Aluminum 7A77 · heat-treated state
Aluminum 7A77 Stress Relieved
Properties of the Stress Relieved condition, compared with the other 7A77 tempers.
Choose when distortion control during plate removal and machining matters more than peak strength; strength drops slightly as precipitates coarsen.
What is 7A77 Stress Relieved?
7A77 Stress Relieved is 7A77 heat treated to Stress Relieved — choose when distortion control during plate removal and machining matters more than peak strength; strength drops slightly as precipitates coarsen. 7A77 Stress Relieved has a yield strength of 270 MPa (39.2 ksi) and a tensile strength of 360 MPa (52.2 ksi) — stronger than 69% of aluminum grades. Elongation at break is 7% and the elastic modulus is 70 GPa (10.2 Msi). 7A77 Stress Relieved has a density of 2.81 g/cm³ (0.102 lb/in³), heavier than 86% of aluminum grades. It melts at 477°C (891 °F). As Printed is the default condition FabDigit quotes; Stress Relieved is available on request or by drawing note.
Limitations
- Limited service temperature — 100°C (212 °F), worse than 91% of aluminum grades
- Poor heat conductor — 120 W/m·K (69.3 BTU/hr·ft·°F), worse than 79% of aluminum grades
- Difficult to weld — 25/100, worse than 76% of aluminum grades
- Needs corrosion protection — 40/100, worse than 75% of aluminum grades
7A77 Stress Relieved properties
Typical room-temperature values for 7A77 Stress Relieved — 9 properties are specific to this condition; the rest are grade-level values shared by every 7A77 temper. Each bar shows where the value sits among the aluminum grades in FabDigit's library — further right is higher.
Physical3
7A77 Stress Relieved has a density of 2.81 g/cm³ (0.102 lb/in³), heavier than 86% of aluminum grades. It melts at 477°C (891 °F).
Mechanical14
7A77 Stress Relieved has a yield strength of 270 MPa (39.2 ksi) and a tensile strength of 360 MPa (52.2 ksi) — stronger than 69% of aluminum grades. Elongation at break is 7% and the elastic modulus is 70 GPa (10.2 Msi).
Thermal6
7A77 Stress Relieved is rated for continuous service to 100°C (212 °F). It conducts heat at 120 W/m·K (69.3 BTU/hr·ft·°F), worse than 79% of aluminum grades. Thermal expansion is 23.4 µm/m·K (13 µin/in·°F).
Electrical3
7A77 Stress Relieved conducts electricity at 30 % IACS, worse than 73% of aluminum grades.
Chemical & Environmental3
Corrosion resistance is fair (40/100), worse than 75% of aluminum grades.
Sustainability4
Producing a kilogram of 7A77 Stress Relieved takes about 215 MJ of energy and emits 13 kg of CO₂ — more than 92% of aluminum grades. Typical recycled content is 5%.
Manufacturability8
7A77 Stress Relieved's machinability is good (66/100, better than 66% of aluminum grades); weldability poor (25/100); formability poor (20/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other 7A77 tempers and conditions
7A77 is also supplied in 5 other conditions. The full side-by-side table is on the 7A77 overview.
- As PrintedDefaultBaseline condition straight off the LPBF machine; crack-free equiaxed structure but supersaturated and residually stressed — use only for form/fit or before heat treatment.310 MPa yield · 110 HB
- HIP+T6Best overall combination for flight-type hardware: densified by HIP then aged to peak strength, giving T6 strength with better ductility and fatigue scatter.485 MPa yield · 152 HB
- T6Standard delivery condition for structural AM parts — gives strength close to wrought 7075-T6; least resistant to stress-corrosion cracking.480 MPa yield · 150 HB
- T73Pick when the part sees sustained tensile stress in humid or marine service; roughly 10–15 % lower strength than T6 but far better SCC and exfoliation resistance.400 MPa yield · 135 HB
- Stress RelievedChoose when distortion control during plate removal and machining matters more than peak strength; strength drops slightly as precipitates coarsen.270 MPa yield · 100 HB
- HIPUse for fatigue- or leak-critical parts: HIP collapses gas/lack-of-fusion porosity and raises ductility, but the slow cool leaves the alloy soft until re-aged.250 MPa yield · 95 HB
Working with 7A77 Stress Relieved
Is 7A77 easy to machine?
