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

An analysis of the shape strains produced by the martensitic ??? 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 ? 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 ] / 60o -type, and in the other kind they would all be [ 10 5 5 3 ] / 63.3o. -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.