The Effect of Aluminium on Deformation and Twinning in Alpha Titanium: The ND Case

Abstract

The deformation behavior of binary Ti-Al model alloys (0 to 13at.%) has been observed during compression normal to the rolling direction with respect to the activity of {1 1 2 2} compression twins but also the more common {1 1 2 0} tension twin as well as the rarely seen {1 1 2 1} tension twins. In-situ neutron diffraction loading experiments and EBSD microstructure analysis were used to qualify the impact of Al on twinning. The results show that for the given loading direction and starting texture,{1 1 2 2} and {1 1 2 0} twinning are similarly common in commercially pure Ti, while only small additions of Al result in a dramatic decrease in {1 1 2 2} compression twinning. In contrast, dramatic reductions of {1 1 2 0} twin fractions are only observed above 10at.% Al and with an ageing treatment to promote Ti 3 Al formation. Al addition until 10at.% makes {1 1 2 1} twinning more likely, but Ti 3 Al formation seems to deactivate this twin system. The role of slip on twinning is discussed.