الفهرس 
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Abstract
In order to achieve superior properties for Al-Cu joints, researchers have studied various process parameters. The focus of the current experimental study was on the influence of pin geometry on the micro-structural and mechanical characteristics of these joints. During the experiment, an aluminum sheet was welded to a copper sheet using a constant rotational speed of 1280 rpm and a traverse speed of 16 mm/min. The welding tool used was made from W302 steel and had four different pin profiles: straight cylindrical, tapered, triangular, and squared, all with flat shoulders. This allowed for an examination of the effect of pin shape on the joint. Additionally, four tools with squared pins and different shoulder shapes (flat, scroll, convex, and concave) were used to evaluate the effect of shoulder shape on the joint.
The results showed that when the squared pin was used, it produced the optimum joint with a defect-free structure and a tensile strength of 107.2 MPa (80% of the aluminum strength). On the other hand, when the pin with a triangular profile was used, it resulted in lower quality characteristics with dislocations, separations, and cracking observed in copper particles inside the aluminum matrix. The micro hardness trend is consistent across all specimens. Moreover, specimens welded using squared and cylindrical pin tools have the maximum hardness values obtained at the stir zone of the copper side. There is a slight improvement in the tensile strength produced when the concaved shoulder is used instead of a flat shoulder, with the ultimate tensile strength reaching 110 MPa. Furthermore, a superior microstructure was obtained for the squared pin with a concaved shoulder case. In contrast, poor microstructure with many defects was noticed in the case of squared pin and scrolled shoulder case. The inspection of fractured surfaces showed well mixing between aluminum and copper as well as ductile fracture when a squared pin tool was used, while it showed a combination of ductile fracture and brittle fracture for the specimen welded with a triangular pin tool. As for the shape of the pin, the improvement rates were Taper 60%, Square 80%, Cylindrical 41%, and Triangle 22% of the base metal but for the shape of the shoulder, the improvement rates were concave. Square 84%, convex- Square 76% and Scroll- Square 65% and Flat -Square 80% of the base metal. Based on this study, the use of the squared pin tool gives the most favorable results compared to other pin profiles.