In this study, the effect of Friction Stir Welding on a 6061 aluminium alloy reinforced with 20% of alumina particles metal matrix composite was analysed. The sheets were joined by employing a tool rotating at a speed of 700 RPM and a welding speed of 250 mm/min. Optical and scanning electron microscopy observations performed on different zones of the FSW joints cross section revealed the different nugget structures: the thermo-mechanical affected zone and the heat affected zones thanks to the difference in reinforcing particles dimensions as a consequence of the friction process. After FSW the material was aged in a 3.5% NaCl + 0.3 g/l H2O2 solution for 1, 10 and 90 days. Being a non-contact technique and allowing real-time analysis unlike most investigating means used in this field, the thermoelastic stress technique was applied with success to the study of crack formation and propagation of friction stir welded MMC sheets during cyclic fatigue tests. Fatigue tests were carried out under the axial total stress-amplitude control mode with R=σmin/σmax = 0.1 using a resonant electro-mechanical testing machine (TESTRONICTM 50± 25 KN by RUMUL. SUI). All the mechanical tests were performed on as-FSW and aged samples up to failure. The TSA measurement system allowed crack evolution to be observed in real-time during fatigue cycles and the stress fields to be derived on the specimens directly from the measured temperature variations.
Thermoelasticity for the evaluation of fatigue behaviour of 6061/Al 2O3/20p metal matrix composite sheets joined by FSW
MORETTI, MICHELE;ROSSI, Gianluca
2007
Abstract
In this study, the effect of Friction Stir Welding on a 6061 aluminium alloy reinforced with 20% of alumina particles metal matrix composite was analysed. The sheets were joined by employing a tool rotating at a speed of 700 RPM and a welding speed of 250 mm/min. Optical and scanning electron microscopy observations performed on different zones of the FSW joints cross section revealed the different nugget structures: the thermo-mechanical affected zone and the heat affected zones thanks to the difference in reinforcing particles dimensions as a consequence of the friction process. After FSW the material was aged in a 3.5% NaCl + 0.3 g/l H2O2 solution for 1, 10 and 90 days. Being a non-contact technique and allowing real-time analysis unlike most investigating means used in this field, the thermoelastic stress technique was applied with success to the study of crack formation and propagation of friction stir welded MMC sheets during cyclic fatigue tests. Fatigue tests were carried out under the axial total stress-amplitude control mode with R=σmin/σmax = 0.1 using a resonant electro-mechanical testing machine (TESTRONICTM 50± 25 KN by RUMUL. SUI). All the mechanical tests were performed on as-FSW and aged samples up to failure. The TSA measurement system allowed crack evolution to be observed in real-time during fatigue cycles and the stress fields to be derived on the specimens directly from the measured temperature variations.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
