Abstract
Aluminum alloys of the 7xxx series (AA7075) are preferred in the aerospace and automotive industries due to their low densities, high strength, good corrosion resistance properties. Additionally, these alloys show the most effective aging properties among aluminum alloys. For this reason, it is very important to determine the most appropriate aging parameters for microstructural development. Literature review reveals that the effect of pre-strain on springback has not been studied yet. In this study, the effects of aging temperature, time, and pre-strain on mechanical properties are investigated for AA7075. Precipitates present in solid solutions of AA7075 and their effects are examined. Results reveal that MgZn2 precipitation is not observed at aging temperatures of 120 and 160 oC. After the formation of MgZn2 precipitates, microstructure becomes softer when aging continues at a higher temperature or longer period of time. It is clearly seen that pre-strain causes Portevin-Le Chatelier (PLC) effect after aging at 120 and 160 oC for aging times of 30 and 90 minutes.
Highlights
Aluminum alloys have specific characteristics depending on their chemical composition
86.4% is the highest difference on ultimate tensile strengths and seen at 120 °C, 2880 min
Pre-strain leads yield strength to decrease for all aging conditions
Summary
Aluminum alloys have specific characteristics depending on their chemical composition. AA 7075 alloys consists of Zn, Mg and Cu elements in addition to main Al matrix. They change microstructure and give specific features effecting manufacturing processes to be applied on. Aluminum alloys of the 7XXX series (AA7XXX) have been widely used in the aerospace industry due to their low densitiles, high strength, fracture toughness, and resistance to stress corrosion cracking 1-3. Phases in these alloys’ microstructures are key factors affecting their performance. Η(MgZn2), T (Al2CuMg), and S (Al2CuMg) phases are observed as secondary phases in 7XXX series of Al-Zn-Mg-Cu alloy 4-8
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