Aluminum 7A85
GB 7A85
7A85 is a newer-generation high-strength, high-toughness Al-Zn-Mg-Cu alloy in the GB/T 7000-series family, developed for thick-section aircraft structure and comparable to 7085 in role.
Reference datasheet — 7A85 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the T7451 condition
7A85 tempers and conditions
7A85 is supplied in 8 conditions, soft to hard. T7451 is the default FabDigit quotes; the values on this page are for it.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Softest condition, supplied for deep forming or machining of blanks before solution treatment. | 115 | 240 | 16 | 65 HB | 45 % IACS |
As fabricated | Mill product before heat treatment; properties not guaranteed, used as feedstock for forging or further heat treat. | 180 | 300 | 12 | 85 HB | 44 % IACS |
T73, stress relieved by stretching | Maximum SCC immunity for highly stressed thick sections, at the cost of ~8–10 % strength versus T7451. | 425 | 480 | 11 | 145 HB | 42 % IACS |
Solution treated, stress relieved by compression, over-aged | Standard temper for large 7A85 die forgings and hand forgings where stretching is impossible. | 455 | 500 | 9 | 152 HB | 40 % IACS |
T7451Default T74, stress relieved by stretching | Standard thick-plate aerospace temper: best balance of strength, through-thickness toughness and SCC resistance. | 470 | 510 | 10 | 155 HB | 40 % IACS |
T76, stress relieved by stretching | Slightly less over-aged than T74 — higher strength with good exfoliation resistance, typical for medium-thickness plate and skins. | 490 | 530 | 9 | 162 HB | 38 % IACS |
Extruded, solution treated, stretched, over-aged to T76 | Extruded stringers and profiles needing exfoliation resistance with near-peak strength. | 500 | 540 | 9 | 165 HB | 38 % IACS |
T6, stress relieved by stretching | Peak-strength plate temper — pick when maximum static strength matters more than SCC/exfoliation resistance. | 520 | 560 | 8 | 175 HB | 32 % IACS |
What is 7A85?
7A85 is a newer-generation high-strength, high-toughness Al-Zn-Mg-Cu alloy in the GB/T 7000-series family, developed for thick-section aircraft structure and comparable to 7085 in role. It combines 470 MPa yield, 510 MPa tensile, 10 % elongation and 155 HB with low quench sensitivity, so heavy plate and die forgings hold properties through the thickness; conductivity is 150 W/m·K and 40 % IACS. Corrosion resistance in over-aged T74/T76 tempers is better than 7A04/7B04 (score 48), but the alloy is not fusion weldable and service is limited to about 120 °C. 7B04 is the alternative where thin plate or extrusions are required. 7A85 has a density of 2.85 g/cm³ (0.103 lb/in³), heavier than 96% of aluminum grades. It melts at 476°C (889 °F). 7A85 has a yield strength of 470 MPa (68.2 ksi) and a tensile strength of 510 MPa (74 ksi) — stronger than 93% of aluminum grades. Elongation at break is 10% and the elastic modulus is 71 GPa (10.3 Msi).
What is 7A85 used for?
- aircraft bulkheads
- thick plate structural forgings
- high-toughness aerospace parts
Advantages
- Tough — resists crack growth — 40 MPa·√m (36.4 ksi·√in), better than 98% of aluminum grades
- High strength — 470 MPa (68.2 ksi), better than 93% of aluminum grades
- Easy to machine — 72/100, better than 80% of aluminum grades
Limitations
- Difficult to weld — 20/100, worse than 89% of aluminum grades
- Limited service temperature — 120°C (248 °F), worse than 79% of aluminum grades
7A85 properties
Typical room-temperature values for 7A85-T7451; bars are the position among aluminum grades.
Physical3
7A85 has a density of 2.85 g/cm³ (0.103 lb/in³), heavier than 96% of aluminum grades. It melts at 476°C (889 °F).
Mechanical14
7A85 has a yield strength of 470 MPa (68.2 ksi) and a tensile strength of 510 MPa (74 ksi) — stronger than 93% of aluminum grades. Elongation at break is 10% and the elastic modulus is 71 GPa (10.3 Msi).
Thermal6
7A85 is rated for continuous service to 120°C (248 °F). It conducts heat at 150 W/m·K (86.7 BTU/hr·ft·°F), better than 58% of aluminum grades. Thermal expansion is 23.6 µm/m·K (13.1 µin/in·°F).
Electrical3
7A85 conducts electricity at 40 % IACS, better than 72% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (48/100), worse than 58% of aluminum grades.
