Some aspects of the variation of the strain anisotropy in titanium

Strain anisotropy in commercial purity titanium was studied between 77° and 973°K using the technique of Rittenhouse and Picklesimer. Both longitudinal and transverse tensile specimens were used that were machined from a plate with a strong alignment of the basal planes of the grains parallel to the rolling plane. The contractile strain along the transverse plate direction was always larger than that parallel to the rolling plane normal. The strain anisotropy was greatest at the highest temperature. With decreasing temperature it became smaller at an ever increasing rate. At 973°K the strain anisotropy was strain independent. At lower temperatures it decreased with increasing strain. It is believed that deformation twinning can account for most of the temperature and strain dependence of the strain anisotropy. Quantitative microstructure studies show good correspondence between changes in the volume fraction of twins and changes in the strain anisotropy. Transverse specimens exhibited a greater degree of strain anisotropy, and this is consistent with the original texture of the titanium plate used in this investigation.