A new twinning mechanism induced by solute electronic structures

Twin boundaries are frequently observed in polycrystalline materials, significantly influencing their stability and mechanical properties. In this study, we reveal a previously unidentified growth twinning mechanism induced by solute segregation, wherein changes in local electronic structure dictate twin formation. Aberration-corrected scanning transmission electron microscopy, combined with energy-dispersive spectroscopy, demonstrates that the interfacial segregation of W atoms triggers growth twinning in (V, W)C precipitates. Notably, the formation of twin boundaries is highly sensitive to the local W concentration, with a high segregation level of up to 50 at% promoting twin formation, whereas a lower concentration of 20 at% suppresses it. First-principles calculations further reveal that this twinning mechanism originates from a local coordination shift, transitioning from the octahedral geometry characteristic of VC to the mirror-symmetric trigonal coordination of W2C at elevated W concentrations. These findings provide a deeper understanding of solute-induced twinning and offer a pathway for precise control of twin events in crystalline materials.