Sustainability4
Producing a kilogram of 7A85 takes about 210 MJ of energy and emits 13 kg of CO₂ — more than 88% of aluminum grades. Typical recycled content is 5%.
Manufacturability8
7A85's machinability is very good (72/100, better than 80% of aluminum grades); weldability poor (20/100); formability poor (25/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the aluminum family
Yield strength against density for every aluminum grade FabDigit runs. 7A85 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 7A85
Is 7A85 easy to machine?
Machines cleanly in T7x with sharp polished-flute carbide tools, high speed and flood coolant; watch residual-stress distortion when hogging thick plate — rough, stress-relieve/rest, then finish.
Can 7A85 be welded?
Not recommended for fusion welding (hot cracking, severe HAZ softening and SCC); join by fasteners or friction stir welding with post-weld aging where qualified.
Can 7A85 be formed, bent or molded?
Form in O or freshly solution-treated W temper; T7x plate is essentially limited to gentle bends with large radii, so most parts are machined from plate or die-forged.
7A85 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 |
|---|---|---|
| Znprincipal strengthening addition | 7 – 8 | 7.5 |
| Mg | 1.2 – 1.8 | 1.5 |
| Cuimproves SCC resistance in over-aged tempers | 1.3 – 2 | 1.6 |
| ZrAl3Zr dispersoids; replaces Cr for low quench sensitivity | 0.08 – 0.15 | 0.11 |
| Feheld low for fracture toughness | ≤ 0.08 | 0.05 |
| Si | ≤ 0.06 | 0.04 |
| Mn | ≤ 0.04 | |
| Cr | ≤ 0.04 | |
| Ti | ≤ 0.06 | |
| other, each | ≤ 0.05 | |
| other, total | ≤ 0.15 | |
| Al | balance |
What surface finishes work on 7A85?
Chromic/sulfuric or hard anodize plus chromate-free conversion coat and primer is standard; expect grey anodic film, avoid bright decorative finishes; shot peening improves SCC and fatigue life.
Surface treatments FabDigit runs on aluminum parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
How much does 7A85 cost?
7A85 is a high-cost aluminum ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
7A85 — frequently asked
What is 7A85 used for?
7A85 is typically used for aircraft bulkheads, thick plate structural forgings and high-toughness aerospace parts. In short: thick-section 7000-series grade; low quench sensitivity; high toughness at 470 MPa.
What is the yield strength of 7A85?
7A85 has a typical yield strength of 470 MPa (68.2 ksi) and a tensile strength of 510 MPa (74 ksi) — stronger than 93% of aluminum grades. Strength varies by condition: see the 8 listed tempers.
Is 7A85 easy to machine?
Yes — machinability is rated very good (72/100, better than 80% of aluminum grades). Machines cleanly in T7x with sharp polished-flute carbide tools, high speed and flood coolant; watch residual-stress distortion when hogging thick plate — rough, stress-relieve/rest, then finish.
Can 7A85 be welded?
Not readily — weldability is rated poor (20/100). Not recommended for fusion welding (hot cracking, severe HAZ softening and SCC); join by fasteners or friction stir welding with post-weld aging where qualified.
What surface finishes work on 7A85?
Chromic/sulfuric or hard anodize plus chromate-free conversion coat and primer is standard; expect grey anodic film, avoid bright decorative finishes; shot peening improves SCC and fatigue life.
Can 7A85 be formed, bent or molded?
Form in O or freshly solution-treated W temper; T7x plate is essentially limited to gentle bends with large radii, so most parts are machined from plate or die-forged.
What is the maximum service temperature of 7A85?
7A85 is rated for continuous use to about 120°C (248 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 7A85-T7451 and 7A85-O?
T7451 is the default condition — standard thick-plate aerospace temper: best balance of strength, through-thickness toughness and SCC resistance. O: softest condition, supplied for deep forming or machining of blanks before solution treatment. Yield strength is 470 MPa in T7451 versus 115 MPa in O.
How much does 7A85 cost?
7A85 is a high-cost aluminum ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- GB/T 3190 Wrought aluminium and aluminium alloys — Chemical composition — SAC (2020)
- GB/T 3880 / GB/T 3191 aluminium plate and extrusion product standards — SAC (2021)
- Aluminum Association Teal Sheets — Registration Record of Alloy Designations (7085 reference) — The Aluminum Association (2018)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- MMPDS-17 Metallic Materials Properties Development and Standardization — FAA/Battelle (2022)
- Thick aerospace plate 7085/7A85-T7451 datasheets — Arconic / Southwest Aluminium (2022)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.