  Awards: AC02-05CH11231, -AC02-05CH11231, DE-AC02
• BE
  Basic Energy Sciences

  Awards: DE-AC02, AC02-05CH11231, DE-AC02-05CH11231, -AC02-05CH11231
• OR
  Oak Ridge National Laboratory

  Award: DE-AC02-05CH11231
• LB
  Lawrence Berkeley National Laboratory

  Awards: DE-AC02-05CH11231, 05CH11231, AC02-05CH11231