Aluminum 7175-T66
Precip hard
AA 7175 · EN AW-7175, AW 7175
T66 = t6 with improved mechanical properties
Highest-strength registered temper for 7175 die forgings when maximum static strength is needed.
Values for the T66 condition
Other 7175 tempers and conditions
7175 is listed in 13 conditions; see the grade overview at 7175.
Compare all 13 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Softest condition, used only for intermediate forming/machining before solution treatment. | 105 | 230 | 17 | 60 HB | 45 % IACS |
T73, stress relieved by stretching | Low-residual-stress overaged plate/bar for thick machined aerospace fittings. | 440 | 510 | 12 | 138 HB | 40 % IACS |
Overaged, stress relieved by cold compression | Large forgings that must be heavily machined — compression stress relief keeps parts dimensionally stable. | 440 | 510 | 10 | 142 HB | 39 % IACS |
Extrusion: overaged, stretched, minor straightening permitted | Overaged extruded shapes/bar where SCC resistance and straightness are both required. | 450 | 515 | 10 | 140 HB | 40 % IACS |
Solution treated, stress relieved by stretching/compression, overaged | Default aerospace supply condition: overaged for SCC resistance with residual stress removed for dimensionally stable machining. | 455 | 524 | 11 | 140 HB | 40 % IACS |
Overaged (T74) and stress relieved by cold restriking in the finish die | High-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 | 525 | 11 | 135 HB | 40 % IACS |
Solution heat treated and overaged for stress-corrosion resistance | Choose when short-transverse SCC resistance and toughness outrank peak strength. | 455 | 525 | 12 | 140 HB | 40 % IACS |
Overaged between T73 and T76 | The workhorse 7175 forging temper: near-T6 strength with T73-level SCC and toughness performance. | 455 | 524 | 11 | 145 HB | 39 % IACS |
Extrusion: T74 overaged, stretched, straightened | Extruded stringers/spar caps needing higher strength than T73511 with good SCC behaviour. | 490 | 545 | 10 | 148 HB | 38 % IACS |
Extrusion: overaged for exfoliation resistance, stretched | Intermediate overage giving good exfoliation resistance with strength above T73 tempers. | 490 | 545 | 10 | 148 HB | 38 % IACS |
T6, stress relieved by stretching | Peak-strength plate with low residual stress for stable machining of thick parts. | 515 | 585 | 11 | 150 HB | 33 % IACS |
Solution heat treated and artificially aged | Maximum strength condition for forgings/extrusions where SCC exposure is low. | 525 | 595 | 11 | 150 HB | 33 % IACS |
T66This page T6 with improved mechanical properties | Highest-strength registered temper for 7175 die forgings when maximum static strength is needed. | 560 | 620 | 9 | 160 HB | 32 % IACS |
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 — 80/100, better than 92% of aluminum grades
Limitations
- Difficult to weld — 10/100, worse than 99% 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; 22 are specific to this condition. Other listed values are 7175 reference data and may not represent this condition. Bars are the position among aluminum grades.
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 130 W/m·K (75.1 BTU/hr·ft·°F), worse than 65% 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 76% of aluminum grades. Typical recycled content is 8%.
Manufacturability7
7175-T66's machinability is very good (80/100, better than 92% of aluminum grades); weldability not recommended (10/100); formability poor (18/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
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 (80/100, better than 92% 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 (10/100). 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; 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)
- 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.