Thermoelasticity for the evaluation of fatigue behavior of 7005/Al 2O 3/10p metal matrix composite sheets joined by FSW

Abstract

The advantages of the Friction Stir Welding process compared to conventional fusion welding technologies have been clearly demonstrated in recent years. In this study, the metal matrix composite under investigation was a 7005 aluminium alloy reinforced with 10% of alumina particles Friction Stir Welded by employing a tool rotating speed of 600 rpm and a welding speed of 250 mm/min. The optical and scanning electron microscopy observations performed on the different zones of FSW joints cross-section revealed the different structures of the nugget, the thermo-mechanical affected zone and the heat affected zones thanks to the difference due to the strong grain refinement produced by the dynamic recrystallization acting during the severe plastic deformation to which the material is subjected during welding. Only a few data are available in the literature on the fatigue behavior of these materials. Thermoelastic stress analysis (TSA) was applied to the study of the damage behavior in Friction Stir Welded MMC sheets, during fatigue tests. Fatigue tests were carried out under pulsating ( R = σ min/ σ max = 0–0.1), tension loading using a resonant electro-mechanical testing machine (TESTRONIC TM 50 ± 25 KN by RUMUL (SUI)). All the mechanical tests were performed up to failure which occurred at the interface with the welded area. The TSA measurement system allowed crack evolution to be observed in real-time during fatigue cycles and stress fields to be derived on the specimens from the temperature variation measured.