In situ EBSD investigation of microtexture evolution and slip activation of α macrozones during tensile deformation in Ti-6Al-4V alloy

Abstract

The macrozone with sharp local texture is known as a potential cause of the reduced fatigue resistance and lifetime of titanium alloys. In this work, the microtexture evolution and slip activation of α macrozones during tensile deformation in Ti-6Al-4V alloy were analyzed by in situ EBSD. The results indicate that the α macrozones rotate with the orientation change under tensile deformation. The destruction of macrozones occurs when the c axis of the macrozone nearly overlaps with the stress direction. In such a case, the activation of the basal slip system is insufficient, which leads to severe stress concentration and local dislocation accumulation. Consequently, the α laths within the macrozone partially rotates to other directions for pyramidal <c+a> slip system activation. The large macrozone is thus segmented by the rotated α phase. In addition, a small rotation of the macrozone occurs when the angle between the tensile direction and the c-axis (θ) increases. In such a case, both basal and pyramidal <c+a> slip systems activate and contribute to the c-axis deformation. Thus, the deformation is homogeneous and the dislocation density is low within the macrozone. If only the pyramidal <c+a> slip system is activated, the macrozone nearly remains unchanged during deformation over a wide range of θ values. This work provides an available route to control macrozones in titanium alloys by pre-deformation.