Aluminum 7A04-T73
Temper
GB 7A04
T73 = solution heat treated and overaged for stress-corrosion resistance
Pick when stress-corrosion cracking or exfoliation risk (thick sections, sustained tension, marine/humid service) outweighs the ~8 % strength loss.
Values for the T73 condition
Other 7A04 tempers and conditions
7A04 is listed in 9 conditions; see the grade overview at 7A04.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Softest state for deep forming, bending or straightening before re-heat-treatment. | 110 | 235 | 16 | 60 HB | 45 % IACS |
As fabricated | Mill state of forging stock and hot-rolled slabs, bought for subsequent forging plus full heat treatment. | 200 | 320 | 12 | 90 HB | 40 % IACS |
Solution heat treated and naturally aged | Intermediate strength with better formability than T6; used when parts are formed after quenching and later artificially aged. | 300 | 470 | 13 | 120 HB | 32 % IACS |
T73, stress relieved by stretching | Thick-plate over-aged temper for machined aerospace fittings needing both low residual stress and SCC resistance. | 420 | 490 | 9 | 132 HB | 40 % IACS |
T73This page Solution heat treated and overaged for stress-corrosion resistance | Pick when stress-corrosion cracking or exfoliation risk (thick sections, sustained tension, marine/humid service) outweighs the ~8 % strength loss. | 430 | 500 | 10 | 135 HB | 40 % IACS |
Overaged for exfoliation-corrosion resistance | Compromise temper: most of T6 strength with much better exfoliation resistance in thin plate and extrusions. | 450 | 520 | 9 | 140 HB | 38 % IACS |
T6, heat treated by the user | Used when parts are formed in the O/F state and then given a full T6 treatment by the fabricator. | 460 | 530 | 8 | 145 HB | 33 % IACS |
T6, stress relieved by stretching | Thick plate temper of choice when large amounts of metal are machined away and distortion must be minimized. | 470 | 540 | 8 | 148 HB | 33 % IACS |
T6Default Solution heat treated and artificially aged | Standard peak-strength condition for machined structural parts, extrusions and forgings; default stock temper. | 475 | 545 | 8 | 150 HB | 33 % IACS |
What is 7A04-T73?
7A04-T73 is 7A04 in the T73 temper — pick when stress-corrosion cracking or exfoliation risk (thick sections, sustained tension, marine/humid service) outweighs the ~8 % strength loss. 7A04-T73 has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 500 MPa (72.5 ksi) — stronger than 90% of aluminum grades. Elongation at break is 10% and the elastic modulus is 71 GPa (10.3 Msi). 7A04-T73 has a density of 2.85 g/cm³ (0.103 lb/in³), heavier than 96% of aluminum grades. It melts at 477°C (891 °F). T6 is the default condition FabDigit quotes; T73 is available on request or by drawing note.
Advantages
- High strength — 430 MPa (62.4 ksi), better than 90% of aluminum grades
- Tough — resists crack growth — 32 MPa·√m (29.1 ksi·√in), better than 83% of aluminum grades
Limitations
- High embodied carbon — 14 kg CO₂/kg, worse than 95% of aluminum grades
- Difficult to weld — 20/100, worse than 89% of aluminum grades
7A04-T73 properties
Typical room-temperature values for 7A04-T73; 12 are specific to this condition. Other listed values are 7A04 reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
7A04-T73 has a density of 2.85 g/cm³ (0.103 lb/in³), heavier than 96% of aluminum grades. It melts at 477°C (891 °F).
Mechanical14
7A04-T73 has a yield strength of 430 MPa (62.4 ksi) and a tensile strength of 500 MPa (72.5 ksi) — stronger than 90% of aluminum grades. Elongation at break is 10% and the elastic modulus is 71 GPa (10.3 Msi).
Thermal6
7A04-T73 is rated for continuous service to 150°C (302 °F). It conducts heat at 155 W/m·K (89.6 BTU/hr·ft·°F), better than 71% of aluminum grades. Thermal expansion is 23.4 µm/m·K (13 µin/in·°F).
Electrical3
7A04-T73 conducts electricity at 40 % IACS, better than 72% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (50/100), worse than 56% of aluminum grades.
