Stacking Fault Driven Phase Transformation in CrCoNi Medium Entropy Alloy

Phase transformation is an effective means to increase the ductility of a material. However, even for commonly observed face-centered-cubic hexagonal-close-packed (fcc-to-hcp) phase transformation, underlying mechanisms are far from being settled. In fact, different pathways have been proposed, especially with regard nucleation hcp at nanoscale. CrCoNi, so-called medium-entropy alloy, fcc-to-hcp has long anticipated. Here, we report in situ loading study neutron diffraction, which revealed bulk CrCoNi 15 K under tensile loading. By correlating deformation characteristics fcc development phase, it shown that was triggered by intrinsic stacking faults. The confirmation adds myriads available together underpin unusually large low temperatures.