Al-Zn-Mg-Cu alloy is an age-strengthening aluminum alloy, and its strengthening mechanism is to uniformly precipitate fine and dispersed strengthening phases from the supersaturated solid solution during the aging process.
The aging system of high-strength aluminum alloys has been continuously developed against the background of aviation demand, from the initial peak aging (T6) to two-stage aging (T7X) and three-stage aging precision heat treatment technology (T77).
The main purpose of T6 is to improve the static strength of the alloy. T7X is to make the grain boundary phase discontinuously precipitate on the basis of the over-aging principle, and to improve the stress corrosion resistance by reducing the strength. And T77 can meet the requirements of fracture toughness, corrosion resistance and fatigue resistance without sacrificing the strength of the alloy.
7150 aluminum plate with T77 temper is to meet the overall needs of aviation materials for high strength and high stress corrosion resistance. It is the iconic alloy of the fourth generation of high-strength, high-toughness and corrosion-resistant aluminum alloys and has been widely used in aircraft upper wing structures.
With the extension of the regression aging time, the corrosion resistance of 7150 aluminum plate continues to increase. With the extension of the regression time, the η'of the alloy will continue to re-dissolve, producing PFZ around the grain boundary. While the grain boundary phase continues to coarsen, the continuity of the grain boundary weakens, which also promotes the enhancement of corrosion resistance.
The final three-stage aging treatment of 7150 aluminum is 105℃/17h+190℃/30min+120℃/23h. Under this system, the alloy's tensile strength, yield strength and elongation are 608, 544MPa and 10.4% respectively. The exfoliation corrosion rating is EA, and the constant load test tensile strength and elongation loss are 4.9% and 5.0% respectively.
Original Source:https://www.aircraftaluminium.com/a/7150-aluminum-plates-processing-method.html
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