6082-T6铝合金搅拌摩擦焊接头微观组织及力学性能的研究

发布时间：2017-12-31 11:32

本文关键词：6082-T6铝合金搅拌摩擦焊接头微观组织及力学性能的研究　出处：《吉林大学》2015年硕士论文　论文类型：学位论文

【摘要】：6082-T6铝合金具有较高的比强度、优异的耐蚀性和挤压性能,被广泛应用于轨道车辆生产领域。铝合金熔化焊存在的主要问题是易产生气孔、热裂纹,且接头强度降低。搅拌摩擦焊(FSW)是一种新的固相连接方法,有利于解决铝合金熔化焊存在的问题。但目前国内外关于6082-T6铝合金中厚板FSW的研究相对较少。因此,本文主要针对10mm厚6082-T6铝合金板进行了FSW试验,系统地研究了FSW接头的温度场、组织演变、力学性能特点及焊接工艺参数的影响规律,并且在试验的基础上建立了搅拌摩擦焊过程的热源模型,利用ANSYS软件对焊接过程动态温度场进行了模拟,并对比分析了实测与模拟预测的结果。研究结果表明,距离焊缝中心线越近,焊接热循环峰值温度越高,对接头微观组织及力学性能的影响越加明显。6082-T6铝合金FSW接头包括：焊核区(NZ)、热机影响区(TMAZ)、热影响区(HAZ)和母材区(BM)。母材区的微观组织主要由α-Al和β"(Mg5Si6)相组成；焊核区主要为细小α-Al等轴晶,并存在点状的GP区；热机械影响区中的晶粒呈现被拉长的畸变特征,并产生高密度的位错,这些位错的存在提高了该区的硬度；热影响区的晶粒明显粗化,原始的β”相在焊接过程中转变为β’相。显微硬度测量结果表明,FSW接头横向硬度分布近似为W型,最低硬度值出现在前进侧紧邻TMAZ的HAZ。NZ上部的硬度高于NZ下部的硬度。接头的显微硬度值在焊缝中心两侧的分布趋势基本对称,但后退侧的显微硬度值高于前进侧。拉伸试验结果表明,FSW接头的抗拉强度达到母材强度的70%以上,接头断裂主要发生在前进侧紧邻TMAZ的HAZ。研究发现,FSW过程中的焊接速度和旋转速度对接头温度场、组织演变及力学性能具有一定的影响。随着焊接速度的降低或者旋转速度的增加,焊接热输入增加,焊核区、热机械影响区和热影响区的晶粒粗化,紧邻TMAZ的HAZ硬度有降低的趋势。在本试验条件下,适当增加焊接速度、降低旋转速度有利于改善接头的力学性能。采用ANSYS有限元模拟软件对FSW接头温度场进行了模拟分析。模拟得到的焊接热循环曲线与实测热循环曲线基本吻合。本研究结果为优化FSW参数改善接头力学性能提供了必要的理论依据和试验数据。
[Abstract]:6082 - T6 aluminum alloy has high specific strength , excellent corrosion resistance and extrusion performance , and is widely used in the field of rail vehicle production . The main problems existing in the melting welding of aluminum alloy are easy to generate air holes , hot cracks and lower joint strength . The results show that the closer the center line of the weld seam , the higher the peak temperature of the welding heat cycle , the more obvious the effect of the welding heat cycle peak temperature on the microstructure and mechanical properties of the joint . The microstructure of the HAZ is mainly composed of 伪 - Al and 尾 " ( Mg5Si6 ) . The microhardness of the HAZ is higher than that of the lower part of NZ . The microhardness of the joint is higher than that of the lower part of NZ . The tensile test results show that the tensile strength of the FSW joint reaches over 70 % of the strength of the base material . The fracture of the joint mainly occurs in HAZ of the forward side close to TMAZ . It is found that the welding speed and the rotating speed in the FSW process have some influence on the temperature field , microstructure evolution and mechanical properties of the joint . As the welding speed decreases or the rotation speed increases , the welding heat input increases , the HAZ hardness of the welding nuclear area , the thermal mechanical influence area and the heat affected zone is reduced . Under the condition of this test , the welding speed is increased properly , and the rotating speed is reduced to improve the mechanical property of the joint . The temperature field of FSW joints is simulated by ANSYS finite element simulation software . The simulated welding thermal cycling curve is basically in agreement with the measured thermal cycling curve . The results of this study provide the necessary theoretical basis and experimental data for optimizing the mechanical properties of FSW parameters .

【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG453.9

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