Corrosion Analysis of Friction Stir-welded AA 7075 Aluminium Alloy

Abstract

Friction stir-welding of AA7075 has become widely practiced in the fabrication of light-weight structures requiring high strength-to-weight ratios and superior corrosion resistance.The friction stir-welding (FSW) process and tool parameters play a key role in determining the joint's characteristics.In this paper, the corrosion resistance of a friction stir-welded alloy was studied via polarization and electrochemical impedance spectroscopy in 3.5% NaCl.The microstructure of different positions along the thickness of the aluminium alloy plate has been investigated with regard to varying parameters, including rotary speed and transverse speed.The heat-affected zones of the weld exhibited the highest susceptibility to inter-granular corrosion.The results also show that sound joints in AA7075 can be achieved using friction stirwelding.Corrosion resistance decreases with the increase of traverse speed from 0.37 to 0.76 mm/s at a rotary speed of 800 rpm.Corrosion resistance at a rotary speed of 1000 rpm is lower than that at 1200 rpm; an increase in the corrosion resistance may also be reached via the breaking down and dissolution of the inter-metallic particles.