Sustainability4
Producing a kilogram of 7A04-T73 takes about 200 MJ of energy and emits 14 kg of CO₂ — less than 60% of aluminum grades. Typical recycled content is 10%.
Manufacturability6
7A04-T73's machinability is very good (70/100, better than 72% of aluminum grades); weldability poor (20/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 7A04-T73
Is 7A04 easy to machine?
Machines very freely in T6/T73 with sharp polished-flute carbide tools, high speeds and flood coolant/MQL; watch residual-stress distortion on thick plate — use T651/T7351 and symmetric roughing passes.
Can 7A04 be welded?
Not suitable for fusion welding (hot cracking, severe HAZ strength loss); join by riveting, bolting or adhesive, or use friction-stir/resistance spot welding with post-weld property allowance.
Can 7A04 be formed, bent or molded?
Form in O or T4 (or hot-form 200–350 °C) with generous bend radii; T6 material is prone to cracking, and forgings need controlled 400–460 °C forging plus solution quench.
What surface finishes work on 7A04?
Anodize (sulfuric, chromic or hard Type III), chromate/trivalent conversion coat plus epoxy primer for aerospace; avoid strong alkaline cleaners and give shot-peening on fatigue-critical surfaces.
7A04 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Zn | 5 – 7 | 6 |
| Mg | 1.8 – 2.8 | 2.3 |
| Cu | 1.4 – 2 | 1.7 |
| Mn | 0.2 – 0.6 | 0.4 |
| Cr | 0.1 – 0.25 | 0.17 |
| Feimpurity limit | ≤ 0.5 | — |
| Siimpurity limit | ≤ 0.5 | — |
| Tigrain refiner / impurity | ≤ 0.1 | — |
| Niimpurity limit | ≤ 0.1 | — |
| others (each)total 0.10 max | ≤ 0.05 | — |
| Al | balance | — |
7A04-T73 — frequently asked
What is 7A04-T73 used for?
7A04-T73 is typically used for aircraft structural forgings, high-strength machined parts and landing gear components. In short: 7075-class strength level; high-strength forging grade; not fusion weldable.
What is the yield strength of 7A04-T73?
7A04-T73 has a typical yield strength of 430 MPa (62.4 ksi) and a tensile strength of 500 MPa (72.5 ksi) — stronger than 90% of aluminum grades. Strength varies by condition: see the 9 listed tempers.
Is 7A04-T73 easy to machine?
Yes — machinability is rated very good (70/100, better than 72% of aluminum grades). Machines very freely in T6/T73 with sharp polished-flute carbide tools, high speeds and flood coolant/MQL; watch residual-stress distortion on thick plate — use T651/T7351 and symmetric roughing passes.
Can 7A04-T73 be welded?
Not readily — weldability is rated poor (20/100). Not suitable for fusion welding (hot cracking, severe HAZ strength loss); join by riveting, bolting or adhesive, or use friction-stir/resistance spot welding with post-weld property allowance.
What surface finishes work on 7A04-T73?
Anodize (sulfuric, chromic or hard Type III), chromate/trivalent conversion coat plus epoxy primer for aerospace; avoid strong alkaline cleaners and give shot-peening on fatigue-critical surfaces.
Can 7A04-T73 be formed, bent or molded?
Form in O or T4 (or hot-form 200–350 °C) with generous bend radii; T6 material is prone to cracking, and forgings need controlled 400–460 °C forging plus solution quench.
What is the maximum service temperature of 7A04-T73?
7A04-T73 is rated for continuous use to about 150°C (302 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 7A04-T6 and 7A04-O?
T6 is the default condition — standard peak-strength condition for machined structural parts, extrusions and forgings; default stock temper. O: softest state for deep forming, bending or straightening before re-heat-treatment. Yield strength is 475 MPa in T6 versus 110 MPa in O.
Sources
- ASM Handbook Vol. 2 — Properties of Nonferrous Alloys (7075) — ASM International (1990)
- MMPDS-17 Metallic Materials Properties Development and Standardization — Battelle/FAA (2022)
- Aluminum Association Teal Sheets — registered alloy/temper data — The Aluminum Association (2018)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.