Aluminum 7175 · precip hard
Aluminum 7175-T66
Properties of the T66 condition, compared with the other 7175 tempers.
Highest-strength registered temper for 7175 die forgings when maximum static strength is needed.
What is 7175-T66?
7175-T66 is 7175 in the T66 condition — highest-strength registered temper for 7175 die forgings when maximum static strength is needed. 7175-T66 has a yield strength of 560 MPa (81.2 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 98% of aluminum grades. Elongation at break is 9% and the elastic modulus is 71.7 GPa (10.4 Msi). 7175-T66 has a density of 2.8 g/cm³ (0.101 lb/in³), heavier than 81% of aluminum grades. It melts at 477°C (891 °F).
Advantages
- High strength — 560 MPa (81.2 ksi), better than 98% of aluminum grades
- Easy to machine — 78/100, better than 89% 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
7175-T66 properties
Typical room-temperature values for 7175-T66 — 9 properties are specific to this condition; the rest are grade-level values shared by every 7175 temper. Each bar shows where the value sits among the aluminum grades in FabDigit's library — further right is higher.
Physical3
7175-T66 has a density of 2.8 g/cm³ (0.101 lb/in³), heavier than 81% of aluminum grades. It melts at 477°C (891 °F).
Mechanical14
7175-T66 has a yield strength of 560 MPa (81.2 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 98% of aluminum grades. Elongation at break is 9% and the elastic modulus is 71.7 GPa (10.4 Msi).
Thermal6
7175-T66 is rated for continuous service to 120°C (248 °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
7175-T66 conducts electricity at 32 % IACS, worse than 63% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is poor (32/100), worse than 94% of aluminum grades.
Sustainability4
Producing a kilogram of 7175-T66 takes about 205 MJ of energy and emits 12.5 kg of CO₂ — more than 75% of aluminum grades. Typical recycled content is 8%.
Manufacturability7
7175-T66's machinability is very good (78/100, better than 89% of aluminum grades); weldability not recommended (12/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 7175 tempers and conditions
7175 is also supplied in 12 other conditions. The full side-by-side table is on the 7175 overview.
- T66Highest-strength registered temper for 7175 die forgings when maximum static strength is needed.560 MPa yield · 160 HB
- T6Maximum strength condition for forgings/extrusions where SCC exposure is low.525 MPa yield · 150 HB
- T651Peak-strength plate with low residual stress for stable machining of thick parts.515 MPa yield · 150 HB
- T73651Default aerospace supply condition: overaged for SCC resistance with residual stress removed for dimensionally stable machining.455 MPa yield · 140 HB
- T7454High-strength Al-Zn-Mg-Cu die-forging temper: T74 two-step overage giving near-T6 strength with good SCC and exfoliation resistance, residual stress removed by cold restrike in the finish die.455 MPa yield · 135 HB
- T73Choose when short-transverse SCC resistance and toughness outrank peak strength.455 MPa yield · 140 HB
- T74The workhorse 7175 forging temper: near-T6 strength with T73-level SCC and toughness performance.455 MPa yield · 145 HB
- T7351Low-residual-stress overaged plate/bar for thick machined aerospace fittings.440 MPa yield · 138 HB
- T7452Large forgings that must be heavily machined — compression stress relief keeps parts dimensionally stable.440 MPa yield · 142 HB
- OSoftest condition, used only for intermediate forming/machining before solution treatment.105 MPa yield · 60 HB
Working with 7175-T66
Is 7175 easy to machine?
Machines very well in T7x tempers with sharp polished carbide, high speed and flood coolant; expect long chips and use chip-breaking geometry.
Can 7175 be welded?
Not arc weldable for structure (hot-cracking, SCC in HAZ); join by riveting, bolting, adhesive bonding or friction stir welding with process qualification.
Can 7175 be formed, bent or molded?
Forge/hot work at ~380–440 °C; cold forming in T-tempers is very limited — form in O or W temper and re-heat-treat.
What surface finishes work on 7175?
Chromic/sulfuric anodize, Type III hardcoat, chemical conversion coating (Alodine) plus primer; avoid caustic etch overexposure on close-tolerance machined parts.
7175 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 | 5.1 – 6.1 | 5.6 |
| Mg | 2.1 – 2.9 | 2.5 |
| Cu | 1.2 – 2 | 1.6 |
| Crgrain-structure control | 0.18 – 0.28 | 0.23 |
| Ferestricted vs 7075 for toughness | ≤ 0.2 | 0.12 |
| Sirestricted vs 7075 | ≤ 0.15 | 0.08 |
| Mn | ≤ 0.1 | 0.03 |
| Ti | ≤ 0.1 | 0.03 |
| Others (each) | ≤ 0.05 | — |
| Others (total) | ≤ 0.15 | — |
| Al | balance | — |
7175-T66 — frequently asked
What is 7175-T66 used for?
7175-T66 is typically used for aircraft structural fittings, helicopter rotor hubs, fuselage frames and bulkheads, landing gear components, wing and spar forgings and highly loaded machined brackets. In short: premium aerospace forging.
What is the yield strength of 7175-T66?
7175-T66 has a typical yield strength of 560 MPa (81.2 ksi) and a tensile strength of 620 MPa (89.9 ksi) — stronger than 98% of aluminum grades. Strength varies by condition: see the 13 listed tempers.
Is 7175-T66 easy to machine?
Yes — machinability is rated very good (78/100, better than 89% of aluminum grades). Machines very well in T7x tempers with sharp polished carbide, high speed and flood coolant; expect long chips and use chip-breaking geometry.
Can 7175-T66 be welded?
Not readily — weldability is rated not recommended (12/100). Not arc weldable for structure (hot-cracking, SCC in HAZ); join by riveting, bolting, adhesive bonding or friction stir welding with process qualification.
What surface finishes work on 7175-T66?
Chromic/sulfuric anodize, Type III hardcoat, chemical conversion coating (Alodine) plus primer; avoid caustic etch overexposure on close-tolerance machined parts.
Can 7175-T66 be formed, bent or molded?
Forge/hot work at ~380–440 °C; cold forming in T-tempers is very limited — form in O or W temper and re-heat-treat.
What is the maximum service temperature of 7175-T66?
7175-T66 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.
Can FabDigit make parts in 7175-T66?
Yes — 7175-T66 is available for CNC machining and sheet metal with instant online pricing. 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)
- AMS 4149 — Aluminum Alloy 7175 Die Forgings and Rolled Rings, T74 — SAE International (2018)
- ASTM B247 — Aluminum-Alloy Die, Hand and Rolled Ring Forgings — ASTM International (2020)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- MMPDS — Metallic Materials Properties Development and Standardization — Battelle/FAA (2019)
- ASM Handbook Vol. 13B — Corrosion: Materials — ASM International (2005)
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.