Effect of self-accommodation on α/ α boundary populations in pure titanium

Abstract

An analysis of the shape strains produced by the martensitic β→ α transformation in pure titanium indicates that there are three likely slip systems which could operate to give the complementary shear. The greatest degree of self-accommodation of the shape strains was given by clusters of three variants of α grains and two kinds of clusters were identified. In one kind of cluster, the high-angle grain boundaries (HAGBs) formed between adjacent laths of different variants would all be 1 1 2 ̄ 0 60 ∘ -type, and in the other kind they would all be 1 0 5 5 3 63.3 ∘ -type. Analysis of the frequency distributions for misorientation angles in pure Ti using electron backscattered diffraction confirms a strong preference for the formation of these two types of HAGBs, with 78% of the HAGBs being classed as such, as compared to 36% which one would expect for a random distribution of variants. A statistical analysis of nucleation, which accounts for the observed frequencies of the different types of HAGBs, is proposed.