If you are machining a thick-walled structural component — a wing spar, a bulkhead fitting, or a landing gear rib — and 7075-T651 is maxing out on section thickness, 7010-T7651 can deliver higher through-thickness strength with better fracture toughness and stress-corrosion resistance in sections over 100 mm. It is not a drop-in replacement for 7075; it was designed specifically for heavy plate applications where quench sensitivity kills the performance of leaner 7xxx chemistries. This article lays out what 7010 is, what its certified properties look like, how to machine it without scrapping expensive plate, and what to put on your RFQ drawing.
Grade Identity, Standards, and Nomenclature
7010 is a heat-treatable aluminum-zinc-magnesium-copper wrought alloy in the 7xxx series. It was developed in the UK by Alcan in the 1970s as a premium alternative to 7075 for thick plate and open-die forgings. Unlike 7075, which loses strength rapidly in sections beyond ~60–75 mm due to quench sensitivity, 7010 uses a Zr (zirconium) grain-refinement strategy instead of Cr (chromium), which improves hardenability and preserves properties through the full section.
| Standard | Designation | Product Form |
|---|---|---|
| EN 573-3 | EN AW-7010 [AlZn6MgCu] | Wrought alloy — plate, forging |
| ISO 209 | AW-7010 | Plate, extrusion, forging stock |
| AMS 4203 | 7010-T7651 Plate | Aerospace plate, 12.7–101.6 mm |
| AMS 4204 | 7010-T7451 Plate | Aerospace plate, 25.4–152.4 mm |
| AMS 4205 | 7010-T7351 Plate | High-corrosion-resistance tempers |
| DIN 2633 / EN 2633 | 3.4394 (numeric) / AlZn6MgCu | Aerospace die forgings |
| BS L 169 / L 170 | 7010 Forging Stock / Forgings | UK aerospace legacy specifications |
| GB/T 3190 | 7A09 (near-equivalent, not identical) | Chinese standard — composition differs |
Important: GB/T 7A09 is often listed as a “7010 equivalent,” but the Chinese grade uses Cr grain refinement rather than Zr and carries different Fe/Si limits. Do not substitute 7A09 plate for 7010 without requalifying mechanical properties and SCC performance through the full section thickness.
Temper Designations and Supply Condition
7010 is almost always supplied in one of three over-aged tempers. Solution treatment is typically performed at 470–480°C followed by water quenching, then a controlled two-step artificial aging cycle. The T7x tempers deliberately over-age the alloy past peak strength to achieve stress-corrosion-cracking (SCC) resistance in the short-transverse (ST) direction — the critical failure mode for thick aerospace plate.
| Temper | Aging Route | Typical Section Range | Primary Property Trade-off |
|---|---|---|---|
| T7651 | Two-step over-age, stress-relieved by stretch (1.5–3% permanent set) | 12.7–101.6 mm (AMS 4203) | Highest strength among T7x; SCC resistance adequate for most structure |
| T7451 | Two-step over-age, stress-relieved by stretch | 25.4–152.4 mm (AMS 4204) | Intermediate strength + improved fracture toughness |
| T7351 | Two-step over-age, stress-relieved by stretch | Up to 152.4 mm (AMS 4205) | Maximum SCC resistance; 10–15% strength penalty vs T7651 |
The “51” suffix means stress-relieved by controlled stretching after solution treatment. Without this, thick plate would distort severely during machining as residual quenching stresses release asymmetrically. For any CNC part cut from plate thicker than 25 mm, always specify a stress-relieved temper on the drawing.
Chemical Composition per EN 573-3
| Element | Weight % | Role in the Alloy |
|---|---|---|
| Zn | 5.7–6.7 | Primary strengthening element; forms MgZn2 precipitates |
| Mg | 2.1–2.6 | Co-strengthener with Zn; controls precipitate volume fraction |
| Cu | 1.5–2.0 | Increases strength and SCC resistance; forms Cu-rich precipitates at grain boundaries |
| Zr | 0.10–0.16 | Grain refiner and recrystallization inhibitor; replaces Cr for better quench response |
| Fe | ≤ 0.15 | Impurity; forms Al7Cu2Fe constituents that reduce toughness |
| Si | ≤ 0.12 | Impurity; promotes Mg2Si, lowering fracture toughness |
| Mn | ≤ 0.10 | Minor dispersoid former; kept low to avoid quench-rate interference |
| Cr | ≤ 0.05 | Intentionally minimized; 7010 uses Zr instead |
| Ti | ≤ 0.06 | Grain refiner in cast ingot; negligible in wrought product |
| Others (each) | ≤ 0.05 | — |
| Others (total) | ≤ 0.15 | — |
| Al | Remainder | Balance |
The Zr-vs-Cr distinction is the single most important compositional feature of 7010. Chromium forms coarse Al12Mg2Cr dispersoids that promote quench-induced precipitation of η (MgZn2) on dispersoid interfaces during slow cooling from solution temperature. Zirconium forms coherent, nanometer-scale Al3Zr dispersoids that pin grain boundaries without acting as heterogeneous nucleation sites for η. This keeps more solute in solution through the quench, producing a finer, more uniform precipitate distribution after aging — exactly what you need when the center of a 150 mm plate cools 40–60°C slower than the surface.
