基于原位电阻法的 7A65 铝合金厚板双级时效工艺

With the increasing scarcity of traditional energy sources such as petroleum, the concept of sustainable development has prompted strict demands for energy-saving, economical, and environment-friendly industrial production. As the most important lightweight structural material, the requirements for aluminum alloys in modern industries are also increasing. In particular, 7xxx-series ultrahigh-strength aluminum alloy thick plates have been widely used in aerospace and other fields due to its advantages of lightweight and high specific strength. Currently, the problem of nonuniformity of microstructure and mechanical properties in the thickness direction of the thick plates is still prominent. Therefore, developing a new aging process to overcome the shortcomings of the low efficiency of traditional aging processes and difficult-to-control temperature field is urgently needed. Additionally, the research on aging heat treatment mainly focuses on the performance test and static microstructure characterization. Fewer research works have been carried out on the real-time detection of the transformation of the aging dissolution phase by in situ means. To optimize the two-stage aging process of a 7A65 aluminum alloy thick plate, this study systematically analyzed the aging precipitation behavior of the alloy by in situ electrical resistance analysis, formulated the two-stage aging process of the alloy, and explored the influence law of the aging process on the mechanical properties of the thick plate. The study also explored the strengthening and toughening mechanism of the plate through the microstructure observation and mechanical property test. The isothermal transition curve (i.e., time-temperature-transformation (TTT) curve) of the alloy shows that the “C curve”of η-phase dissolution is observed at 120-220 ^oC. According to the TTT curve, the optimal conditions for the two-stage aging process for the thick plate are determined to be as follows: heat at 121 ^oC for 6 h, and then at 152 ^oC for 19 h. After aging, the electrical conductivity of the plate is higher than 38%IACS, the yield strength is higher than 550 MPa, and the elongation reaches 9%.