Four tools with different pin centerline deviations were fabricated to friction stir weld (FSW) thick plates of Al–Mg–Zn–Cu alloys. The results show that, compared with the pin without pin centerline deviation, the applying of pin centerline deviation is favorable to improve the flowability of plastic material, enlarging the size of nugget zone, refining the grains and reprecipitated phase particles, enhancing the degrees of dynamic recrystallization and quantity of high angle grain boundaries owing to higher temperature and bigger eccentric force, resulting in the increase of strain hardening. Especially for the used pin with a centerline deviation of 0.2 mm, the highest average hardness and best metallurgical properties of thick FSW joints are produced, and which are consistent with the microstructure evolution and recrystallization behavior. Moreover, the fracture mode of the joints produced by the pins with centerline deviation from 0 mm to 0.3 mm changes gradually from a brittle fracture in the nugget zone (NZ) to a ductile failure in the HAZ.

四种具有不同销中心线偏差的工具被制造到 Al-Mg-Zn-Cu 合金的搅拌摩擦焊 (FSW) 厚板上。结果表明，与无销中心线偏差的销相比，应用销中心线有利于提高塑性材料的流动性，扩大熔核区尺寸，细化晶粒和再沉淀相颗粒，提高塑性材料的动态程度。高温和较大的偏心力导致再结晶和大角度晶界的数量增加，导致应变硬化增加。特别是对于中心线偏差为0.2 mm的旧销，产生了最高的平均硬度和最好的厚FSW接头的冶金性能，并且与组织演变和再结晶行为一致。