Abstract

In this paper, friction stir spot welding of 2-mm-thick AA 1060 Al to T2 Cu is conducted. The effects of dwell time, tool rotational speed and shoulder plunge depth on tensile shear failure load (TSFL) are investigated. A quadratic regression model is proposed to fit the relationship between TSFL of the joint and the welding process parameters. The analysis-of-variance results show that the rotational speed is the most significant factor affecting the TSFL. Joint fabricated at the low rotational speed is weak-bonded by discontinuous intermetallic layers due to the insufficient heat input. Increasing the rotational speed can improve the TSFL by promoting intermetallics formation at the interface, while an excessive increase in rotational speed results in formation of microcrack at the interface, which seriously compromises the tensile property of the joint. Shoulder plunge depth, tool rotational speed and dwell time of 0.1 mm, 2371 r/min and 4.96 s, respectively, were identified as the optimal combination of welding process parameters. Results of microstructure characterization show that the joint produced at the optimized process parameters is well metallurgically bonded by a 1.9-μm-thick laminated intermetallics layer which comprises CuAl and CuAl₂ sublayers. Result of fracture path reveals that the fracture firstly extends along the interfacial CuAl₂ layer by a brittle mode and then propagates through the aluminum matrix in the stir zone by a ductile mode.

中文翻译：

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铝/铜异种搅拌摩擦点焊的统计和冶金分析

摘要

本文对2mm厚的AA 1060 Al与T2 Cu进行了摩擦搅拌点焊。研究了停留时间，工具转速和肩突深度对拉伸剪切破坏载荷（TSFL）的影响。提出了二次回归模型来拟合接头的TSFL和焊接工艺参数之间的关系。方差分析结果表明，转速是影响TSFL的最重要因素。低速制造的接头由于热量输入不足而被不连续的金属间层弱结合。增加转速可以通过促进界面处金属间化合物的形成来改善TSFL，而转速的过度增加会导致界面处形成微裂纹，这严重损害了接头的拉伸性能。肩突深度，工具转速和停留时间分别为0.1 mm，2371 r / min和4.96 s被确定为焊接工艺参数的最佳组合。显微组织表征的结果表明，在最佳工艺参数下产生的接头通过1.9μm厚的层压金属间化合物层（包括CuAl和CuAl）良好地冶金结合₂个子层。断裂路径的结果表明，断裂首先以脆性模式沿界面CuAl ₂层延伸，然后以延性模式传播至搅拌区中的铝基体。