In situ EBSD study of deformation behavior of primary α phase in a bimodal Ti-6Al-4V alloy during uniaxial tensile tests

Uniaxial tension experiments and electron backscatter diffraction were performed on a bimodal Ti-6Al-4V alloy to study in situ the deformation behavior of primary hcp-Ti (α_p). It was found that the strain could be accommodated by the activation of slip systems and by grain rotations. The prismatic slip was the primary slip mode of the α_p. From the analysis of kernel average misorientation and geometrically necessary dislocation, it was shown that the dislocations mainly distributed in the vicinity of grain and sub-grain boundaries, and part of the dislocations distributed around slip lines. It was the dislocation activities that led to the formation of the low angle grain boundary and its transformation to the high angle grain boundary. It's important that tracking of deformation heterogeneities with significance to performance. By analyzing the rotation angle, average rotation rate, and rotation path of grains, it was shown that grain rotation heterogeneity occurred during the deformation. From the observation of the loading direction, grain rotation paths kept with the texture evolution direction of all α_p. The grains activated in the basal slip gradually rotated to the ⟨101¯1⟩ pole and enhanced the intensity of the ⟨101¯1⟩ texture. Meanwhile, the grains activated in prismatic or 1st-order pyramidal slip rotated to the ⟨101¯0⟩ pole and enhanced the intensity of the ⟨101¯0⟩ texture. Grain rotation and texture evolution are related to mechanical properties.