Achieving large near-linear elasticity, low modulus, and high strength in a metastable β-Ti alloy by mild cold rolling

Simultaneously achieving high elasticity, low modulus, and high strength in Ti alloy has been a longstanding challenge. In this study, cold rolling was conducted to modulate the martensitic transformation of the Ti-15Nb-5Zr-4Sn-1Fe alloy to address this challenge. The 10% cold rolling process was primarily accommodated by a novel stress-induced sequential β-to-α′′-to-αʹ martensitic transformation accompanied by the disappearance of ω phase, which was sufficient to induce adequate martensite and defects to suppress the initial rapid stress-induced martensitic transformation, without destroying the equiaxed shape of prior β grains. Consequently, the novel sequential phase transformation led to a substantial decrease in Young's modulus by 50.5% while increasing the strength, resulting in an excellent combination of large near-linear elasticity of 2.34%, low modulus of 45 GPa, and high strength of 1093 MPa. The obtained large near-linear elasticity was mainly contributed by the concurrent low modulus and high strength obeying Hooke's law. These findings provide valuable insights into the attainment of concurrent high elasticity and low modulus in Ti alloys by regulating the stress-induced sequential martensitic transformation.