7000-series aluminum (Al-Zn-Mg, often with Cu/Cr/Zr) is the highest-strength family of common wrought aluminum alloys. It can be precipitation-hardened to extreme tensile strengths, machines beautifully, and keeps weight low—yet it is generally not weldable (except for a few grades like 7005/7020 with strict procedures). You pick 7xxx when you must squeeze the most strength and stiffness out of the lightest part.
What is 7000 series aluminum?
What it is: Wrought aluminum alloys where zinc is the primary alloying element with magnesium (and often copper, chromium, zirconium). The magic is precipitation hardening (solution heat treat → quench → age), which locks tiny particles in the metal and boosts strength dramatically.
Why engineers choose it
- Top-of-class strength: Common grades in T6/T651 exceed 500–570 MPa UTS; elite grades go higher.
- High stiffness-to-weight: Same elastic modulus as other aluminums (~70 GPa), but far higher yield strength for a given mass.
- Excellent machinability: Produces clean chips and crisp edges; stable in stress-relieved tempers (-T651).
- Surface finish friendly: Hard-coat anodize and conversion coatings take well.
- Caveats: Poor fusion weldability for most grades; risk of stress-corrosion cracking (SCC) in some tempers; formability is limited in hard tempers.
When it beats 6000/5000
- Space is tight, loads are high, and parts will be machined or forged/extruded, not welded.
- Fatigue and stiffness matter more than deep drawability or as-welded corrosion performance.
What grades are in the 7000 series?
A quick buyer’s map of widely specified grades (you can trim this table to match stocked items):
| Grade | Main alloying | Typical forms | One-line note |
|---|---|---|---|
| 7005 | Zn-Mg | Extrusions, tubes | Weldable with post-weld heat treatment; used in bicycle frames. |
| 7010 | Zn-Mg-Cu-Zr | Plate, forgings | Aerospace structural plate & forgings; high toughness. |
| 7020 | Zn-Mg | Plate, extrusions | Weldable structural alloy for vehicles/marine; lower strength than 7075. |
| 7049 | Zn-Mg-Cu | Forgings | Landing-gear type forgings; high strength. |
| 7050 | Zn-Mg-Cu-Zr | Plate, forgings | Better SCC resistance & toughness than 7075, esp. in thick sections. |
| 7055 | Zn-Mg-Cu | Plate, extrusions | Very high strength for weight-critical aerospace parts. |
| 7068 | Zn-Mg-Cu-Zr | Bar, rod | Among the highest UTS wrought aluminums; premium fasteners/hardware. |
| 7075 | Zn-Mg-Cu-Cr | Plate, bar, extrusions | Classic high-strength workhorse; broad availability. |
| 7077 | Zn-Mg-Cu | Plate | High-strength plate applications. |
| 7085 | Zn-Mg-Cu | Thick plate | For thick-section aerospace; good toughness after quench. |
| 7150 | Zn-Mg-Cu-Zr | Plate | High strength/toughness combo. |
| 7175 | Zn-Mg-Cu-Cr | Forgings | 7075 forging counterpart; gear & strut components. |
| 7255 / 7475 | Zn-Mg-Cu (high purity) | Sheet/plate | Elevated fracture toughness for skins and panels. |
Common tempers you’ll see: T6/T651 (peak strength), T73/T74/T76 (slightly lower strength, better SCC resistance), T73xx/T74xx on thick sections, stress-relieved “-51” for machining stability.
7000 Series Aluminum and Die Casting
Quick take: 7xxx (Al–Zn–Mg–Cu) are high-strength wrought/forging alloys; 7xx.x casting options are rarely used for complex HPDC parts. If you need to “cast the idea,” accept a different alloy and design trade-offs.
- You cannot replicate 7075-T6 strength/fracture toughness in HPDC. Use AlSi10Mg-T6 and geometry (thicker sections, ribs, generous radii) to meet loads.
- For extreme strength, keep the part as wrought/forged + machining.
- Coatings (conversion + powder/e-coat) manage corrosion and appearance.
Wrought → Cast Substitutes
| Wrought intent | Castable substitute | Why / when |
|---|---|---|
| 7075 CNC housing (non-critical) | AlSi10Mg (T6) | Higher cast strength/toughness; good for machined datums |
| 7050 bracket concept | A380 / ADC12 | Complex geometry + cost advantage |
| Hard-anodize cosmetic | A380 + powder/e-coat | Coating stack provides wear/appearance |
Trying to convert a 7xxx billet/plate design to casting? We’ll quantify the trade-offs and propose an alloy/heat-treat + geometry that survives your loads.
Where do real buyers use 7000?
Aerospace & defense structures
- Parts: wing and fuselage skins (7475), stringers and ribs (7050/7150 plates), bulkheads and frames (7085 thick plate), landing-gear forgings (7049/7175), hard-mount brackets and lugs (7075/7050), missile/launcher frames (7068).
- What matters: high static strength, damage tolerance and fracture toughness, SCC resistance (T74/T76), certification against AMS/MMPDS, traceable heats.
- Forms: plate 10–150 mm; thick plate 150–250 mm; closed-die forgings; precision 5-axis machining from stress-relieved stock.
Performance automotive & motorsport
- Parts: upright/knuckle, hub carrier, steering rack housing, diff case inserts, brake caliper blocks, suspension rockers.
- Why 7xxx: maximum stiffness and fatigue limit at low mass; superb machining for tight tolerances; hard-coat anodize for wear.
- Grades: 7075-T6/T651 for billets; 7050 where toughness in thicker sections is critical.
