Mechanical Properties and Tensile Failure Mechanism of Friction Stir Welded 2219-T6 and 5A06-H112 Joints

Abstract

Friction stir welding was employed to weld dissimilar 2219/5A06 Al alloys in this work. The influences of alloy positioning on the mechanical properties and fracture behavior of the joints were studied via fracture morphology observation and microstructural analysis. The results show that the difference in the plastic flow and thermal field in the welding process is caused by different basic material configurations, which results in the formation of a free strengthening phase zone and microstructural heterogeneity in the joint. The low-hardness texture component caused by the free strengthening phase zone and microstructural heterogeneity becomes crack initiation, and a crack tends to propagate along the grain boundaries. Finally, when the stronger 2219-T6 alloy was placed on the advancing side, the joints had better tensile properties. The average tensile strengths of the 2A5R and 5A2R joints can reach 79.8% (343 MPa) and 78.4% (337 MPa) of the 2219 base material, respectively.