Abstract
The present study was focused on establishing guidelines for successful friction stir welding of Al alloys and Cu lap joints. Detailed investigations in respect to tool geometry, tool material, work-piece material, welding parameters, stacking sequence, and heat sink were carried out. The soundness of welded joints was tested through microscopic analysis and the lap shear test. The results revealed that the tungsten carbide (WC) tool with square-pin produced sound joints in terms of minimized defects and high strength. Further, the use of heat sink proved as an important pre-requisite when the stacking sequence was inversed (i.e., Cu-Al), and this stacking configuration in comparison with the Al-Cu stacking yielded weaker joints. The influence of the tool welding speed (F, mm/min) was found to depend upon the tool material. A range of tool welding speed (23.5–37.5 mm/min) worked well for the WC tool. However, only two values of welding speed (30 mm/min and 37 mm/min) were observed to be conducive when the tool material was HSCo (high-speed cobalt)-steel. Finally, it was concluded to employ the WC tool with square-pin, a welding speed of 30 mm/min, the rotational speed (S, rpm) of 1500 mm/min, and Al-Cu stacking sequence to successfully process the Al/Cu lap joints.
Highlights
Al-Cu bilayer sheet offers an attractive combination of high thermal and electrical conductivity and good corrosion resistance
The presented results can serve as a guideline to produce sound Friction stir welding (FSW) Al/Cu lap joints
Further tests were performed by varying the tool material (WC) as detailed in the coming section
Summary
Al-Cu bilayer sheet offers an attractive combination of high thermal and electrical conductivity and good corrosion resistance. Numerous conventional joining techniques such as brazing and laser welding are applied to join Al and Cu but it is challenging because of the difference in the physical and chemical properties of the metals and the tendency to form brittle intermetallic compounds (IMCs) during the formation of welded joints [3] These IMCs can impair the mechanical and electrical properties of the joint [4]. Luo et al [9] worked on numerical modeling of AA2A14-T6 to visualize the material flow during the FSW process They found that either high welding speed or low rotational speed could cause welding defects such as holes and cracks. Karimi et al [17] investigated the effect of tool material on the metallurgical and mechanical properties of dissimilar Al/Cu butt joints They found that the tool with low thermal conductivity produced better welded joints. The presented results can serve as a guideline to produce sound FSW Al/Cu lap joints
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