铝钢搅拌摩擦搭接接头力学性能及组织特征研究-材料工程专业毕业论文.docxVIP

哈尔滨工业大学工学硕士学位论文 哈尔滨工业大学工学硕士学位论文 万方数据 万方数据 两道焊缝的界面区并未重叠，界面区钩状结构、夹杂物以及叠层组织明显减 小。力学性能分析发现：当偏移距离分别为 5.8 mm 和 8.0 mm 时，接头的最 大拉剪载荷分别提高了 35.5%和 56.8%，当偏移距离为 8.0 mm 时，断裂位置 由界面区转移到上层铝合金的两热影响区交界处，这是由于双道焊缝的热影 响区相互叠加，热影响区变得薄弱，同时由于界面区的有效结合面积增加和 组织形貌得到优化所致。 设计并研制了新型的搅拌头，接头的有效承载面积增加 ，同时接头中缺 陷减少，所得焊缝的拉剪载荷增加了 37%，断口位置及形貌并没发生变化。 关键词：搅拌摩擦搭接；铝/钢；力学性能；界面特征；金属间化合物 II Abstract Aluminum alloys with low density and high specific strength a re prone to a substitute of steel in automobile industry for fuel efficiency and energy conservation. The reliable joints of Al/Steel are needed to satisfy the development of automobile industry. However, the joining technologies of these two materials are limited due to their different physical and thermal properties. Brittle intermetallic compounds (IMCs) were easily formed during the welding process which seriously affected the durability of the joint. Recently, friction stir lap welding (FSLW) of Al/steel has been becoming a research hotspot. In this thesis, AA6082-T6 and QSTE340TM steel were friction stir lap welded in this paper to investigate its joint microstructures, mechanical properties and the formation mechanism of IMCs, and reveal the relationship between microstructure, IMC and mechanical property. With pin length of 2.9mm, 3.1mm, 3.3mm and process parameters as the tilt angle of the rotating tool with respect to the vertical axis of the aluminum plate of 2.5 degree, the shoulder plunge depth of 0.2mm, the rotating speed of 1000rpm and the traverse speed of 50mm/min, defect-free FSLW joints were obtained. The pin length of tools has a significant effect on mechanical property of Al/steel friction stir lap welded joint, with the pin length of 3.1mm, the failure load can reach 5233N, much higher than that of 2.9mm and 3.3mm. The failure locations were all located at the interface region of the lap joints , fracture reveals dissociation. This results were analyzed as follows: effective bearing area and the microstructure of IZ determines the