Influence of transformation temperature on microtexture formation associated with alpha precipitation at beta grain boundaries in a beta metastable titanium alloy

Overview & Synopsis

The influence of transformation temperature on microtexture development associated with α precipitation at β/β grain boundaries (GB) in the near-β Ti17 alloy was studied using electron backscatter diffraction and considering isothermal treatments. For the alloy studied and the temperature range considered, decreasing the transformation temperature decreased the local microtexture strength within each prior β grain because of a larger number of αWGB colonies (standing for α Widmanstätten GB) formed per β grain, each colony increasing by one the number of α orientations inside each prior β grain. This larger number of αWGB colonies was a consequence of faster formation along β/β GB of their precursors, the allotriomorphic αGB grains (standing for α-GB) at lower transformation temperatures, as evidenced by detailed examination of the first stages of αGB formation. αGB crystallographic orientations frequently followed a variant selection (VS) criterion based on the alignment of (0 1 1)β//(0 0 0 1)αGB//(0 1 1)β. From a statistically relevant number of observations, VS was found to be more frequent at a lower transformation duration and a lower temperature, but the effect was not significant enough to influence the final α microtexture, considered at the scale of one prior β grain. αGB grains that followed the VS criterion emitted two αWGB colonies on either side of the β/β GB more frequently than those with no particular orientation.