Influence of Welding Speed on Microstructure and Mechanical Properties of 5251 Aluminum Alloy Joints Fabricated by Self-Reacting Friction Stir Welding

Abstract

In the present study, 8 mm-thick 5251 aluminum alloy was self-reacting friction stir welded (SRFSW) employing an optimized friction stir tool to analyze the effect of welding speed from 150 to 450 mm/min on the microstructure and mechanical properties at a constant rotation speed of 400 rpm. The results indicated that high-quality surface finish and defect-free joints were successfully obtained under suitable process parameters. The microhardness distribution profiles on the transverse section of joint exhibited a typical “W” pattern. The lowest hardness values located at the heat-affected zone (HAZ) and the width of the softened region decreased with increasing welding speed. The tensile strength significantly decreased due to the void defect, which showed mixed fracture characteristics induced by the decreasing welding speed. The average tensile strength and elongation achieved by the SRFSW process were 242.61 MPa and 8.3% with optimal welding conditions, and the fracture surface exhibited a typical toughness fracture mode.

Development of Al-Mg2Si Alloy Hybrid Surface Composites by Friction Stir Processing: Mechanical, Wear, and Microstructure Evaluation

“…The steady state is mirrored by equiaxed sub-grains with virtually dislocation-free interiors, constant sub-grain size, and sub-grain border misorientation, as shown in Figure 8. These low-angle boundaries evolve into high-angle boundaries during a continual dynamic recrystallization process, resulting in a fine-grained structure [61][62][63]. Regardless of composition, the extreme turbulence of the material in a semi-solid state around the pin causes the particles in the SZ to fragment [33,64].…”

Mechanical Property Improvement in Dissimilar Friction Stir Welded Al5083/Al6061 Joints: Effects of Post-Weld Heat Treatment and Abnormal Grain Growth

“…Given their moderate strength, commendable toughness features, and high corrosion resistance, Al5083 and Al6061 are ideal for applications related to the automotive industry and fabrication of marine structures, pipelines, and aircraft components [ 3 , 4 , 5 ]. Magnesium and silicon are the main alloying elements in the heat-treatable alloy Al6061, whereas magnesium is the only main alloying element in the strain-hardened alloy Al5083 [ 6 , 7 ].…”