Mechanism of 1561 Aluminum Alloy Weld Seam Strengthened by Using Microalloyed Wire

A novel mircoalloyed wire was prepared by adding Sc and Zr elements into the chemical composition of 1561aluminum alloy, then the TIG method was used to join 3 mm thick 1561 plate. Optical microscope, scanning electron microscope, X-ray diffractometer and transmission electron microscope were employed to characterize the microstructure of the weld, and the materials testing machine was utilized to test the tensile performance of the joints. The results show that equiaxed grain structure is formed in the 1561 TIG weld seam and the average grain size is 26.2 μm. All Mg atoms are dissolved into the weld with a solid solubility of 7.00at%. Al₃(Sc, Zr) precipitates in the weld seam is distributed near the grain boundaries and the average size is 10.8 nm. It is revealed that the contribution of precipitation strengthening to the yield strength reaches 17.7% through model calculation. The yield strength of 1561 TIG weld using microalloyed wire is 11.2%higher than that with 1561 wire.