Amorphization-templated nanocrystallization endows TiNi alloys with ultrahigh strength and programmable...

The concurrent achievement of high strength, ductility, and superelasticity in metals remains a grand challenge. Conventional TiNi alloys, although superelastic, suffer from low strength and modest superelasticity. Here, we report a bulk nanostructuring strategy that not only overcomes these limitations but also enables programmable mechanical response. By combining moderate cryogenic deformation to create a bulk amorphous precursor with pulsed electric current-driven nanocrystallization, we produce a Ti₄₉Ni₅₁ alloy that exhibits an exceptional combination of properties: a tensile strength over 2 gigapascals (GPa), ductility up to 12%, and a giant recoverable strain of 9%. The enhanced functionality stems from a nanoscale martensitic transformation that proceeds sequentially across nanograins of varying sizes, rather than simultaneously as in coarse-grained materials. This mechanism allows the superelastic response to be tunable, offering tailored stress-strain curves with adjustable transformation stresses and shapes ranging from plateau-like to linear. Our amorphization-templated nanocrystallization method is potentially scalable and bridges the gap between ultrastrong structural materials and advanced functional applications.