Aluminum 7178
AA 7178 · UNS A97178 · EN AW-7178, AW 7178
7178 is a heat-treatable Al-Zn-Mg-Cu alloy with roughly 6.3–7.3% Zn, one of the highest-strength conventional 7000-series wrought alloys, normally supplied as Alclad sheet and plate and as extrusions (A97178, AlZn7MgCu).
7178 tempers and conditions
7178 is supplied in 8 conditions, soft to hard.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Soft annealed stock for severe forming or machining before solution heat treatment and aging. | 103 | 228 | 15 | 60 HB | 38 % IACS |
Overaged for exfoliation-corrosion resistance | Choose when exfoliation-corrosion resistance matters more than the last 5 % of strength. | 505 | 570 | 11 | 150 HB | 38 % IACS |
T76, stress relieved by stretching | Over-aged plate with low residual stress — for machined skins needing exfoliation resistance and dimensional stability. | 510 | 572 | 10 | 150 HB | 38 % IACS |
T6, heat treated by the user | 7178 re-solution-treated from O/F temper and artificially aged by the fabricator; strength essentially equals T6 with no stretch stress relief. | 530 | 600 | 10 | 160 HB | 31 % IACS |
T6, stress relieved by stretching | Standard plate temper — same peak strength as T6 but low residual stress for stable machining of thick parts. | 530 | 600 | 9 | 160 HB | 31 % IACS |
Solution heat treated and artificially aged | Peak-strength condition — pick it for maximum static and compressive strength in sheet, clad sheet and simple sections. | 538 | 607 | 10 | 160 HB | 31 % IACS |
Solution treated, stretched, aged; extrusion without straightening… | Extruded stringer/section temper with controlled stretch and no subsequent straightening. | 570 | 620 | 8 | 165 HB | 31 % IACS |
T6, stress relieved by stretching, minor straightening | Most common high-strength extrusion temper — straightness-corrected version of T6510. | 570 | 620 | 8 | 165 HB | 31 % IACS |
What is 7178?
7178 is a heat-treatable Al-Zn-Mg-Cu alloy with roughly 6.3–7.3% Zn, one of the highest-strength conventional 7000-series wrought alloys, normally supplied as Alclad sheet and plate and as extrusions (A97178, AlZn7MgCu). It was developed for compression-loaded aircraft structure such as upper wing skins and stringers, where T6 tensile strength can exceed 600 MPa. Fracture toughness, resistance to stress-corrosion cracking and formability are poor, and the alloy cannot be fusion welded. Most new designs specify 7075, 7150 or 7055 instead. 7178 has a density of 2.83 g/cm³ (0.102 lb/in³), heavier than 91% of aluminum grades. It melts at 477°C (891 °F). 7178 has a yield strength of 538 MPa (78 ksi) and a tensile strength of 607 MPa (88 ksi) — stronger than 97% of aluminum grades. Elongation at break is 10% and the elastic modulus is 71.7 GPa (10.4 Msi).
What is 7178 used for?
- Aircraft upper wing skins
- Wing stringers
- Compression-loaded airframe panels
- Extruded stiffeners and spar caps
- Alclad aerospace sheet components
- Legacy airframe replacement parts
Advantages
- High strength — 538 MPa (78 ksi), better than 97% of aluminum grades
- Easy to machine — 72/100, better than 80% of aluminum grades
Limitations
- Difficult to weld — 12/100, worse than 98% of aluminum grades
- Needs corrosion protection — 32/100, worse than 94% of aluminum grades
- Limited service temperature — 120°C (248 °F), worse than 79% of aluminum grades
7178 properties
Typical room-temperature values; bars are the position among aluminum grades.
Physical3
7178 has a density of 2.83 g/cm³ (0.102 lb/in³), heavier than 91% of aluminum grades. It melts at 477°C (891 °F).
Mechanical13
7178 has a yield strength of 538 MPa (78 ksi) and a tensile strength of 607 MPa (88 ksi) — stronger than 97% of aluminum grades. Elongation at break is 10% and the elastic modulus is 71.7 GPa (10.4 Msi).
Thermal6
7178 is rated for continuous service to 120°C (248 °F). It conducts heat at 125 W/m·K (72.2 BTU/hr·ft·°F), worse than 72% of aluminum grades. Thermal expansion is 23.4 µm/m·K (13 µin/in·°F).
Electrical3
7178 conducts electricity at 31 % IACS, worse than 68% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is poor (32/100), worse than 94% of aluminum grades.
Sustainability4
Producing a kilogram of 7178 takes about 205 MJ of energy and emits 12.5 kg of CO₂ — more than 76% of aluminum grades. Typical recycled content is 15%.
