Effects of Re-Aging on the Fatigue Properties of Aluminum Alloy AA7075

Abstract

AbstractIn this study, 7075 aluminum alloy was subjected to triple-aging of retrogression and re-aging (RRA) treatments. The alloy was retrogressed at 220 °C for 60 minutes following the T6 heat treatment and later re-aged at temperatures between 100 °C and 140 °C for 24 hours and at 120 °C for various durations in the range of 15–35 hours. The effects of temperature and duration of re-aging on hardness and the fatigue behaviors of RRA tempered 7075 aluminum alloys were investigated. The results show that temperature and duration of re-aging have an influence on both hardness and fatigue resistances. An increment of the hardness values depends on increasing of re-aging temperature and times until 120 °C and 24 hours and reaches to the maximum value. However, those values decrease with higher re-aging temperatures and longer duration than 120 °C and 24 hours, respectively. On the other hand, in the fatigue tests, the highest fatigue resistance was observed for the sample re-aged at 120 °C for 24 hours, while the sample re-aged at 140 °C for 24 hours showed the longest fatigue life under lower fatigue stress.