Effects of Different Heat Treatment Conditions on Fatigue Behavior of AA7075 Alloy

Abstract

AbstractIn this study, the effect of different heat treatment processes applied to AA7075 alloys on the fatigue behavior was examined. The processes applied to AA7075 aluminum included annealing (O), high temperature pre-precipitating (HTPP), artificial aging (T6), retrogression and re-aging (RRA). The annealing heat treatment was performed for 2 hours at 500°C and samples were cooled in the furnace. In the artificial aging (T6) process, after the samples were solution treated for 2 hours at 500°C, they were quenched at room temperature and aged for 24 hours at 120°C. In the retrogression and re-aging process, samples were solution treated for 1 hour at 220°C after the T6 process and then re-aged for 24 hours at 120°C. In the high temperature pre-precipitating, pre-precipitates were formed for 30 minutes at 450°C and then, it was aged for 24 hours at 120°C. All samples were characterized through the scanning electron microscope (SEM + EDS), hardness measurements and X-ray difraction (XRD) techniques. At the end of experimental studies, SEM and EDS examinations XRD results revealed that η (MgZn2) phase formed in the microstructure following the HTTP, RRA and T6 heat treatment processes. As a result of the fatigue tests, the highest fatigue strength was measured in samples treated with artificial aging (T6), the lowest fatigue strength was measured in the annealed (O) samples.