BCC Structural Stability and Deformation Behavior of Ti-Mo Alloys: A Cluster-Model-Embedded First-Principles Study

To elucidate the intrinsic link between the body-centered cubic (BCC) structural stability and the deformation mechanisms of Ti-Mo alloys, first-principles (FP) calculations based on a cluster model are performed for Ti-xMo (x = 2.3, 4.7, 7.8, and 12.5 at. %) binary alloys. Structural models are constructed by embedding a cluster unit within a 4 × 4 × 4 BCC supercell. The formation energies (E_f) and binding energies (E_b) of the α and β phases indicate that BCC structural stability increases with higher Mo content, and that the Ti-12.5Mo alloy is energetically favored to form a single β phase. For the metastable Ti-4.7Mo alloy, the negative value of G(101)[101¯] indicates lattice softening, while the value of G_(101)[010] = 3.9 GPa is lower than those of G(323)[13¯1] and G(110)[11¯1]. Both features facilitate the stress-induced α″ transformation. Conversely, in the stable Ti-12.5Mo alloy, G_(011)[100] reaches 36 GPa, substantially exceeding G(123)[111¯], thereby suppressing α″-phase transformation and promoting dislocation slip. The present cluster model-embedded first-principles calculations demonstrate that the shear modulus serves as a valid descriptor linking BCC structural stability to deformation behavior in Ti-Mo alloys.