Experimental study on TIG full welding and single pass welding quality of 6061-T6 aluminum alloy sheet

Abstract

6061-T6 aluminum alloy plate (3 × 150 × 300 mm3) was welded by tungsten inert gas (TIG) welding. The welding process methods are single-pass welding process and full welding process respectively. The effects of different welding processes on the performance of TIG welding 6061-T6 aluminum alloy were compared and studied. The effects of microstructure and precipitation on the microhardness and tensile strength were analyzed by optical microscope, scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS) characterization, electron backscattering diffraction (EBSD) characterization, microhardness and tensile test. The microstructure of the weld zone is mainly composed of aluminum solid solution (α-Al) dendritic structure and Al–Si eutectic structure. Through EBSD characterization analysis, the average grain size of the weld zone of the full welding process and the single-pass welding process is about 45 μm and 55 μm, and the grain size of the heat-affected zone and the weld zone of the two welded joints does not change significantly. The hardness curves of the two welded joints have the same distribution trend, which is roughly 'W' type distribution. In the tensile test, the tensile strength of the single pass welding process is lower than that of the full welding process, and the fracture of the tensile parts is dimple structure, which is ductile fracture. Through analysis and comparative study, the full welding process is better than the single-pass welding process when welding 6061-T6 aluminum alloy sheet.

Keywords

• 6061-T6 aluminum alloy
• TIG
• Single-pass welding
• Full welding
• Microstructure
• Mechanical properties