摘要本研究是基于超声辅助搅拌摩擦焊以及热管改善焊接温度场的研究思路，通过在焊接过程中施加热管对温度场进行主动控制，同时利用超声振动效应来达到改善焊接接头“弱连接”的目的。分别在常规条件、超声振动条件、热管/超声协同(空冷)以及热管/超声协同(常温水冷)四种条件下进行焊接，通过对比分析探究焊接接头弱连接的演变规律。86492

通过测温试验发现各测温点的温度均经历了一个先上升后下降的过程。同时与常规条件相比，其他三种施加主动控制的焊接温度场各阶段峰值温度均有下降，尤其在热管冷凝端采用常温水冷时温度下降最为明显。论文网

金相试验研究表明超声振动可以明显细化焊接接头的晶粒，焊核区均为细小的等轴晶。同时施加超声与热管时，尤其在水冷条件下，焊核区上部晶粒也明显得到细化。

硬度试验表明，显微硬度曲线为不对称“W”型分布，施加超声振动对焊核区硬度影响不大，但前进侧热机影响区的硬度明显提高。

拉伸试验表明，施加主动控制对焊接接头的抗拉强度无明显影响，但在单独施加超声振动时，对接头的塑性有较大的提升。

毕业论文关键词：AZ31镁合金；搅拌摩擦焊；超声振动；热管；温度场 

Abstract This study is based on the idea of the ultrasonic vibration friction stir welding and the heat pipe was used to control the temperature field。 In order to eliminate the phenomenon of weak link and improve the microstructure and property of AZ31 magnesium alloy joint by FSW, the ultrasonic vibration and heat pipe was applied to the welding process。 Respectively in friction stir welding, ultrasonic vibration condition, heat pipe/ultrasonic vibration (air cooling) and heat pipe/ultrasonic vibration (water cooling at room temperature), the FSW experiment were done。 Furthermore, the evolution of weak connection of FSW joints will be researched through contrastive analysis。 

The result of vibration measurement shows that each measurement point temperature goes through a process of first increasing and then decreasing。 Compared with the FSW, the peak temperature of welding process that imposed with active control had dropped, especially in the heat pipe with water cooling。

Microstructure analysis shows that ultrasonic vibration welding joint grains were fined apparently, especially in the nugget zone。 There are all the small equaled grains。 While Ultrasonic and heat pipe were applied together, especially in water conditions, the size of the grains in upper part of nugget zone is obvious refined。

Hardness test shows that the micro-hardness curve presents an asymmetric “W” type distribution。 There is no clear improvement for the nugget zone when applying ultrasonic vibration and heat pipe, however, the ultrasonic and heat pipe have an advantage effect to the hardness of the thermo-mechanical affected zone in advancing side。

The tensile test shows that there is no obvious effect on the tensile strength of welded joints in different conditions。 But the plasticity of the ultrasonic vibration joints was improved greatly。

Key words: AZ31Mg; Friction Stir Welding; Ultrasonic Vibration; Heat Pipe; Temperature Field

目  录

第一章 绪论 1

1。1选题的背景及意义 1

1。2搅拌摩擦焊的概述 2

1。2。1搅拌摩擦焊的原理 2

1。2。2搅拌摩擦焊接头显微组织及缺陷的研究 3

1。2。3搅拌摩擦焊的应用 5