Tailoring the Young's modulus of Ti-Mo-Zr alloys via α"/β phase regulation: Design strategies and mechanisms

A novel low Young’s modulus Ti–Mo–Zr alloy was designed by first-principles calculation and high-throughput additive manufacturing (AM). Unlike the traditional approach of controlling β-phase stability in titanium alloy development, the designed Ti–16Mo–6Zr alloy, consisting of α′′ and β phases, exhibits a low Young's modulus (57.1 ± 3.4 GPa) and a high fracture strain (22.1 % ± 1.8 %). Serial samples with various compositions show that Young’s modulus can be reduced without loss of strength by adjusting the ratio of α′′/β phases reasonably. The mechanism by which the combination of metastable phases influences Young's modulus was elucidated through first-principles calculations of the Crystal Orbital Hamilton Population (COHP) and relevant integrated values. By controlling the amount of Mo atoms, a balance is achieved between Ti–Mo and Ti–Ti bonds withinα′′/β phases. The presence of Ti–Mo bonds induces localized lattice distortions, weakening the Ti–Ti bonds and reducing Young’s modulus. Meanwhile, Ti–Mo bonds are carefully regulated to avoid excessive rigidity in the material. This study has the potential to accelerate the development of Ti–Mo-based alloys, providing novel insights into controlling Young’s modulus by simultaneously regulating multiple metastable phases.

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