Machines like 7075 — sharp uncoated carbide, high speed, generous coolant; expect springy thin walls and beware of subsurface porosity opening up on finish passes.
Can 7A77 be welded?
Fusion welding of 7xxx is still discouraged (hot cracking, HAZ softening); use mechanical joints, adhesive, or friction stir welding, and re-age after any thermal joining.
Can 7A77 be formed, bent or molded?
Built by laser powder bed fusion (typically 30–60 µm layers, N₂/Ar, preheated plate); Zr nucleant suppresses solidification cracking, but supports and low-angle overhangs still need care, and powder must be kept dry.
What surface finishes work on 7A77?
Blast/tumble then machine critical faces; clear or hard anodize is standard (colour is darker and less even than 6xxx), chromate/Ti-Zr conversion + primer for corrosion-critical parts, HIP first if a sealed anodic film is required.
7A77 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 |
|---|---|---|
| Zn7075 base composition | 5.1 – 6.1 | 5.6 |
| Mg | 2.1 – 2.9 | 2.5 |
| Cu | 1.2 – 2 | 1.6 |
| Zrnanoparticle nucleant added to the powder surface (7A77 functionalization); level is proprietary/process-dependent | 0.5 – 2 | 1 |
| Cr | 0.18 – 0.28 | 0.23 |
| Feimpurity max | ≤ 0.5 | 0.2 |
| Siimpurity max | ≤ 0.4 | 0.1 |
| Mnimpurity max | ≤ 0.3 | 0.05 |
| Tiimpurity max | ≤ 0.2 | 0.03 |
| Al | balance | — |
7A77 Stress Relieved — frequently asked
What is 7A77 Stress Relieved used for?
7A77 Stress Relieved is typically used for aerospace primary and secondary structures, defence hardware and weapon mounts, high-load fittings and lugs, missile and UAV structural components, motorsport chassis brackets and topology-optimised replacements for machined 7075. In short: aerospace 7000-series LPBF.
What is the yield strength of 7A77 Stress Relieved?
7A77 Stress Relieved has a typical yield strength of 270 MPa (39.2 ksi) and a tensile strength of 360 MPa (52.2 ksi) — stronger than 69% of aluminum grades. Strength varies by condition: see the 6 listed tempers.
Is 7A77 Stress Relieved easy to machine?
Reasonably — machinability is rated good (66/100, better than 66% of aluminum grades). Machines like 7075 — sharp uncoated carbide, high speed, generous coolant; expect springy thin walls and beware of subsurface porosity opening up on finish passes.
Can 7A77 Stress Relieved be welded?
Not readily — weldability is rated poor (25/100). Fusion welding of 7xxx is still discouraged (hot cracking, HAZ softening); use mechanical joints, adhesive, or friction stir welding, and re-age after any thermal joining.
What surface finishes work on 7A77 Stress Relieved?
Blast/tumble then machine critical faces; clear or hard anodize is standard (colour is darker and less even than 6xxx), chromate/Ti-Zr conversion + primer for corrosion-critical parts, HIP first if a sealed anodic film is required.
Can 7A77 Stress Relieved be formed, bent or molded?
Built by laser powder bed fusion (typically 30–60 µm layers, N₂/Ar, preheated plate); Zr nucleant suppresses solidification cracking, but supports and low-angle overhangs still need care, and powder must be kept dry.
What is the maximum service temperature of 7A77 Stress Relieved?
7A77 Stress Relieved is rated for continuous use to about 100°C (212 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 7A77 As Printed and 7A77-T6?
As Printed is the default condition — baseline condition straight off the LPBF machine; crack-free equiaxed structure but supersaturated and residually stressed — use only for form/fit or before heat treatment. T6: standard delivery condition for structural AM parts — gives strength close to wrought 7075-T6; least resistant to stress-corrosion cracking. Yield strength is 310 MPa in As Printed versus 480 MPa in T6.
Can FabDigit make parts in 7A77 Stress Relieved?
Yes — 7A77 Stress Relieved is available for 3D printing with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- 7A77.60L nanofunctionalized aluminium powder for additive manufacturing — HRL Laboratories (2021)
- 3D printing of high-strength aluminium alloys (Martin, Yahata, Hundley et al.) — Nature 549, 365–369 (2017)
- Aluminum Standards and Data / Teal Sheets — alloy 7075 registration — The Aluminum Association (2018)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- 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.