Composition design of Ti-Mo-based multi-component TWIP titanium alloys based on specific orientation moduli

To precisely control the thermally/stress-induced products in β-type titanium alloys and overcome the limitations of traditional design methods relying on parameters such as d-electron alloy theory and molybdenum equivalent， a design approach based on specific orientation moduli （Young’s modulus E100， tetragonal shear modulus C′， and shear modulus G111） is proposed. Three Ti-Mo-based multi-component alloys with significant twinning-induced plasticity（TWIP） effect， namely Ti-13.5Mo-3.6Nb（mass fraction/%， the same below）， Ti-13Mo-4.5Nb-1.6Zr， and Ti-12.5Mo-6.5Nb-1.5Zr-0.9Al， are successfully designed. By means of optical microscopy（OM）， transmission electron microscopy（TEM）， electron backscatter diffraction （EBSD）， and tensile testing， the cold workability， thermally-induced metastable phases， and stress-induced deformation modes of the designed alloys are systematically analyzed， and the regulation of specific orientation moduli on thermally/stress-induced products is investigated. The results show that all three designed alloys exhibit excellent cold workability with a cold working rate of over 90%， and the solution-treated microstructure consists of a β-phase matrix and trigonal thermally-induced ω-phase. Their yield strength ranges from 370 to 428 MPa， total elongation from 46% to 50%， and the deformation mode is dominated by ｛332｝β〈113〉β twinning. The high Young’s modulus E100（22.9 GPa） of the three alloys completely suppresses the thermally/stress-induced α″-martensitic transformation； the low tetragonal shear modulus C′（7.8 GPa） facilitates ｛332｝β〈113〉β twinning， resulting in a twin area fraction of 28.8%-30.1% at 5% deformation； the high shear modulus G111（10.6-10.7 GPa） inhibits the collapse process of the thermally-induced ω-phase， thereby maintaining the trigonal structure of the thermally-induced ω-phase. The design approach based on specific orientation moduli proposed in this study enables the efficient design of Ti-Mo-based multi-component TWIP titanium alloys， combining innovation and practicality. It provides a new pathway for the research and development of high-performance titanium alloys，and possesses broad engineering application prospects.