Effect of Post Weld Heat Treatments on Mechanical and Stress Corrosion Cracking Behaviour of Aa7075 Friction Stir Welds

P. Vijaya Kumar, G. Madhusudan Reddy, K. Srinivasa Rao
2014 International Journal of u- and e- Service, Science and Technology  
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
more » ... 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. Copyright ⓒ 2014 SERSC 259 Stress corrosion Cracking Tests Stress corrosion cracking tests were conducted on constant load type SCC testing setup as per ASTM E-8/E8M-09 standards. The load applied on the test specimens were based on tensile test results is presented in the Table 3 .4.1. Specimens were immersed in a 3.5 wt. % NaCI solution (pH 6.5-7.0) and the solution was periodically circulated to maintain a constant pH. The loading arrangement of specimens is shown in the Figure 3 .4.1. The load applied and the time to failure is recorded for each specimen and is represented in the Table 3 .4.1. The SCC tests revealed that the as welded specimen has poor resistance to stress corrosion. The RRA and retrogression specimens had shown good resistance to stress corrosion. The time to failure for the specimen under retrogression treatment was 184 days, which maximum when compared to other post weld treated specimens.
doi:10.14257/ijunesst.2014.7.4.23 fatcat:hqpj2kns6bf2ti6l3tr4x6d5au