Abstract: Twin boundary (TB) is a special and fundamental internal interface that plays a key role in altering the mechanical and physical properties of materials. However, the atomistic deformation mechanism of TB re-mains under debate, of which the most concerned aspect is how TB would affect the mechanical strength and plasticity of a material. Herein, we introduce our new discovery that the pseudoelastic strain of a TB can recover with decomposition and escape of pile-up dislocations, demonstrated by imposing a sponta-neous pseudoelastic deformation with recoverable plastic bending strain up to 5.1% on a TB. We found that the steps on the curved TB gradually annihilated during the migration of the TB, which was in-duced by the slip of decomposition dislocations on the TB. The TB not only provides local strain harden-ing through interaction with dislocations during the loading stage but also acts as a channel for the fast movement of decomposition dislocations during the recovery stage. Beside, the TB can maintain excellent pseudoelasticity under a multicycle bending test, which may play an important role in improving the fa-tigue resistance of materials. These findings could open up a new avenue for optimizing the mechanical properties of materials by manipulating their twin boundaries at the nanoscale.

Key words: Twin boundary, Pseudoelasticity, Migration, Dislocation-twin boundary interaction