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Influence of welding parameters on the microstructure, thermal fields and defect formation in AA7075-T6 friction stir welds
Welding in the World ( IF 2.1 ) Pub Date : 2020-04-02 , DOI: 10.1007/s40194-020-00869-4
D. Ambrosio , V. Wagner , C. Garnier , D. Jacquin , A. Tongne , M. Fazzini , O. Cahuc , G. Dessein

This study focuses on the influence of the welding parameters on defectiveness, thermal field and grain size in friction stir welding of aluminium alloy 7075-T6. Different welded specimens were produced employing various rotational speeds and welding speeds. In the first part of the analysis, the quality of the joints was evaluated by microscopic observation of the jointed cross-sections to investigate the modification of the shape of the stirred zones and the occurrence of internal voids. Afterwards, temperature and grain size of welds obtained at welding speed of 60 mm/min have been measured to study the influence of the rotational speed on the heat input. Temperature measurements have been carried out with thermocouples and infrared camera. Grain size evolution of the material was analysed by optical observations of the jointed cross-sections and the average grain size in the nugget zone (NZ) has been estimated through electron backscatter diffraction. The results globally show that the first internal defects arose at the same time as an unexpected zone on the advancing side between the shoulder affected zone (SAZ) and NZ. In sound welds, from 800 to 1400 rpm, the peak temperature showed an increase between 5 and 15%, depending on the considered zone, while the grain size in the stirred zone increased from 2 to 3.6 μ m. Overall, it has been shown that the approach to the defective condition is due to the low heat input which is responsible for improper material flow during the process.

中文翻译:

焊接参数对AA7075-T6搅拌摩擦焊缝的组织,热场和缺陷形成的影响

本研究着重于7075-T6铝合金搅拌摩擦焊接参数对缺陷,热场和晶粒尺寸的影响。使用不同的旋转速度和焊接速度生产出不同的焊接试样。在分析的第一部分中,通过显微镜观察接缝的横截面来评估接缝的质量,以研究搅拌区形状的变化和内部空隙的发生。然后,测量以60 mm / min的焊接速度获得的焊缝的温度和晶粒尺寸,以研究转速对热输入的影响。温度测量已通过热电偶和红外热像仪进行。通过光学观察接缝的横截面来分析材料的晶粒尺寸演变,并通过电子反向散射衍射估算了熔核区(NZ)的平均晶粒尺寸。总体结果表明,第一个内部缺陷与肩部受影响区域(SAZ)和NZ之间的前进侧意外区域同时出现。在健全的焊缝中,从800 rpm到1400 rpm,峰值温度显示增加5%至15%,具体取决于所考虑的区域,而搅拌区域的晶粒尺寸从2增加至3.6 总体结果表明,第一个内部缺陷与肩部受影响区域(SAZ)和NZ之间的前进侧意外区域同时出现。在健全的焊缝中,从800 rpm到1400 rpm,根据所考虑的区域,峰值温度显示增加5%至15%,而搅拌区域的晶粒尺寸从2增加到3.6 总体结果表明,第一个内部缺陷与肩部感染区(SAZ)和NZ之间前进侧的意外区域同时出现。在健全的焊缝中,从800 rpm到1400 rpm,根据所考虑的区域,峰值温度显示增加5%至15%,而搅拌区域的晶粒尺寸从2增加到3.6μ微米。总的来说,已经表明,接近不良状态的原因是低的热量输入,这导致在处理过程中材料流动不当。
更新日期:2020-04-02
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