Weldability, microstructure, and residual stress in Al/Cu and Cu/Al friction stir spot weld joints with Zn interlayer
Weldability, microstructure, and residual stress in Al/Cu and Cu/Al friction stir spot weld joints with Zn interlayer
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DOI：
10.1007/s00170-020-06202-z
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发表时间：
2020-10
期刊：
影响因子：
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通讯作者：
A. Boucherit;S. Abdi;M. Aissani;B. Mehdi;K. Abib;R. Badji
中科院分区：
文献类型：
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作者：
A. Boucherit;S. Abdi;M. Aissani;B. Mehdi;K. Abib;R. Badji
研究了搭接形式和锌层间添加对Al/Cu（形态#1）和Cu/Al（形态#2）搅拌摩擦点焊（FSSW）显微组织、残余应力状态和质量的影响。研究表明，焊缝质量与销长和锌添加量密切相关。插针深度越高，得到的抗拉抗剪强度越大。Zn的加入明显降低了Al2Cu层的厚度（从10 μm减小到2 μm），有利于al4.2 cu3.2 zn0.7相的形成，从而阻碍了有害al4cu9化合物的形成。材料流分析表明，在形貌#1的焊缝界面处存在一个包含薄的连续金属间层（约2.07 μm）的混合区。同时，Cu材料被Zn层覆盖，在搅拌区硬度增加（228 HV）。抗拉剪切强度从1650 N显著提高到3600 N（提高率约为118%）。相反，在形态#2中，Zn箔被挤出点焊界面，导致材料无混杂，金属间层不连续，硬度水平较低（140 HV），抗剪强度提高率较弱（≈53%）。层间添加Zn后，残余应力呈准对称分布，由+ 60 MPa的拉应力转变为−10 MPa的压应力。
In this work, the effect of lap joint configuration and Zn interlayer addition on the microstructure, the residual stress state, and the quality of Al/Cu (configuration #1) and Cu/Al (configuration #2) friction stir spot welds (FSSW) was investigated. The study revealed the close dependency of the weld joint quality on the pin length and Zn addition. The higher the pin plunge depth is, the greater the obtained tensile shear strength. The Zn addition reduced sensibly the thickness of Al2Cu layer (from 10 to 2 μm) and favored the formation of the Al4.2Cu3.2Zn0.7precipitate that hindered the formation of detrimental Al4Cu9compounds. Material flow analysis revealed the presence of an intermixing zone containing thin continuous intermetallic layer (approximately 2.07 μm) at the weld interface of configuration #1. Meanwhile, the Cu material was covered by the Zn layer, which resulted in a hardness increase (228 HV) at the stirred zone. In addition, a significant increase of the tensile shear strength from 1650 to 3600 N was noticed (an improvement rate of ≈ 118%). Conversely, in configuration #2, the Zn foil was squeezed out of the spot weld interface resulting in the absence of material intermixing, discontinuous intermetallic layer, low hardness level (140 HV), and weak improvement rate of the shear strength (≈ 53%). The Zn interlayer addition resulted in a quasi-symmetric distribution of the residual stresses and shifted their nature from tensile stresses (+ 60 MPa) to compressive ones (− 10 MPa).