Creep lifetime of Al 6061-T6 pressurized rotating friction stir welded tube subjected to internal pressure and rotational velocity: Welding and creep lifetime optimization

Abstract

Aluminum 6061-T6 alloys have numerous applications in the industry due to their unique properties such as higher corrosion resistance and strength-to-weight ratio. Friction stir welding is also a technique that can be used in aluminum joints because of its numerous advantages. In this paper, optimum friction stir welding parameters that lead to a higher failure load are obtained using tensile test data and analysis of variance technique. According to the analysis of variance results, it is found that the tool rotational speed has a major effect among the welding parameters on the failure load. Then, creep tests are carried out on non-welded and welded specimens to predict their creep behavior. The Norton power law equation is used as a creep constitutive equation to model the creep behavior of the specimens. The model is used to predict the creep lifetime of the welded and non-welded rotating pressurized vessels. The results show that an optimally welded vessel can only sustain up to 0.75 of pressure for the non-welded vessel with the same rotating speed. Since this comparison is not straightforward because of the number of affecting parameters. Hence, the reference stress method is used to produce a set of diagrams that provide design conditions and optimum creep lifetime for the friction stir welded Al 6061-T6 rotating pressurized vessels.