Bikes, scooters & personal mobility
- Parts: MTB/BMX frames (7005/7020 weldable extrusions), stems, cranks, chainrings, folding-joint blocks (7075 plate).
- Notes: 7005/7020 allow welded frames with appropriate PWHT; 7075 parts are bolted or machined—not welded.
Robotics, automation & semiconductor tooling
- Parts: high-stiffness end-effectors, linear-stage carriages, vacuum plates, precision gantry beams, EOAT brackets.
- Requirements: low mass inertia, flatness after machining (-T651), clean, hard anodized surfaces.
Tooling, molds & fixtures
- Parts: blow-mold cavities, trim dies, CMM fixtures, weld fixtures, vacuum jigs.
- Why 7xxx: excellent machinability and dimensional stability; hard-coat anodize + PTFE for wear and release.
Marine (above-water, non-welded components)
- Parts: winch drums, spreader bars, foil-mast brackets, deck hardware, foil mast step blocks.
- Guidance: for welded hulls and structural plate choose 5xxx; for machined/bolted hardware 7075/7050 in SCC-resistant temper plus coating is common.
Fasteners & high-strength hardware
- Parts: bolts, nuts, inserts, couplers (7068/7075/7050), camera/optics mounts.
- Specs: thread-rolled vs machined, shot-peened surfaces, conversion coat + seal to mitigate SCC; controlled grain flow for forged fasteners.
How do 7000s form, machine, and weld?
Forming: Limited in hard tempers (T6). If bends are required, form in O/T4, then age to final temper.
Machining: Excellent. Use sharp carbide, positive rake; watch residual stress on non-stress-relieved stock; specify -T651 for stability.
Welding: As a rule, do not fusion-weld 7075/7050/7068—strength collapses and SCC risk rises. 7005/7020 can be welded with qualified procedures and post-weld heat treatment; mechanical fasteners/adhesives are preferred.
Heat treatment & tempers—what should you specify?
- T6/T651: solution heat-treated + aged (-51 stress-relieved). Highest strength; use for machined billets and plates where SCC risk is controlled by environment/coatings.
- T73/T74/T76 families: slightly lower strength, better SCC and exfoliation resistance—smart for marine/chemical or warm, humid service and for thick sections.
- Design hint: If parts see cyclic wet salt exposure or sustained tensile stress, move from T6 → T73/T74/T76 and add coating; or switch to 5xxx/6xxx if welding is required.
Surface finishing & corrosion control
- Anodizing: Type II for color/decorative, Type III hard-coat for wear.
- Conversion coatings/primers: Chromate-free or chromated conversion + epoxy primer improves SCC margin.
- Galvanic pairing: Avoid direct contact with stainless steel or carbon fiber; isolate with sleeves, gaskets, or coatings; drain any crevices.
7075 vs 7050: which should you pick?
- Strength: Both are very high; 7050 retains strength and toughness better in thick plate.
- SCC resistance: Edge to 7050 in T7451/T7651.
- Availability: 7075 wins for bars, tubes, extrusions, plate; 7050 is mostly plate/forgings.
- Cost & machining: 7075 is generally cheaper and machines slightly easier.
Rule of thumb: Thin to medium sections → 7075; thick, critical structures → 7050 (T74/T76).
Stock forms & typical size ranges
- Plate (7075/7050): 6–150 mm standard; 7085 thick plate up to ~250 mm.
- Sheet (7475/7075): ~0.8–6 mm for skins, panels.
- Bar/Rod (7075/7068): Ø6–200 mm common; larger by request.
- Extrusions (7005/7075): angles, channels, tubes, custom profiles for frames and machine structures.
Standards & equivalents (quick view)
- AA/ASTM: 7075-T6/T651, 7050-T7451/T7651, 7005-T5/T6, 7020-T651.
- AMS/MMPDS: typical callouts for aerospace plate/forgings (e.g., AMS 4045 for 7075-T6 sheet).
- EN designations: e.g., EN AW-7075 (AlZn5.5MgCu).
FAQs
Is 7075 stronger than steel?
Stronger than many mild and some alloy steels in tensile strength, but aluminum’s stiffness (E ≈ 70 GPa) is ~1/3 of steel. For the same deflection you still need section depth.
Can 7075 be anodized black?
Yes. For wear or sliding parts use Type III hard-coat; color depth varies with alloy/temper.
Why can’t I weld 7075 but I can weld 7005?
Copper-bearing 7xxx grades lose strength and become SCC-prone in the weld zone. 7005/7020 are Zn-Mg without Cu and can be welded with controlled procedures plus post-weld aging.
What temper should I use near saltwater?
Prefer T73/T74/T76 and add coating—or switch to 5xxx if you must weld or if the part holds sustained tensile stress in wet service.
Is 7068 the strongest aluminum I can buy?
It’s among the highest-UTS wrought grades, but availability, cost, and design data are more limited. For broad supply and data, 7075/7050 are safer choices.
Build lighter, stronger parts with the right alloy at YongZhu Casting
You don’t need a catalog of alloys—you need parts that pass validation.
We design-for-manufacturing and produce custom aluminum components: high-strength 7000-series machined parts and integrated aluminum die-cast housings when casting saves cost. Send your drawings, tolerance stack, loads, and annual volumes—our engineers will recommend the right 7xxx grade/temper, coatings, and a machining or casting plan that fits your budget and lead time.
Request a manufacturability review → We’ll reply with alloy/temper options, risks, and a quote-ready process plan.
