Improving the mechanical processing of titanium by hydrogen doping: A first-principles study

Abstract Solute H in Ti alloys has an important effect on their deformation and ductility, therefore changing the mechanical properties and improving the mechanical processing. We have performed first-principles calculations to investigate the effects of H on the mechanical properties of the hexagonal close packed α-Ti and the body centered cubic β-Ti, and make an attempt to understand how the solute H improves the mechanical processing. We compute the structural parameters, elastic properties, and the generalized stacking fault energies for α- and β-Ti with and without the H addition. We find H decreases the shear moduli and the unstable stacking fault energies of α-Ti, enhancing the deformation tendency, while these quantities are increased by H in β-Ti. We predict the H effect on the ductility using different criteria, and find H makes α-Ti more ductile, but raises the brittleness of β-Ti. Our results indicate H may have a favorable effect on improving the mechanical processing of Ti alloys.