چكيده به لاتين
Aluminum alloys are greatly used in sheet metal forming processes because of their desirable mechanical properties and high strength to weight ratio. Aluminum alloys series 2000 and 6000 have very convenient properties and features. Specificly, AA6061 and AA2024 are more famous and have more applications in these series. Aging treatment can improve the strength of these alloys, while the formability could greatly be affected simultaneously. In this thesis, the effects of aging temperature and time have been investigated on mechanical properties, microstructure and formability of these two alloys. For alloy AA6061, the aging treatment is implemented in artificial condition (T6) at constant aging duration (4 hours) and at different temperatures (140, 160, 180 and 200°C). Also for alloy AA2024, aging treatment is performed in natural condition (T4) at room temperature with variable aging durations (0, 0.5, 1.5, 4 and 24 hours). The AA6061 results illustrate that from solution to peak-aging (180°C), the ultimate tensile strength (UTS) and micro-hardness are increased 76% and 64%, respectively. Then, at over-aging condition these properties are decreased slightly. Moreover the forming limit diagrams (FLDs-Nakazima test) demonstrate that the formability from solution to peak-aging decreases and then in over-aging condition increases slightly. The FLD0 from solution to peak-aging decreases by 62%. For alloy AA2024, the natural aging experiments are recorded for different aging durations (0, 0.5, 1.5, 4 and 24 hours). The results show that the hardness and UTS increased finally by 107% and 31% with more precipitates. By increasing the strength, the elongation is declined about 16% and FLDo about 49%. Also, microstructural investigations for alloy AA2024 is performed by scanning electron microscopy (SEM). The results illustrate that after 24 hours aging, the amount and scattering of the precipitates are increased which justifies the increasing of strength and hardness.
