Microstructural Evolution During Friction Stir Welding of Mild Steel and Ni-Based Alloy 625
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Microstructure evolution during friction stir welding (FSW) of mild steel and Ni-based alloy 625 was studied. Regarding the Ni-based alloy, the welding process led to grain refinement caused by discontinuous and continuous dynamic recrystallization, where bulging of the pre-existing grains and subgrain rotation were the primary mechanisms of recrystallization. In the steel, discontinuous dynamic recrystallization was identified as the recovery process experienced by the austenite. Simple shear textures were observed in the regions affected by the deformation of both materials. Although the allotropic transformation obscured the deformation history, the thermo-mechanically affected zone was identified in the steel by simple shear texture components. A new methodology for the study of texture evolution based on rotations of the slip systems using pole figures is presented as an approximation to describe the texture evolution in FSW.
KeywordsSlip System Friction Stir Welding Simple Shear Friction Stir Welding Texture Component
The authors gratefully acknowledge Petrobras (Contract Number 0050.0050438.09.9) for financial support along with the Brazilian Nanotechnology National Laboratory (LNNano-CNPEM), Richard W. Fonda from the Naval Research Laboratory and Hamilton FG Abreu from the Federal University of Ceará for the helpful research discussions.
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