Gas tungsten arc welding of 7075 aluminum alloy: microstructure properties, impact strength, and weld defects

Precipitation-hardened 7075 (Al-Zn-Mg-Cu) aluminum alloys have low specific density and high strength. Because of these advantages, they are commonly used as construction materials in the aerospace industries. Even though they have such important and common areas of usage, their weldability is quite difficult. It is important to weld this alloy used in these industrial areas. In this study, 3 mm-thick 7075-T651 aluminum alloy materials were joined using different welding currents via gas tungsten arc welding (GTAW) method. The metallographic examinations were carried out to determine macrostructural and microstructural properties of the weld zones. Also, notch impact and hardness tests were performed to determine the mechanical properties of the welded samples. The results obtained as a result of the tests were evaluated and interpreted. The grain size of the weld center increased due to heat input occurring with increase of the welding current. Micro cracks (hot cracking) occurred in the roots of welding seams. The increase in the welding current affected the hardness distribution of the weld zone. The impact strength of the welded sample was negatively affected by the grain coarsening and micro cracks in the welding seam.