Typical Mechanical Properties — 7010-T7651 Plate
Values below are minimums per AMS 4203 for plate 12.7–76.2 mm thick, tested at room temperature per ASTM E8 / ISO 6892-1. Properties degrade slightly with increasing section thickness; always request certified mill test reports (MTR) for your specific plate gauge and lot.
| Property | Longitudinal (L) | Long-Transverse (LT) | Short-Transverse (ST) |
|---|---|---|---|
| Tensile Strength, Rm (MPa) | ≥ 495 | ≥ 475 | ≥ 450 |
| Yield Strength, Rp0.2 (MPa) | ≥ 430 | ≥ 410 | ≥ 380 |
| Elongation, A5 (%) | ≥ 8 | ≥ 6 | ≥ 4 |
| Compressive Yield Strength (MPa) | ≥ 420 | ≥ 400 | — |
| Shear Strength (MPa, typical) | 290–310 | — | — |
| Bearing Strength, e/D=2.0 (MPa, typical) | 690–740 | — | — |
| Modulus of Elasticity (GPa) | 71 | 71 | 71 |
| Shear Modulus (GPa) | 27 | 27 | 27 |
| Poisson’s Ratio | 0.33 | 0.33 | 0.33 |
| Density (g/cm3) | 2.82 | ||
| Melting Range (°C) | 475–635 | ||
Fracture toughness (ASTM E399, L-T orientation, T7651 plate 25–75 mm): KIC ≥ 24 MPa√m (minimum). For T7451 at 75–100 mm, expect 29–35 MPa√m. These values matter when your part contains sharp internal corners, snap-ring grooves, or threaded features that act as stress concentrators.
Fatigue: Smooth-specimen S-N data (R=0.1, axial, L-direction, T7651, 25 mm plate) shows fatigue strength of approximately 160–180 MPa at 107 cycles. Notched fatigue (Kt=3.0) drops to roughly 70–90 MPa at the same life. Design to the notched curve for any feature with a fillet radius below 0.5 mm.
Corrosion and Stress-Corrosion Cracking
7010 in T7651 has good resistance to general atmospheric corrosion, comparable to 7075-T73. However, it is a copper-bearing 7xxx alloy, which means:
- Galvanic corrosion is a real risk when 7010 contacts steel, titanium, or CFRP in the presence of an electrolyte (seawater, condensation, hydraulic fluid). Always specify a conversion coating (MIL-DTL-5541 Type I Class 1A chromate, or Type II non-chromate where regulations require) plus epoxy primer per MIL-PRF-23377 on mating surfaces.
- Exfoliation corrosion resistance is good in T7651 and excellent in T7351. AMS 4205 (T7351) parts are routinely specified for carrier-based aircraft where salt fog exposure is continuous.
- SCC threshold in ST direction (ASTM G47, alternate immersion in 3.5% NaCl): T7651 ≥ 240 MPa (75% of ST yield); T7351 ≥ 290 MPa (approaches 90% of ST yield). If your part carries sustained tensile stress in the short-transverse direction — a lug with a pressed-in bushing, or a bolted joint with high preload — specify T7351 or require SCC testing per ASTM G47 on a production-lot sampling basis.
- No self-passivation like stainless. 7010 will corrode if the coating system is damaged. Do not leave machined parts in bare-metal storage for more than 48 hours in humid conditions without temporary preservative (MIL-PRF-16173 Grade 2 or equivalent).
CNC Machining 7010: What Actually Happens at the Spindle
7010 machines more like a gummy 7xxx than a brittle one. The copper content (1.5–2.0%) makes the chip slightly tougher and more abrasive than 6061 or 6082. Chip control is the primary challenge — at high feeds, 7010 produces long, stringy chips that bird’s-nest around the tool if chip breakers are not dialed in.
