| Abstract Scope |
Despite of their simple face-centered cubic crystal structure, CoNi–based medium-entropy alloys (MEAs), such as equimolar CoNiCr and CoNiV, exhibit exceptional mechanical properties across a wide range of temperatures and loading conditions due to a cascade of deformation modes. This talk explores the mechanical behavior of compositionally tuned CoNi-based MEAs with varied lattice distortion and stacking fault energy (SFE). Increasing the lattice distortion and reducing the SFE of MEAs by controlled additions of Mo promote a combination of deformation mechanisms, including planar dislocation slip, stacking fault, and nano twinning. These cooperative deformation mechanisms sustain a high strain-hardening rate, delaying deformation instability and enabling the strength-ductility synergy. In addition, using nano-indentation, electron back-scattered diffraction, and transmission electron microscopy, we will explore the small-scale and crystal orientation-dependent mechanical behavior in the MEAs. The results demonstrate a pathway to unlocks fault-mediated strengthening for designing ultrastrong yet ductile MEAs. |