An Investigation on Effect of Filler Metal on Microstructure and Tensile Strength in GTAW Welding of 7075-T651 Aluminum Alloy

Aluminum alloys have received much attention in fabrication of lightweight structures, especially in aerospace and automotive applications due to their high strength to weight ratio. In some cases, manufacturer shall join some components by welding processes due complicated design of structure. In this study, effect of filler metal (ER 4043, ER 4047, ER 5183 and ER 5356) on transverse tensile strength and microstructure of 7075-T651 Aluminum alloy has been investigated. Plates were received in T651 condition and were cut to 300*150*3 mm3. Single V-groove was prepared for gas tungsten arc welding in pure Argon environment. Care was taken to prevent distortion of plates during welding. Transverse tension test and metallographic samples were extracted by waterjet cutting from weldments based on ISO 15614 standard. More detailed microstructural and fracture surfaces observations were performed by scanning electron microscope. Metallographic observations showed in all samples, coarse grains of aluminum solid solution are formed in weld metal. Electron microscope observations revealed microsegregation of alloying elements at final surfaces of solidification. Tension test results showed using different filler metals can increase weldment transverse tensile strength by 40%. Increment of weld metal tensile strength was attributed to presence of strengthening alloying elements in solid solution and less microsegregation of alloying elements. According to all observations, it was finally concluded filler metal has significant effects on transverse tensile strength and microstructure of AA7075-T651 weldment.

کلیدواژه ها:

7075-T651 Aluminum alloy ، Welding ، Filler metal selection ، Tensile strength