Starting-Point Cutting Parameters
These are reference starting points for a modern 20+ kW CNC machining center with rigid fixturing, through-spindle coolant, and balanced toolholders. Adjust based on your machine, tooling, workpiece stiffness, and tolerance requirements. No parameter is a guarantee of surface finish or tool life.
| Operation | Tool Type | Cutting Speed (m/min) | Feed (mm/rev or mm/tooth) | Depth of Cut (mm) |
|---|---|---|---|---|
| Rough turning | Carbide, K10/K20 uncoated or PVD TiB2 | 250–400 | 0.20–0.40 mm/rev | 2.0–6.0 |
| Finish turning | Carbide, fine-grain K10, polished flute | 350–500 | 0.08–0.15 mm/rev | 0.25–1.0 |
| Rough milling (face/shoulder) | Carbide, 2–3 flute, 45° lead angle | 300–600 | 0.15–0.30 mm/tooth | 2.0–5.0 (radial 50–70%) |
| Finish milling | Carbide, 2–3 flute, sharp edge, uncoated | 400–800 | 0.05–0.12 mm/tooth | 0.3–1.0 (radial 5–10%) |
| Drilling (dia 3–12 mm) | Solid carbide, polished flute, 130–140° point | 100–200 | 0.08–0.25 mm/rev | — |
| Drilling (dia 12–25 mm) | Carbide-tipped or solid carbide | 80–160 | 0.15–0.35 mm/rev | — |
| Tapping (M3–M12) | HSS-E spiral-point or spiral-flute, TiCN coated | 15–30 | Pitch-dependent | — |
| Reaming | Solid carbide, 6-flute, 45° helix | 30–60 | 0.20–0.50 mm/rev | 0.10–0.25 (stock) |
Why the Wide Speed Ranges
- Coated carbide inserts (TiB2, DLC, or ZrN) allow the upper end of the speed range. Uncoated polished carbide runs cooler at the lower end and produces better surface finish on finishing passes.
- Minimum quantity lubrication (MQL) works well for milling 7010 — the alloy’s thermal conductivity (~150 W/m·K) carries heat into the chip effectively. Flood coolant is preferred for deep-hole drilling (over 5×D) and tapping to prevent built-up edge.
- Workpiece rigidity matters enormously. A thin-walled pocket machined from 7010-T7651 plate can chatter at 400 m/min when a solid block machines cleanly at 600 m/min. Reduce speed and radial engagement when wall thickness drops below 3 mm.
Tool Wear Patterns and Countermeasures
7010 with Zr dispersoids causes abrasive flank wear rather than catastrophic chipping. You will see gradual wear-land development. The Zr-bearing Al3Zr particles (10–30 nm) are harder than the aluminum matrix and act as a fine polishing medium against the tool flank. Monitor flank wear and change inserts at 0.3 mm wear-land width for roughing, 0.2 mm for finishing.
Built-up edge (BUE) is the main quality killer on 7010. Because the alloy is relatively ductile in the T7x condition, aluminum can cold-weld to the tool rake face at speeds below ~200 m/min or when coolant delivery is inadequate. If you see a shiny deposit on the insert after a cut, increase speed by 20–30% and check coolant nozzle alignment. Uncoated polished carbide resists BUE better than most coatings on this alloy.
Heat Treatment and Stress Relief During Machining
7010 is supplied in the solution-treated, quenched, and aged condition. You do not heat-treat it after machining — the T7x temper is the final condition. However:
- Do not exceed 180°C during any post-machining process (baking of paint, adhesive cure, NDI penetrant drying). Exposure above the aging temperature — even for 30 minutes — will over-age the alloy further, permanently reducing strength.
- Stress redistribution during machining is the hidden problem in thick plate. Even T7651 stress-relieved plate retains residual stress gradients. When you machine a pocket 50 mm deep into one face of a 100 mm plate, you release asymmetric residual stress, and the part bows. Strategy: rough both faces equally before finishing, leave 2–3 mm stock per face, then alternate finishing passes to maintain symmetry.
- Vibratory stress relief has limited effect on age-hardened aluminum. Do not count on it to correct distortion from asymmetric machining.
Surface Treatments
| Treatment | Specification | Typical Use | Notes |
|---|---|---|---|
| Chromic acid anodizing (CAA) | MIL-A-8625 Type I | Fatigue-critical structure, bonded joints | Thinnest coating (2–5 μm); minimal fatigue debit |
| Sulfuric acid anodizing (SAA) | MIL-A-8625 Type II | General corrosion protection, paint base | 5–15 μm; Class 1 undyed, Class 2 dyed |
| Hard anodizing | MIL-A-8625 Type III | Wear surfaces, sliding fits | 25–50 μm; reduces fatigue strength by 10–30%; mask threads and fillets |
| Chemical conversion coating | MIL-DTL-5541 Type I / II | Electrical bonding, low-cost protection | Conductive; minimal dimensional change; not a substitute for anodizing |
| Primer + topcoat | MIL-PRF-23377 + MIL-PRF-85285 | External aircraft structure | Epoxy primer + polyurethane topcoat; full system required |
Masking requirement: When anodizing 7010 parts, mask all threaded holes, press-fit bores, and bearing seats. Anodic coating thickness must be specified on the engineering drawing — do not leave it to the plating shop. For fatigue-critical parts, specify CAA (Type I) rather than SAA (Type II) and note the fatigue debit on the stress analysis.
