摘要双轴肩搅拌摩擦焊接技术是传统搅拌摩擦焊接技术的提升和改进，具有绿色环保无烟尘，不需要填充材料，焊接效率较高，操作方便简单等特点。本文针对7。8mm厚6061铝合金进行BTFSW焊接试验，对焊接过程中的特征参数进行检测与焊接组织分析，对焊接质量进行了金相组织分析与硬度分析，研究底部散热前提下焊接工艺对接头各区域组织与力学性能的影响规律。

在焊接过程中对底部进行散热，依据金相组织发现了其焊接接头的各部分区域即焊核区、热机影响区、热影响区的组织均发生了变化，尤其是工件的下侧的晶粒变得均匀细小。焊接区的晶粒尺寸得到了细化。能够清晰分辨出热影响区和母材的分界。86175

在焊接过程中对底部进行散热，搅拌摩擦焊接头的性能也发生了显著的变化。随着旋转速度的增加，焊接的热输入变大，焊接接头的拉伸断裂位置多在热影响区处，断口呈现的断裂特征主要为韧性的韧窝。在对底部进行散热时转速为440rpm的条件下，搅拌摩擦焊接头获得了较高的焊接质量。由此可以得出结论，对BTFSW的底部散热是一种有效提高搅拌摩擦焊接接头的强度与韧性的工艺方法。

毕业论文关键词：BTFSW实验；底部散热；组织；焊接质量

Abstract Bobbin tool friction stir welding technology is an extension of the traditional stir friction welding technology and improvement, with green, without dust, without filling materials and so on。 In this paper, 8mm thick 6061 aluminum alloy by BTFSW is tested。 The torque of the welding process and weld zone temperature detection are analyzed。 The welding quality is analyzed by the metallurgical structure and hardness。 BTFSW was done in bottom cooling conditions to investigate the effect of weld condition on the mechanical property of different zone at the joint。 

Under the bottom cooling condition during the welding, the microstructure of the welding zone including welding nugget zone、thermal-mechanical affect zone and heat affect zone all have changed remarkably。 Especially the grain size of the upside of the work space is smaller。 The grain size of welding zone is smaller and we can see the obvious boundary between heat affect zone and base material。 

Under the bottom cooling condition during the welding, the property of bobbin tool friction stir welding joint has changed obviously。 With increasing spinning speed, the heat input has improved。 The heat affect zone is the space where the tensile fracture often occurred and the tensile fracture surface exhibit ductile fracture feature dominated by dimples。 Under the bottom cooling of the BTFSW, the welding joint has reached the higher welding quality with 440rpm。 In conclusion, the bottom cooling of bobbin tool friction stir welding is an efficient method for improving strength and toughness of the joint。

Keywords: BTFSW experiment；bottom cooling ；microstructure ；welding quality

目  录

第一章  绪  论 1

1。1 选题背景及意义 1

1。2 常规搅拌摩擦焊 2

1。2。1 常规搅拌摩擦焊的原理 2

1。2。2 常规搅拌摩擦焊的工艺特点 2

1。2。3 搅拌摩擦焊热过程分析 3

1。3 双轴肩搅拌摩擦焊 4

1。3。1 双轴肩搅拌摩擦焊的原理 4

1。3。2 双轴肩搅拌摩擦焊的特点 5

1。3。3 双轴肩搅拌摩擦焊热过程的研究现状