Texture Evolution within the Thermomechanically Affected Zone of an Al-Li Alloy 2195 Friction Stir Weld

Friction stir welding (FSW) of Al-Li alloy 2195 plate produces strong texture gradients. The microstructural characteristics evolve from the base plate, through the thermomechanically affected zone (TMAZ), to the weld nugget interface. In the current study, electron backscattered diffraction (EBSD) analyses were employed to quantify the spatial distribution of texture gradients associated with the evolution of texture within the TMAZ. The strong texture of the base plate enabled the texture evolution to be characterized as a function of location. Systematic partitioning of EBSD data relative to the degree of lattice rotation at each point accurately captured the crystallographic transitions across the advancing side TMAZ. Over a large section of this region, the texture evolves as a result of continuous rigid body rotations. The rigid body rotations were correlated with the complex material flow patterns commonly associated with the FSW process and prior observations of shear-related textures. Finally, a correlation between texture and fracture in a subscale tensile specimen is observed, where failure occurs within a visible band of low-Taylor factor grains.