Where 7010 Is Used (and Why Not 7075)
7010 lives in thick-section aerospace primary structure. If you are machining thin sheet (under 6 mm), you should not be using 7010 — you will pay a premium for through-thickness properties you cannot exploit.
- Wing spars and ribs: Sections 80–150 mm thick where 7075-T651 plate would fail minimum tensile requirements at mid-thickness. The Airbus A330/A340 and several military platforms use 7010-T7651 extensively in the wing box.
- Landing gear structural components: Bulkheads, trunnion mounts, actuator attachment fittings. T7351 temper is common here for maximum SCC resistance under sustained load from hydraulic pressure and touchdown impact.
- Bogie beams and axle beams: Large forgings where section thickness rules out 7075. 7010-T7451 forgings (under AMS 4204/4205 scope) provide fracture toughness in the ST direction that 7075 simply cannot match beyond 75 mm.
- Helicopter rotor head components: High-cycle fatigue loading demands the combination of moderate strength with good fracture toughness and SCC resistance. 7010-T7451 is a standard material in several rotorcraft specifications.
- Pressurized fuselage frames: Where circumferential frames are machined from thick plate rather than built up from sheet, 7010 provides weight savings over steel alternatives while meeting damage-tolerance requirements.
Comparisons: 7010 vs 7075 vs 7050 vs 7040
Choosing between these alloys is about section thickness, strength target, and damage-tolerance philosophy.
| Property | 7010-T7651 | 7075-T651 | 7050-T7451 | 7040-T7651 |
|---|---|---|---|---|
| Typical plate range (mm) | 25–150 | 6–75 | 25–150 | 50–200 |
| L-direction YS (MPa, min) | 430 | 460 | 420 | 430 |
| ST-direction YS (MPa, min) | 380 | Not specified >75 mm | 380 | 390 |
| KIC L-T (MPavm, min) | 24 | 22 | 28 | 26 |
| SCC resistance (ST) | Good (T7651) | Poor (T651) | Very good | Good |
| Quench sensitivity | Low (Zr) | High (Cr) | Low (Zr) | Very low (Zr) |
| Relative cost | $$ | $ | $$$ | $$$ |
Decision rule: If your section is 60 mm or thinner and you need maximum strength, use 7075-T651. If your section is 60–150 mm and you need balanced strength + damage tolerance, use 7010-T7651 or 7050-T7451 (7050 has better fracture toughness but slightly lower strength). If your section exceeds 150 mm or you need the absolute best ST properties, consider 7040-T7651. None of these are interchangeable without requalification.
What to Include in Your RFQ Package
For a CNC-machined 7010 part, your drawing and RFQ should include:
- Full material call-out: “7010-T7651 per AMS 4203” (not just “7010” or “Aluminum 7010”). Include plate gauge and grain direction requirements (e.g., “Grain direction L to run parallel to part length”).
- Tolerances: Reference ISO 2768-mK or ASME Y14.5 with specific GD&T call-outs. Do not blanket-specify ±0.01 mm on all features without justification — machining cost scales with tolerance.
- Surface finish: Specify Ra per ISO 4287 or ASME B46.1. Typical: Ra 3.2 μm for general machined surfaces, Ra 0.8 μm for sealing faces and bearing bores.
- Surface treatment: Anodize per MIL-A-8625 Type I/II/III, specify masking requirements on drawing. Include primer and topcoat specification if applicable.
- Inspection requirements: Which dimensions require CMM report? Any FPI (fluorescent penetrant inspection per ASTM E1417) requirement? Any conductivity check per ASTM E1004 to verify temper?
- Quantity and delivery: Prototype quantity vs production lot. Lead-time expectations with realistic allowance for mill material procurement (7010 plate is not a stock item at most service centers).
- Certifications: MTR per EN 10204 3.1 or equivalent. Any requirement for first-article inspection (FAI) per AS9102?
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- 2024 Aluminum CNC Machining Guide: Properties, Speeds and Feeds
- MIL-A-8625 Anodizing: Types, Specifications and Process Selection
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