TEXTURE EVOLUTION DURING FRICTION STIR WELDING OF STAINLESS STEEL

摘要

Texture evolution during friction stir welding (FSW) of stainless steel was investigated using both experimental measurements and model predictions based on a polycrystal plasticity. Material undergoes heating and deformation sufficient to alter its microstructural state during FSW. Texture evolution is quite complex in FSW, owing in particular to its dynamics under the induced stirring motion. Modeling approaches help to better understand how the stirring can both strengthen and weaken textures, which is an essential element in a complete description of texturing during FSW. In a two-dimensional way, texture stability is addressed from the computed velocity gradients along streamlines of the flow field. The texture is assumed to be uniform initially and shows monoclinic sample symmetry after deformation. Upstream and downstream of the tool, the deformation is nearly monotonic, causing little change of the texture. Around the tool pin, the texture strengthens, weakens, and restrengthens. The mixture of pure and simple shear textures was found. The effects of frictional conditions with the tool pin and shoulder on the complicated flow and texture evolution in the through thickness were examined with a three-dimensional approach. Trends in regard to strengthening and weakening of the texture were discussed in terms of the relative magnitudes of the deformation rate and spin. The computed textures were compared to EBSD measurements and were discussed with respect to distributions along orientation fibers and the dominant texture component along the fibers.