Unveiling the mechanisms of solid-solution strengthening in Ti alloys with dual-phase structures: an in-depth first-principles investigation

Titanium alloys have been widely used in the aerospace industry attributing to their superior mechanical properties. Conducted from a microscopic perspective, this work unveils the objective laws and intrinsic mechanisms of solid-solution strengthening in dual-phase Ti alloys. This study delves into β-Ti₉₅X and α-Ti₉₅X alloys, where X represents Al, Cr, Mo, Nb, and V. The basic physical properties including lattice constants, equilibrium volume, bulk modulus (B₀), enthalpy of formation (ΔH), lattice distortion energy (ΔE_LD), electron work function (EWF), and bonding characteristics are analyzed. The results indicate that the α phase exhibits greater stability compared to the β phase due to differences in crystal structure. However, solid solution strengthening is more pronounced in the β phase, where larger solute atoms induce greater lattice distortion, significantly influencing the mechanical properties of Ti alloys. Further insights are gained by analyzing the bonding charge density and electronic density of states, providing a deeper understanding of the interactions between solute atoms and Ti atoms. Moreover, a power-law model is established between Young’s modulus (E) and EWF, providing essential theoretical and data support for the development of new high-performance Ti alloys.