摘要：采用不同的焊接参数研究了17mm的7A52厚板铝合金焊缝组织以及接头的综合性能。结果表明，在搅拌头旋转速度500r/min，焊接速度为150mm/min时所得到的接头硬度较高，抗拉强度较低。当焊接速度提升到200mm/min时，焊缝会因为填充速度不足而形成孔洞缺陷。而搅拌头的旋转速度降低为400r/min时，硬度有些许降低，但是抗拉强度较高。通过观察金相的方式，发现在搅拌头旋转速度500r/min，焊接速度为150mm/min时依然存在着未焊透缺陷。在接头前进侧与后退侧组织存在显著不同。前进侧组织粒状晶粒与纤维状晶粒的分界面明显，而后退侧则体现为渐变，没有明显的晶界。焊接缺陷缺陷大多聚集于前进侧的组织。在前进侧基本的问题是塑性的焊缝金属回流能否顺畅，而后退侧更多的是焊缝金属的填充效率能否跟上焊接速度。并且这与搅拌头的压入深度也存在的一定的关系，因为压入深度直接影响到焊缝上层表面组织的形貌以及底部材料的塑性。通过拉伸试验，结果显示在搅拌头旋转速度400r/min，焊接速度为150mm/min时的焊接接头的抗拉强度最高。显微维氏硬度试验的结果表明7A52铝合金在500r/min的旋转速度下焊缝的性能更加优异，三个接头试样的硬度曲线都体现出W形。在热影响区的组织硬度会有所下降，但焊核区域硬度依然较高。综合考虑，搅拌头旋转速度与焊接速度的比值具有重要意义。这个比值为3.3时，焊缝表面成形好，但是存在底部未焊透的裂纹状缺陷。当比值降为2.5时，焊缝表面出现沟槽，并出现孔洞缺陷。

关键词 7A52铝合金搅拌摩擦焊焊接参数焊缝性能

毕业设计说明书外文摘要

Title Research on Friction Stir Welding Process of High Strength Aluminum Alloy Plate         

Abstract：The performance of the joints of 17mm 7A52 thick aluminum alloy welds were studied under different welding parameters. The results show that the hardness of the joint is higher when the rotational speed of the tool is 500r/min and the welding speed is 150mm/min, and the tensile strength is low. When the welding speed increased to 200mm/min, the weld will have not enought filling speed and form holes defects. And the rotation speed of the tool is reduced to 400r/min, the hardness is slightly reduced, but the tensile strength is high. It was found that there was still defects when the rotation speed was 500 r/min and the welding speed was 150 mm/min. There was a significant difference between the advancing side and retreating side. The interface between the grain-like grains and the fibrous grains of the advancing side is obvious, while the retreating side is reflected as a gradient, and there is no obvious grain boundary. Most of the weld defects are gathered on the advancing side of the organization. The basic problem with the advancing side is whether the plastic weld metal can return smoothly, and the retreating side is whether the weld metal filling efficiency can keep up with the welding speed. And this has a certain relationship with the press-in depth of the tool, since the press-in depth directly affects the topography of the surface of the weld and the plasticity of the bottom material. The tensile test showed that the tensile strength of the welded joint was the highest when the tool speed was 400r/min and the welding speed was 150mm/min. Finally, the results of the micro-Vickers hardness test show that the performance of the welds of 7A52 aluminum alloy is more excellent at 500r/min rotation speed, and the hardness curves of the three joints are W-shaped. The hardness will decrease in the heat affected zone, but it is still high in the welding  core area. It is important to consider the ratio of the rotation speed of the tool to the welding speed. When this ratio is 3.3, the weld surface is formed well, but there is crack-like incomplete root penetration at the bottom. When the ratio is reduced to 2.5, the weld has surface groove, while there are hole defects.  高强铝合金厚板搅拌摩擦焊接工艺研究:http://www.chuibin.com/huaxue/lunwen_205366.html