, Shiraz University
Materials Engineering, Shiraz University
Aluminum 2024 and 7075 alloys which are widely used in aerospace and marine applications were chosen to investigate their strengthening mechanisms. Using differential thermal analysis (DIA), metallography and tension tests, the best solutionizing conditions were determined to be 500±5°C and 2 hours for 2024 and 480?±5°C and 1 hour for 7075 alloy. Aging was performed in the range of 100 to 200°C for various times. It was concluded that the maximum strength in 2024 alloy was developed at l80-190°C after 10 hours and in 7075 alloy at 120°C for 28 hours. In order to determine the strengthening mechanisms in these alloys qualitatively, the T8 treatment (cold work plus aging) was carried out. The results show an increase in the mechanical strength of 2024 alloy whereas the 7075 alloy was not affected appreciably by cold working. It can be concluded that the strengthening mechanism in the 2024 alloy is due to the stress field around the precipitates, whereas in the 7075 alloy it is due to chemical strengthening.