Temperature distribution and material flow behaviours during refill friction stir spot welding (RFSSW) of AZ91D magnesium alloy were studied by a combination of numerical modelling and experimentation. The coupled Eulerian–Lagrangian (CEL) formulation was adopted to analyse processing thermal history and plastic deformation mechanisms of the RFSSW joint more accurately. Welding thermal cycles of varying positions in joint were measured by thermocouples so as to validate accuracy of this simulation process. The FEA (Finite Element Analysis) simulation to cover mechanical results was found to be consistent with the experimental values. Moreover, simulation analysis presented that material flow caused the clear hook defects and bonding ligament, and such material flow behaviours were experimentally verified via the macrostructure and microstructure of the RFSSW joint.

中文翻译：

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AZ91D镁合金再填充搅拌摩擦点焊过程中温度分布和材料流动的预测与验证

通过数值模拟和实验相结合，研究了 AZ91D 镁合金再填充搅拌摩擦点焊 (RFSSW) 过程中的温度分布和材料流动行为。采用耦合欧拉-拉格朗日 (CEL) 公式来更准确地分析 RFSSW 接头的加工热历史和塑性变形机制。通过热电偶测量接头不同位置的焊接热循环，以验证该模拟过程的准确性。发现涵盖机械结果的 FEA（有限元分析）模拟与实验值一致。此外，模拟分析表明，材料流动导致了明显的钩状缺陷和粘合韧带，