Revealing the local lattice strains and strengthening mechanisms of Ti alloys

Abstract In this work, effects of solute atoms (X) on lattice parameters, bulk modulus, enthalpy of formation, lattice distortion energy, electron work function (EWF) and bonding morphology/strength of HCP Ti 95 X are comprehensively studied by first-principles calculations. Here, X includes the α-stabilizer Al, and the β-stabilizer Cr, Mo, V and Nb, which are commonly combined in the high-strength Ti7333 and Ti5553 alloys. Attributing to various atomic size and number of valence electrons of these solute atoms, the mechanical (lattice distortion) and the chemical (solute atom) contributions to the local lattice strains are clearly distinguished in terms of lattice distortion energy and bonding charge density. It is found that the equilibrium volume of Ti 95 X decreases linearly with the increased HCP volume of each solute atom. The less change of volume yields minimum lattice distortion energy. Moreover, a higher value of Δρ caused by the electron redistributions of solute atoms than the matrix indicates an improved bonding strength via the coupling effects of lattice distortion and valence electrons. The bonding strength of Ti 95 X increases in the order of Ti-Al