AbstractThe effect of grain size on the mechanical properties of metastable Ti–15V–3Cr–3Sn–3Alβtitanium alloy has been investigated. In the solution annealed condition the small grain sized specimens are of strength higher than the large grain sized specimens. However, when the alloy is aged the large grain sized specimens become the stronger. The aged, large grain sized specimens have also improved fracture toughness. This unexpected behaviour is explained by means of models which incorporate the contributions of the grain boundaries and the grain interior to the strength and fracture toughness.MST/1365