Effect of post weld heat treatments on mechanical and stress corrosion cracking behaviour of Aa7075 friction stir welds

The high strength aluminium alloys exhibits low weldability due to poor solidification microstructure, porosity in the fusion zone and lose their mechanical properties when they are welded by fusion welding techniques. Friction stir welding (FSW) is a promising technique to retain the properties of the alloy as the joining take place in the solid state. Even though mechanical properties of the welds are better, corrosion resistance of welds gets affected by the microstructural changes that occur during welding. In the present work the effect of post weld treatments viz. peak ageing (T6), overaging (T73), retrogression and retrogression & reaging (RRA) on the mechanical properties and stress corrosion resistance is studied. It was observed that Retrogression and RRA treatments improved the resistance to stress corrosion cracking and maintained the mechanical properties. The resistance to stress corrosion is improved in RRA and Retrogression condition with the minimum loss of weld strength. This is attributed to the dissolution, re-precipitation and re-distribution of precipitates. © 2014 SERSC.