The shear textures that develop in friction stir welds are reviewed and discussed. In all the materials examined, including face centred cubic (fcc), body centred cubic (bcc) and hexagonal close-packed (hcp) materials, friction stir welding produces a predominant shear texture with the close-packed directions aligned with the shear direction (SD) and the close-packed plane normal perpendicular to both the SD and the shear plane normal. This orientation corresponds to the B/ B B ideal shear texture in fcc materials, the D 1 ideal shear texture in bcc materials, and the P 1 ideal shear texture in hcp titanium alloys. Titanium friction stir welds fabricated above the b transus temperature can contain evidence of ideal shear texture components from both the bcc D 1 (after transformation to the hcp phase according to the Burgers orientation relationship) and the hcp P 1 shear textures. Thus, similar shear textures develop in friction stir welds of fcc, bcc and hcp materials.

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Generation of realistic artificial 3D grain structures for use in modeling has gained increasing attention during the last two decades due to significant enhancements in the capabilities of large-scale 3D computer simulations. One commonly chosen model is the Laguerre tessellation (also known as weighted Voronoi tessellations or power diagrams). [1] As in the case of the classical Voronoi tessellation, Laguerre tessellations also partition space into convex polyhedra with planar faces. The advantage of the Laguerre tessellations, compared to the classical Voronoi tessellation, is that it allows for a wider range of grain structures by means of weighting factors.

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The microstructure across a friction stir weld in aluminum alloy 2195 was analyzed to reveal the precipitation processes, grain evolution mechanisms, and crystallographic texture within that weld. The complex microhardness variations across the weld are explained by the observed precipitation sequence, in which the original precipitates coarsen and dissolve during welding, and are then replaced by different precipitates, which form during cooling. The grain development from the thermomechanically affected zone (TMAZ) into the weld nugget reveals that subgrains form within the TMAZ grains and develop increasing boundary misorientations through continuous dynamic recrystallization by subgrain rotation to eventually form the refined grains observed within the weld nugget. Within the weld nugget, a {112},110. texture is observed, corresponding to a high strain/high temperature shear strain component.