Origin of dramatic oxygen solute strengthening effect in titanium

Screw dislocations: A hard case to crack The motion of dislocations or defects in a metal influences its strength and toughness. If these defects can be “pinned” by adding alloying elements, it should be possible to create a stronger alloy. It was thought that there shouldn't be much of an interaction between screw dislocations and any alloying elements. However, Yu et al. show that for α-Ti, the profound hardening effect of oxygen is due to the strong interactions with the core of the dislocations. First-principles calculations reveal that distortion of the interstitial sites at the dislocation core creates a very strong but short-range repulsion for oxygen atoms. Science , this issue p. 635