Abstract: Heterogeneous laminated composites present a promising approach to overcome the strength-ductility trade-off in structural materials. However, their deformation mechanisms under cryogenic conditions are not yet fully understood, which hinders their application in low-temperature environments. Here, we design Ti/Ti6Al4V laminated composites with tailored layer thicknesses and report an unusual strain-hardening behavior at 77 K, mediated by interfacial-constraint-induced {10-12} twins. Through in situ cryogenic electron backscatter diffraction, we for the first time correlate the twin dynamics at cryogenic temperatures with the layer thickness (serving as the key structural parameter for laminated composites) and the width of the interface-affected zone (serving as the key physical parameter for interfacial mechanics). This correlation leads to the key finding that a strong interfacial constraint is generated when the softer titanium layer is fully covered by two neighboring interface-affected zones, potentially triggering unique behaviors such as the unusual strain hardening observed in this study. Thus, our work provides a generalizable strategy for designing high-performance cryogenic laminates and advances the potential applications in aerospace and energy systems operating in extreme environments.

Key words: Cryogenic deformation, Hexagonal metal, Mechanical property, Electron backscatter diffraction