7075 aluminum block is an aluminum-zinc-magnesium-copper high-strength deformed aluminum alloy that can be heat-treated and strengthened. It is the elder of super-duralumin. It is used to manufacture various structural parts, especially aerospace vehicle structural parts. The most widely used high-strength aluminum alloy today, as large as the front fuselage long truss of the C919 large aircraft, passenger observation window frame forgings, middle fuselage sheet bending and long truss, keel beam webs, floor turning beams, middle and rear fuselage length Truss, passenger observation window frame forgings, cargo door frame, front pressure frame edge of the nose, cabin door frame, etc.; as small as a mobile phone shell. It has a variety of heat treatment states: T6, T73, T76, T77. The T6 state material has the highest mechanical strength performance, but the fracture toughness is low, it is sensitive to stress corrosion, and its toughness decreases with the decrease of temperature. Therefore, the T6 state material is not suitable for manufacturing low-temperature structural parts and workpieces; T73 material has the lowest strength , But has quite high fracture toughness, good stress cracking resistance and spalling corrosion resistance; T76 material has higher strength than T73 material and higher stress corrosion cracking resistance than T6 material. The static strength performance of 7075 alloy is higher than that of 2024 and 2124 alloy, and the fatigue performance is equivalent to it. O state and W state materials have good room temperature molding properties.
7075 aluminum block can be resistance welded, and the long-term working temperature of the workpiece is ≤125℃. Incomplete annealing specifications for materials or workpieces 290℃~320℃, after holding for 2h~4h, air cooling out of the furnace; complete annealing specifications (390~430)℃/(0.5~1.5)h, with a cooling rate of not more than 30℃/h Cool to ≤200℃, then air-cool.
The solution treatment temperature of
7075 aluminum block is 460℃~490℃, and the treatment temperature of aluminum sheet should be close to the lower limit, and the number of repeated treatments should not be more than 2 times, so as to prevent alloy elements from diffusing through the aluminum clad layer and reducing the corrosion resistance of the material ; The heating temperature of the extruded material is 460℃~471℃. After heat preservation, quench in room temperature water or warm water or other suitable cooling medium, the transfer time should be less than 15s.
7075 aluminum block will generate a lot of internal stress after quenching. It must be stretched before aging treatment to reduce it to the allowable range. Therefore, this kind of stretching is called pre-stretching, and the pre-stretching amount is 1.5 %~3%, otherwise serious deformation will occur.
