STUDIES ON FRICTION STIR WELDED AA 7075 ALUMINUM ALLOY

摘要

Friction stir welding is a promising solid state joining process and is widely being considered for aluminum alloys. In this work, the microstructural and corrosion properties of friction stir welded 7075 Al alloy were studied. The microstructures of the base metal, bore metal, thermo-mechanically affected zone (TMAZ) and weld region were characterized by optical microscopy and transmission electron microscopy. Micro-hardness profile was obtained across the weld. The pitting corrosion properties of the weldments were studied in 3.5 percent NaCl solution. Friction stir welding of this alloy resulted in fine recrystallized grains in weld nugget which has been attributed to frictional heating and plastic flow. The process also produced a softened region in the weld nugget, which may be due to the dissolution and growth of possible precipitates, identified as Mg_(32)(Al,Zn)_(49). Corrosion resistance of weld metal has been found to be better than that of TMAZ and base metal.