Enhance cryogenic ductility and strength of body-centered tetragonal Sn by pre-twinning and recrystallization

Previous researches on high-symmetric metallic materials demonstrate that the introduction of twins can overcome the strength-ductility trade-off. However, it is uncertain if such a pathway is valid for metals with a low-symmetry crystal structure. Here, the low-symmetry body-centered tetragonal Sn achieved a simultaneous enhancement in tensile ductility from 6 % to 14 % elongation and strength from 36 MPa to 60 MPa at 77 K through pre-twinning combined with room-temperature self-recrystallization. The in-situ tensile experiments reveal that the pre-existing and new deformation twins, as well as dynamic recrystallization and multiple dislocation planar slip contribute to the enhancement of cryogenic mechanical properties.