Manufacturability7
7178's machinability is very good (72/100, better than 80% of aluminum grades); weldability not recommended (12/100); formability poor (20/100).
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. 7178 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 7178
Is 7178 easy to machine?
Machines well in T6/T76 with sharp carbide, high speed and flood coolant; relieve stresses (T651/T7651) before heavy pocket milling to control distortion.
Can 7178 be welded?
Not fusion weldable — hot cracking and severe HAZ SCC; join by riveting, bolting or adhesive bonding (friction-stir only with qualified procedures).
Can 7178 be formed, bent or molded?
Form in O or freshly quenched W temper and age afterwards; T6 sheet tolerates only large-radius bends and is prone to cracking.
Manufacturability
The process limits FabDigit applies to 7178. Every 7178 part is priced by an engineer; design inside these and the quote comes back without a redesign loop.
CNC machining
| Machinability | Excellent72 / 100 |
|---|---|
| ISO material group | N.1 |
| Cutting speed (rough / finish) | 350 / 420 m/min |
| Minimum wall | 0.5 mm |
| Minimum internal radius | 1 mm |
| Drill depth limit | 8× diameter |
| Best surface (machined / polished) | Ra 0.8 / — |
| Hardenable after machining | No |
Sheet metal
| Formability | Not Recommend20 / 100 |
|---|---|
| Weldability | Not Recommend12 / 100 |
7178 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 |
|---|---|---|
| Si | ≤ 0.4 | |
| Fe | ≤ 0.5 | |
| Cu | 1.6 – 2.4 | 2 |
| Mn | ≤ 0.3 | |
| Mg | 2.4 – 3.1 | 2.7 |
| Cr | 0.18 – 0.28 | 0.23 |
| Zn | 6.3 – 7.3 | 6.8 |
| Ti | ≤ 0.2 | |
| Others (each)each | ≤ 0.05 | |
| Others (total)total | ≤ 0.15 | |
| Al | balance |
What surface finishes work on 7178?
Clad or anodize (chromic/sulfuric) plus chromate conversion and primer for corrosion protection; avoid sustained short-transverse tensile stress and use T76 tempers in exfoliation-prone areas.
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).
Passivation
Conversion Coating
PVD Coating
Equivalent designations
Standards and trade names that resolve to Aluminum 7178 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- A97178
- Aluminum Association
- AA7178
- EN / DIN / Werkstoff-Nr.
- AW-7178AW 7178AlZn7MgCu
How much does 7178 cost?
7178 is a premium-cost aluminum ($$$), cheaper than about 58% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
7178 — frequently asked
What is 7178 used for?
7178 is typically used for aircraft upper wing skins, wing stringers, compression-loaded airframe panels, extruded stiffeners and spar caps, alclad aerospace sheet components and legacy airframe replacement parts. In short: compression aerospace alloy.
What is the yield strength of 7178?
7178 has a typical yield strength of 538 MPa (78 ksi) and a tensile strength of 607 MPa (88 ksi) — stronger than 97% of aluminum grades. Strength varies by condition: see the 8 listed tempers.
Is 7178 easy to machine?
Yes — machinability is rated very good (72/100, better than 80% of aluminum grades). Machines well in T6/T76 with sharp carbide, high speed and flood coolant; relieve stresses (T651/T7651) before heavy pocket milling to control distortion.
Can 7178 be welded?
Not readily — weldability is rated not recommended (12/100). Not fusion weldable — hot cracking and severe HAZ SCC; join by riveting, bolting or adhesive bonding (friction-stir only with qualified procedures).
What surface finishes work on 7178?
Clad or anodize (chromic/sulfuric) plus chromate conversion and primer for corrosion protection; avoid sustained short-transverse tensile stress and use T76 tempers in exfoliation-prone areas.
Can 7178 be formed, bent or molded?
Form in O or freshly quenched W temper and age afterwards; T6 sheet tolerates only large-radius bends and is prone to cracking.
What is the maximum service temperature of 7178?
7178 is rated for continuous use to about 120°C (248 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 7178 cost?
7178 is a premium-cost aluminum ($$$), cheaper than about 58% 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.
Can FabDigit make parts in 7178?
Yes — 7178 is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- International Alloy Designations and Chemical Composition Limits for Wrought Aluminum (Teal Sheets) — The Aluminum Association (2018)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- MMPDS-17 Metallic Materials Properties Development and Standardization — Battelle/FAA (2022)
- ASTM B209 / B221 — Aluminum Sheet, Plate and Extruded Products — ASTM International (2021)
- ASM Handbook Vol. 13B — Corrosion: Materials — ASM International (2005)
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.