Marine 7A33 aluminum alloy is a kind of Chinese Al-Zn-Mg-Cu heat-treated and reinforced corrosion-resistant high-strength deformed aluminum alloy. It has been listed in GB/T 3190-1996 "Chemical composition of deformed aluminum and aluminum alloy". It is the development of the 7033 alloy registered in the United States in 1986.

Marine 7A33 aluminum alloy has high seawater and marine atmospheric corrosion resistance, no intergranular corrosion, stress corrosion cracking and exfoliation corrosion sensitivity, strength comparable to 2A12 hard aluminum alloy, good fracture toughness, process plasticity and low Notch sensitivity, good weldability, suitable for spot welding, seam welding, friction stir welding, is a good material for the manufacture of helicopters, ships and ships used in seaplanes, amphibious aircraft, carrier aircraft, shipboard and coastal areas, can replace 2A12 alloy is used for the skin and structural parts of these aircraft, ship shells, etc.


Process performance of marine 7A33 aluminum alloy
Complete annealing: (390 ° C ~ 420 ° C) / h, and then with the cooling rate of ≤ 30 ° C / h with the furnace cooled to 200 ° C, then air cooled. Intermediate annealing: (320 ° C ~ 350 ° C) / (1h ~ 2h), followed by air cooling.
Solution annealing: (460 ° C ± 5 ° C) / (20 min ~ 40 min), quenching in water ≤ 40 ° C. The time for repeating the solution treatment is halved, and the number of times is ≤2 times.
Bipolar artificial aging: first stage (70 ° C ~ 90 ° C) / (10h ~ 20h); second level (150 ° C ± 5 ° C) / (10h ~ 20h). The time interval between solution treatment and human aging is not limited.
Physical and chemical properties
The melting temperature range of ship 7A33 aluminum alloy (606°C~643°C), the thermal conductivity of 100°C 109W/(m·°C), the specific heat capacity of -20J/(kg·°C) of 20°C~100°C, 20°C~ The coefficient of linear expansion at 100 ° C is 22.7 x 10-6 / ° C.
The density of the alloy was 2.78 g/cm3; the conductivity of the uncoated aluminum 7A33-T6 was 23.2 MS/m, and the resistivity was 44.7 nΩ·m;
Like other marine aluminum alloys, marine 7A33 aluminum alloy has excellent oxidation resistance, good corrosion resistance in various environments, and no intergranular corrosion, stress corrosion cracking and peeling corrosion tendency.
Organizational structure
The main strengthening phase of marine 7A33 aluminum alloy in solution treatment and artificial aging (T6) is η`, in the form of flakes, in addition to the dispersed phase E (Al12Cr2Mg3) containing Cr, the impurity phase is Al3Fe and Al-Fe- The Si compound has a precipitated η phase at the grain boundary.
Process performance
The marine 7A33 aluminum alloy has good rolling performance and forming process performance under hot and cold conditions. The plasticity index of the thin plate is better than that of the 2A12 alloy, and can be made into various seaplanes and marine structural components. The alloy has small deformation resistance and long incubation period in the newly quenched state, which is extremely advantageous for forming parts.
The alloy has good friction stir welding performance (FSW), spot welding and seam welding performance is also good, the tendency to form cracks is smaller than that of 2A12 alloy. The surface treatment process of marine 7A33 aluminum alloy is the same as that of hard aluminum, and the machinability and grinding performance are comparable to those of other alloys of the 7 series.
Marine 7A33 aluminum alloy has been widely used in seaplanes and amphibious aircraft manufactured in China.