Theory of strengthening of alpha titanium by interstitial solutes

It is assumed that the core structure of screw dislocations in the h.c.p. lattice of α-Ti can be described by a sessile splitting on the prism plane and on the first order pyramidal plane simultaneously and that slip can proceed after its transformation into a glissile configuration on the prism plane. The strengthening by interstitial solutes O, N, C is explained by their impeding role in these sessile-glissile transformations. A good agreement between the theoretical temperature dependences of the effective stress for different interstitial content and the experimental values can be reached if the effect of impurities on the stacking fault energies is also taken into account. The similarity between the role of screw dislocations in the low temperature deformation of h.c.p. metals with more slip systems operating and of b.c.c. metals is stressed.