EFFECT OF YTTRIUM AND ERBIUM DISPERSOIDS ON THE DEFORMATION-BEHAVIOR OF TITANIUM

The deformation characteristics at 295 K and 575 K of polycrystalline Ti-Y and Ti-Er alloys containing 20 to 90 nm diameter dispersions were investigated by stress-strain measurements and by transmission electron microscopic observations of deformation substructures. The presence of the dispersoids increases the yield stress at both 295 K and 575 K, with the dispersion strengthening being more pronounced for the larger grain size and at the higher temperature. In dispersoid-free titanium the yield stress varies with grain size at both 295 K and 575 K in accordance with the Hall-Petch relation, but the yield stress of the Ti-Er alloys does not show a well-defined linear dependence on the inverse square root of grain size. The work hardening is less sensitive to grain size in the Ti-Er alloys than in pure titanium. The extent of twinning is significantly higher in the Ti-Er and Ti-Y alloys than in titanium at both temperatures. The influence of the dispersoids on deformation substructure and grain size related deformation behaviour is discussed. © 1979 Chapman and Hall Ltd.