1. Heat treatment process and core differences
7075-T6
Solution heat treatment + artificial aging (T6 state), strengthening MgZn₂ phase precipitation
Aging temperature: 120-130℃, aging time: 24 hours
7075-T73
Dual-stage aging process (T7-type treatment): high temperature aging (170-180℃) and then low temperature aging (120℃)
Reducing residual stress through over-aging treatment, sacrificing part of strength in exchange for improved corrosion resistance
2. Comparison of mechanical properties
Parameters 7075-T6 7075-T73
Tensile strength 570-600 MPa 480-520 MPa
Yield strength 505-540 MPa 430-460 MPa
Elongation 8-12% 10-15%
Hardness (HB) 150-160 135-145
3. Corrosion resistance
7075-T6:
Tendency to produce stress corrosion cracks, suitable for low corrosion environment
Salt spray test: 500-1000h (ASTM B117 standard)
7075-T73:
Stress corrosion resistance increased by more than 200%, suitable for marine/chemical environment
Salt spray test: 1500-2000h
4. Processing and welding characteristics
Machinability
T6 has higher hardness, and the tool wear rate is about 30% higher than T73
T73 has lower residual stress, and the precision machining deformation is reduced by 40%
Welding performance
T6 welding is prone to cracks, and 5356 welding wire is required
T73 can maintain more than 90% of the base material strength after welding
5. Typical application scenarios
Model Applicable field Representative use
7075-T6 High dynamic load structural parts Aircraft wing beams, missile racks, robot joints
7075-T73 Load-bearing parts in corrosive environments Ship decks, offshore drilling platform brackets, chemical reactors
6. Selection recommendations
Scenarios where T6 is preferred:
Ultimate strength (＞500MPa) and no long-term corrosion risk are required
Mechanical parts with short-term static loads as the main load
Scenarios where T73 is preferred:
Outdoor environments with large temperature/humidity fluctuations (such as tropical coastal areas)
Long-term service equipment that needs to withstand alternating stress or dynamic loads
Additional notes:
The chemical composition of the two is the same (Zn 5.1-6.1%, Mg 2.1-2.9%, Cu 1.2-2.0%), and the difference is entirely due to the heat treatment process. T73 sacrifices 10-15% strength in exchange for more than 3 times the corrosion resistance life, which is a typical example of material reliability design
