Strengthening Near‐ α Titanium Alloys via Phase‐Transformation‐Induced High‐Density Nanotwins

To address the challenge of inducing high‐density twin substructures via phase transformation in near‐ α titanium alloys, which is restricted by the high stacking fault energy of the hexagonal close‐packed structure, this study aims to achieve the controllable formation of high‐density nanotwins by exploiting the structural transformation characteristics of the martensitic transformation. The results indicate that as the solution temperature increases, the microstructure evolves from a basket‐weave α + β dual‐phase structure to fine acicular α ′ martensite. Notably, high‐density nanotwins were induced within the α ′ laths after water quenching from 1090°C. This microstructural evolution is attributed to the severe lattice shear and high strain‐energy accumulation during the martensitic transformation, where the substantial transformation strain energy is accommodated by a self‐coordinating shear mechanism through the formation of twins. Mechanical testing reveals that the tensile strength initially increases and then decreases with solution temperature. The 1090°C‐treated alloy exhibits a peak room‐temperature ultimate tensile strength (UTS) of 1425.9 MPa with an elongation of 6.6%, while retaining a high UTS of 1005.2 MPa and an elongation of 8.8% at 600°C. The high‐density nanotwin boundaries constitute a dense network of barriers to dislocation motion, providing a significant contribution in static strengthening at both room and elevated temperatures.