The effect of stacking fault energy (SFE) on the grain structure evolution of face-centered cubic metals during friction stir welding was investigated by using pure aluminum, pure copper and Cu–30Zn alloy as experiment materials. Tool “stop action” and rapid cooling were employed to “freeze” the microstructure of the flowing materials around the tool. Marker materials were used to show the streamline of the material flow. The microstructures of the three materials at different welding stages were contrastively studied by the electron backscatter diffraction technique. The results show that at the material flow stage, as the SFE decreases, the grain structure evolution changes from the continuous dynamic recrystallization to discontinuous dynamic recrystallization, and further to the dynamic equilibrium between the annealing twinning due to thermally activated grain boundary migration and the twin destruction during the plastic deformation. Owing to different grain structure evolution mechanisms, the grain structure at the end of the material flow is greatly different. Especially in copper, a lot of dislocations remain, which gives rise to the static recrystallization occurring during the subsequent cooling stage.

中文翻译：

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搅拌搅拌过程中堆垛层错能量对FCC金属晶粒组织演变的影响

以纯铝，纯铜和Cu-30Zn合金为实验材料，研究了堆垛层错能（SFE）对摩擦搅拌焊过程中面心立方金属晶粒结构演变的影响。使用工具“停止动作”和快速冷却来“冻结”工具周围流动材料的微观结构。标记材料用于显示物料流的流线。通过电子背散射衍射技术对比研究了三种材料在不同焊接阶段的显微组织。结果表明，在材料流动阶段，随着SFE的降低，晶粒结构的演变从连续动态再结晶转变为不连续动态再结晶，以及由于热活化晶界迁移引起的退火孪晶与塑性变形过程中的孪晶破坏之间的动态平衡。由于不同的晶粒结构演化机制，物料流结束时的晶粒结构有很大不同。特别是在铜中，会保留许多位错，这会导致在随后的冷却阶段中发生静态的重结晶。