Structural distortion-induced acoustic velocities and elasticity softening in compressed (TiZrNbTaW)C high-entropy carbide

Unraveling pressure-induced elastic weakening mechanisms is crucial for understanding and exploring the structure–property–pressure relationships of high-entropy carbides (HECs). Using in situ synchrotron x-ray diffraction and ultrasonic interferometry, we investigate the microstress-promoted structural evolution, sound velocities, and elastic properties of (TiZrNbTaW)C at high pressure. Interestingly, an anomalous softening behavior in both sound velocities and elastic moduli of (TiZrNbTaW)C is observed upon nonhydrostatic compression, which is an unexpected phenomenon that is absent after annealing of the cold-compressed specimen at a high temperature of ∼1300 K. The underlying mechanism is attributed to microstress-enhanced lattice distortion at high pressure, which drives the elastic softening. These findings provide a mechanistic framework for the lattice distortion–elasticity interaction in HECs at high pressure, and offer actionable guidance for their applications at extreme environments.