Unprecedented mechanical properties of the novel TWIP/TRIP titanium alloys are controlled by {332}113 twinning and stress-induced martensitic transformation

which can operate separately

simultaneously or even in synergy

following a still unclear atomic-scale mechanism. Using

ab initio

calculations and experimental observations

we show that {332}113 twinning can be described as a polymorphic solid-state transformation able to produce either twinned or martensitic structures with a unified transformation path. The required lattice strains and atomic shuffles are provided by the shear-shuffle mechanism of twin operation

of which trajectory

due to accompanied atomic relaxation

is not linear and strongly influenced by

β

phase stability.