Brittleness

Nanotechnology

Nanoscopic scale

Crystal twinning

Crystallography

Ultimate tensile strength

Creep

Strain hardening exponent

Hexagonal crystal system

Composite material

Chemistry

Metallurgy

Materials science

Ductility (Earth science)

Work hardening

Alloy

Titanium

Microstructure

Titanium alloy

Science

Nanostructured metals are usually strong because the ultrahigh density of internal boundaries restricts the mean free path of dislocations. Usually, they are also more brittle because of their diminished work-hardening ability. Nanotwinned materials, with coherent interfaces of mirror symmetry, can overcome this inherent trade-off. We show a bulk nanostructuring method that produces a multiscale, hierarchical twin architecture in a hexagonal closed-packed, solute-free, and coarse-grained titanium (Ti), with a substantial enhancement of tensile strength and ductility. Pure Ti achieved an ultimate tensile strength of almost 2 gigapascals and a true failure strain close to 100% at 77 kelvin. The multiscale twin structures are thermally stable up to 873 kelvin, which is above the critical temperature for many applications in extreme environments. Our results demonstrate a practical route to achieve attractive mechanical properties in Ti without involving exotic and often expensive alloying elements.

Cryoforged nanotwinned titanium with ultrahigh strength and ductility