TEXTURE EVOLUTION DURING FRICTION STIR WELDING OF STAINLESS STEEL

摘要

Texture evolution during friction stir welding (FSW) of stainless steel was investigated usingboth experimental measurements and model predictions based on a polycrystal plasticity. Materialundergoes heating and deformation sufficient to alter its microstructural state during FSW. Textureevolution is quite complex in FSW, owing in particular to its dynamics under the induced stirringmotion. Modeling approaches help to better understand how the stirring can both strengthen and weakentextures, which is an essential element in a complete description of texturing during FSW. In atwo-dimensional way, texture stability is addressed from the computed velocity gradients alongstreamlines of the flow field. The texture is assumed to be uniform initially and shows monoclinicsample symmetry after deformation. Upstream and downstream of the tool, the deformation is nearlymonotonic, 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 frictionalconditions with the tool pin and shoulder on the complicated flow and texture evolution in the throughthickness were examined with a three-dimensional approach. Trends in regard to strengthening andweakening of the texture were discussed in terms of the relative magnitudes of the deformation rate andspin. The computed textures were compared to EBSD measurements and were discussed with respect todistributions along orientation fibers and the dominant texture component along the fibers.