The strengthening mechanisms and incipient plasticity of additively manufactured biomedical refractory high entropy alloys

Owing to the cellular structure that limits dislocation motion upon stress loading, additively manufactured (AM) refractory high-entropy alloys (HEAs) exhibit an excellent strength-plasticity synergy. This work integrates micro/nano-mechanical experiments with statistical physics modeling to examine dislocation nucleation and slip in AM-fabricated TiNbTaZrMo HEA. Computational results indicated that the activation volume for initial dislocation nucleation is about one atomic volume, facilitating dislocation initiation. Nanoindentation and in-situ micro-pillar compression reveal no significant pop-in events, indicating that the cellular structure impedes dislocation slip and thus prevents plasticity reduction from dislocation slipping near grain boundaries. This work provides a thorough investigation into the interplay between incipient plasticity, dislocations, and cellular structure in AM-produced TiNbTaZrMo, offering new insights into the design and advancement of AM-fabricated refractory HEAs.