摘要：6061铝合金一直都是各个工业领域应用最广泛的轻型结构材料之一。静止轴肩搅拌摩擦焊（SSFSW）是在常规搅拌摩擦焊基础上发展起来的一种新型的固相连接技术，得到的焊接接头表面光滑，减薄量小，且无常规搅拌摩擦焊中出现的飞边、毛刺、隧道、孔洞等缺陷。目前学术界关于静止轴肩搅拌摩擦焊的研究仍处于探索阶段，因此对静止轴肩搅拌摩擦焊的工艺研究具有十分重要的意义。

本论文采用静止轴肩搅拌摩擦焊的方式对板厚为5mm的6061-T6铝合金进行对接焊，在焊接工艺参数优化的基础上，探索了其对焊接接头的形貌、组织和力学性能的影响。结果显示：静止轴肩搅拌摩擦焊焊接接头表面成形光滑且无缺陷，前进侧焊核区和热机影响区分界线十分明显，整个焊接接头呈轴对称的特点。在拉伸试验中，焊接速度对接头的抗拉强度影响较大，而主轴的旋转速度对接头的抗拉强度无明显的影响，接头属于准解理断裂。焊接接头的显微硬度曲线呈“W”形，焊核区的硬度约为母材的70%。接头组织方面，焊核区为细小的等轴晶，热机影响区的晶粒被拉长，呈长条状，热影响区由于焊接热循环的作用而使晶粒粗化，是整个焊接接头最薄弱的区域。

关键字静止轴肩；6061铝合金；宏观形貌；微观组织；力学性能

Abstract：6061 Aluminum alloy has always been one of the most widely used lightweight structural material in various fields of industry. Stationary Shoulder Friction Stir Welding (SSFSW) is a new kind of solid state welding technology which is developed on the basis of conventional friction stir welding, the joint has smooth welds and little thickness reduction, in particular, there will be no defects in welded joint like conventional friction stir welding. So far, there is no authoritative conclusion in academic,the research  of SSFSW is still in the exploratory stage. So it is significant for us to study the process of SSFSW.

In this paper, 5mm thick 6061-T6 aluminum alloy is selected as the experiment object. By changing the welding parameters to study the influence of the welding process on welding morphology,microstructure and mechanical properties of the joint. Under the reasonable welding parameters,the joint of Stationary Shoulder Friction Stir Welding (SSFSW) has smooth welds and no defects.The boundary between nugget zone(NZ) and thermo-mechanically affected zone(TMAZ) in advantage side is very obvious,the entire welded joint is axially symmetrical.At the result of tensile test,the welding speed has a great influence on the tensile strength of the joint, and the rotation speed of the spindle has no obvious effect on the tensile strength of the joint,the joint belongs to quasi-cleavage fracture.The micro-hardness curve of the joint assumes “W” shapes,the hardness of nugget zone(NZ) reaches 70% of base metal zone(BM).In terms of microstructure, nugget zone(NZ) has Fine equiaxed grains,the grains in thermo-mechanically affected zone(TMAZ) were elongated to strip shape,due to the thermal cycling,the grains in heat affected zone(HAZ) is coarsened,HAZ is the weakest area of the entire welded joint.

Keyword Stationary shoulder；6061 aluminum alloy；Macroscopic  morphology； Microstructure；Mechanical property

目录

第1章 绪论 1

1.1选题背景及意义 1

1.2静止轴肩搅拌摩擦焊 2

1.2.1静止轴肩搅拌摩擦焊焊接原理 2

1.2.2静止轴肩搅拌摩擦焊焊接工具 3

1.2.3静止轴肩搅拌摩擦焊焊接特点