Abstract The bobbin tool friction stir welding (BTFSW) technique was applied to a Mg-Zn-Zr alloy, ZK60-T5. The effects of shoulder diameter and stir pin geometry on the macrostructure, microstructure and mechanical properties of the BTFSW joints were studied. Weld quality was sensitive to the interaction of bobbin tool geometries and processing parameters. The reduction in the shoulder diameter led to less frictional contact and resistance and hence lowered the mechanical load imposed on the tool. The employment of the tapered stir pin reduced the traversing force, which displaced substantially less plasticized metal during the BTFSW than the cylindrical stir pin. The welding speed for the BTFSW was increased benefiting from these mechanical load alleviations. The visual aspects of the BTFSW joints, characterized by limited tunneling and voiding phenomena occurring were improved with the increase in welding speed. The BTFSW resulted in extensive softening in the stir zones of the joints due to dissolution of the β2´precipitates. The tensile properties of the joints were inferior to those of the base metal due to the crystallographic isotropy in the stir zone. The improvements in tensile properties of the BTFSW joint were achieved through texture tailoring by adding threads on the stir pin. The complicated plasticized metal flow introduced by the threaded stir pin provided a randomized crystallographic texture in the stir zone which contributed to the preferable tensile properties.

中文翻译：

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调整刀具几何形状提高 Mg-Zn-Zr 合金线轴刀具搅拌摩擦焊质量

摘要 线轴工具搅拌摩擦焊（BTFSW）技术应用于Mg-Zn-Zr合金ZK60-T5。研究了肩部直径和搅拌销几何形状对 BTFSW 接头的宏观结构、微观结构和力学性能的影响。焊接质量对线轴工具几何形状和加工参数的相互作用很敏感。肩部直径的减小减少了摩擦接触和阻力，从而降低了施加在工具上的机械载荷。锥形搅拌销的使用降低了横向力，在 BTFSW 期间，与圆柱形搅拌销相比，其移动的塑化金属显着减少。得益于这些机械负载的减轻，BTFSW 的焊接速度得到了提高。BTFSW 关节的视觉方面，随着焊接速度的增加，出现的隧道和空洞现象有限的特点得到了改善。由于 β2' 沉淀物的溶解，BTFSW 导致接头搅拌区的大量软化。由于搅拌区的结晶各向同性，接头的拉伸性能不如母材的拉伸性能。BTFSW 接头拉伸性能的改进是通过在搅拌销上添加螺纹进行纹理剪裁来实现的。螺纹搅拌针引入的复杂塑化金属流在搅拌区提供了随机的晶体结构，这有助于获得更好的拉伸性能。由于 β2' 沉淀物的溶解，BTFSW 导致接头搅拌区的大量软化。由于搅拌区的结晶各向同性，接头的拉伸性能不如母材的拉伸性能。BTFSW 接头拉伸性能的改进是通过在搅拌销上添加螺纹进行纹理剪裁来实现的。螺纹搅拌针引入的复杂塑化金属流在搅拌区提供了随机的晶体结构，这有助于获得更好的拉伸性能。由于 β2' 沉淀物的溶解，BTFSW 导致接头搅拌区的大量软化。由于搅拌区的结晶各向同性，接头的拉伸性能不如母材的拉伸性能。BTFSW 接头拉伸性能的改进是通过在搅拌销上添加螺纹进行纹理剪裁来实现的。螺纹搅拌针引入的复杂塑化金属流在搅拌区提供了随机的晶体结构，这有助于获得更好的拉伸性能。BTFSW 接头拉伸性能的改进是通过在搅拌销上添加螺纹进行纹理剪裁来实现的。螺纹搅拌针引入的复杂塑化金属流在搅拌区提供了随机的晶体结构，这有助于获得更好的拉伸性能。BTFSW 接头拉伸性能的改进是通过在搅拌销上添加螺纹进行纹理剪裁来实现的。螺纹搅拌针引入的复杂塑化金属流在搅拌区提供了随机的晶体结构，这有助于获得更好的拉伸性能。