Aluminum 7B04-T74
Temper
GB 7B04
T74 = overaged between T73 and T76
Compromise temper for forgings needing more strength than T73 with most of its SCC resistance.
Values for the T74 condition
Other 7B04 tempers and conditions
7B04 is listed in 10 conditions; see the grade overview at 7B04.
Compare all 10 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Pick for maximum formability during sheet forming or deep machining, then re-heat-treat to T6/T73. | 115 | 250 | 16 | 62 HB | 45 % IACS |
T73, stress relieved by stretching | Best combination of toughness, SCC immunity and machining stability for thick plate parts. | 400 | 470 | 11 | 133 HB | 40 % IACS |
Solution heat treated and overaged for stress-corrosion resistance | Pick for forgings and fittings exposed to humid/marine service where stress-corrosion cracking must be eliminated. | 405 | 480 | 11 | 135 HB | 40 % IACS |
T74This page Overaged between T73 and T76 | Compromise temper for forgings needing more strength than T73 with most of its SCC resistance. | 430 | 500 | 10 | 140 HB | 38 % IACS |
T74, stress relieved by stretching | Standard aerospace thick-plate temper for wing skins, spars and machined frames — high strength with good toughness and exfoliation resistance. | 440 | 510 | 10 | 143 HB | 38 % IACS |
Overaged for exfoliation-corrosion resistance | Choose for thin sheet/extrusions where exfoliation resistance matters but T73 strength loss is unacceptable. | 450 | 515 | 10 | 145 HB | 37 % IACS |
T76, stress relieved by stretching | Use for machined plate details needing exfoliation resistance and low residual stress. | 450 | 520 | 9 | 146 HB | 37 % IACS |
T6, heat treated by the user | Use when parts were formed/machined in O temper and then re-solution-treated and aged in-house. | 460 | 530 | 10 | 148 HB | 33 % IACS |
T6, stress relieved by stretching | Choose for peak-strength plate that will be heavily machined and must stay dimensionally stable. | 465 | 535 | 10 | 150 HB | 33 % IACS |
T6Default Solution heat treated and artificially aged | Default peak-strength condition for sheet, extrusions and forgings where static strength governs and SCC exposure is controlled. | 470 | 540 | 11 | 150 HB | 33 % IACS |
What is 7B04-T74?
7B04-T74 is 7B04 in the T74 temper — compromise temper for forgings needing more strength than T73 with most of its SCC resistance. 7B04-T74 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). 7B04-T74 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; T74 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
- Easy to machine — 72/100, better than 80% of aluminum grades
Limitations
- Difficult to weld — 18/100, worse than 94% of aluminum grades
7B04-T74 properties
Typical room-temperature values for 7B04-T74; 20 are specific to this condition. Other listed values are 7B04 reference data and may not represent this condition. Bars are the position among aluminum grades.
Physical3
7B04-T74 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).
Mechanical13
7B04-T74 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
7B04-T74 is rated for continuous service to 145°C (293 °F). It conducts heat at 148 W/m·K (85.5 BTU/hr·ft·°F), better than 56% of aluminum grades. Thermal expansion is 23.4 µm/m·K (13 µin/in·°F).
Electrical3
7B04-T74 conducts electricity at 38 % IACS, better than 61% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (50/100), worse than 56% of aluminum grades.
Sustainability4
Producing a kilogram of 7B04-T74 takes about 205 MJ of energy and emits 13 kg of CO₂ — more than 76% of aluminum grades. Typical recycled content is 5%.
Manufacturability7
7B04-T74's machinability is very good (72/100, better than 80% of aluminum grades); weldability poor (18/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 7B04-T74
Is 7B04 easy to machine?
Machines freely with sharp carbide tooling, high speed and generous coolant; over-aged T74xx/T73xx plate is preferred for thin-web parts because residual stress and distortion are much lower than in T6.
Can 7B04 be welded?
Not fusion-weldable for structural joints (hot cracking, severe HAZ property loss); join by riveting, bolting, adhesive bonding, resistance spot welding or friction stir welding.
Can 7B04 be formed, bent or molded?
Form in O or freshly quenched W condition; T6/T7 tempers tolerate only large-radius bending, and hot forging/extrusion is done around 380–450 °C followed by full solution treatment and ageing.
What surface finishes work on 7B04?
Chromic or sulfuric acid anodize plus chromate/chromate-free conversion coating and primer is standard aerospace practice; peak-aged T6 parts should be shot-peened or clad and kept out of sustained tensile short-transverse stress to avoid SCC.
7B04 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 – 6.5 | 5.7 |
| Mg | 1.8 – 2.8 | 2.3 |
| Cu | 1.4 – 2 | 1.7 |
| Mn | 0.2 – 0.6 | 0.35 |
| Cr | 0.1 – 0.25 | 0.17 |
| Feimpurity limit (lower than 7A04) | ≤ 0.25 | — |
| Siimpurity limit | ≤ 0.1 | — |
| Ti | ≤ 0.05 | — |
| Others (each)total ≤ 0.10 | ≤ 0.05 | — |
| Al | balance | — |
7B04-T74 — frequently asked
What is 7B04-T74 used for?
7B04-T74 is typically used for aircraft wing skins, high-strength structural extrusions and aerospace forgings. In short: 7150/7055-class aerospace plate; high strength with usable elongation; machined, not welded.
What is the yield strength of 7B04-T74?
7B04-T74 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 10 listed tempers.
Is 7B04-T74 easy to machine?
Yes — machinability is rated very good (72/100, better than 80% of aluminum grades). Machines freely with sharp carbide tooling, high speed and generous coolant; over-aged T74xx/T73xx plate is preferred for thin-web parts because residual stress and distortion are much lower than in T6.
Can 7B04-T74 be welded?
Not readily — weldability is rated poor (18/100). Not fusion-weldable for structural joints (hot cracking, severe HAZ property loss); join by riveting, bolting, adhesive bonding, resistance spot welding or friction stir welding.
What surface finishes work on 7B04-T74?
Chromic or sulfuric acid anodize plus chromate/chromate-free conversion coating and primer is standard aerospace practice; peak-aged T6 parts should be shot-peened or clad and kept out of sustained tensile short-transverse stress to avoid SCC.
Can 7B04-T74 be formed, bent or molded?
Form in O or freshly quenched W condition; T6/T7 tempers tolerate only large-radius bending, and hot forging/extrusion is done around 380–450 °C followed by full solution treatment and ageing.
What is the maximum service temperature of 7B04-T74?
7B04-T74 is rated for continuous use to about 145°C (293 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 7B04-T6 and 7B04-O?
T6 is the default condition — default peak-strength condition for sheet, extrusions and forgings where static strength governs and SCC exposure is controlled. O: pick for maximum formability during sheet forming or deep machining, then re-heat-treat to T6/T73. Yield strength is 470 MPa in T6 versus 115 MPa in O.
Sources
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- MMPDS typical property data for 7000-series aerospace plate (comparison basis) — Battelle/FAA (2023)
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.