Lightweight aluminium performance for space applications
High strength combined with excellent machinability and irradiation resistance for satellite structures: one rolled aluminium alloy for primary and secondary structure, panels and precision hardware.
Description
Space systems push materials to the limit: launch vibration and shock, corrosive attack, deep thermal cycling, ionizing radiation and missions lasting many years all act on the same part, which must stay light, strong, dimensionally stable and reliable throughout. AMAG CrossAlloy.57 is designed for high-performance aluminium structures in this environment, with long-term radiation tolerance as the distinguishing property.
Since the presented data was assessed by general standards, the material performance needs to be verified and expanded in accordance with design and test guidelines relevant to the space industry, which would be pursued in cooperation with a strong partner in old or new space industry.
The CrossAlloy.57 advantage
- High strength-to-weight performance : Lighter structural components while maintaining stiffness, robustness and load-carrying capability.
- Designed for long mission life : Reliable performance in demanding orbital environments: thermal cycling, radiation exposure and dynamic load cases.
- Manufacturing efficiency : Excellent machinability and warm formability allow integrated features, local stiffening and reduced machining effort.
- Good joining and weldability : Robust brackets, inserts, interfaces and panel integration with reduced assembly complexity.
- Reduced material waste and complexity : Shift selected components from billet machining toward formed-sheet concepts, reducing scrap, lead time and cost.
Chemical Composition
The performance rests on the crossover chemistry: a high-magnesium 5xxx base made age-hardenable, hardening via the T-phase instead of the η-phase. Current internal specification limits and typical measured values are shown below.
| wt-% | Si | Fe | Cu | Mn | Mg | Zn | Cr | Ti | Zr |
|---|---|---|---|---|---|---|---|---|---|
| Min | – | – | 0.40 | 0.20 | 4.30 | 3.20 | – | – | – |
| Max | 0.40 | 0.40 | 0.70 | 0.45 | 4.90 | 3.60 | 0.20 | 0.15 | 0.10 |
| Typical | 0.15 | 0.21 | 0.50 | 0.32 | 4.65 | 3.43 | 0.06 | 0.02 | < 0.01 |
Remainder Al; other elements ≤ 0.10 each / ≤ 0.20 total.
Mechanical Behavior
Specific strength drives lighter primary structure and thinner tank walls. CrossAlloy.57 reaches Rp0.2 values up to 480 MPa (T6): it positions itself above damage-tolerant 2024-T3 (~345 MPa), in the range of thick-section 7050-T7451 (~455–490 MPa), and below lithium-bearing 2195 (~560+ MPa) – all without lithium and with markedly better formability and weldability.
For HFQ/SPF processed parts the service behavior can be tuned within the provided range by modification of processing and heat-treatment parameters to accommodate a use-case-specific performance profile.
Typical values are shown below; establishing customer specifications is feasible upon request.
Strip / sheet 1.0 – < 6.0 mm
| Property | T4-FH1) | after HFQ/SPF | T6 | T76 | T73 |
|---|---|---|---|---|---|
| Rp0.2 (MPa) | 260–310 | 255–400 | 450–480 | 380–410 | 310–340 |
| Rm (MPa) | 430–470 | 440–500 | 510–540 | 470–500 | 430–460 |
| A (%) | 18–23 | 11–18 | 9–12 | 10–13 | 11–14 |
1) FH: Pre-treated after solutionizing and quenching to ensure optimal grain structure, limited natural aging and fast hardening during subsequent aging
Plate 6.0 – 75.0 mm
| Property | T451 | T6151 | T651 | T7651 | T7351 |
|---|---|---|---|---|---|
| Rp0.2 (MPa) | 270–300 | 370–390 | 440–470 | 370–400 | 300–330 |
| Rm (MPa) | 440–470 | 470–490 | 510–540 | 470–500 | 430–460 |
| A (%) | 20–25 | 12–16 | 8–12 | 9–13 | 11–14 |
Reference alloys in the field for comparison:
| Property | 2024 (T3) | 7050 (T7451) | 2195 (T8) | 7475 (T761) |
|---|---|---|---|---|
| Rp0.2 min (MPa) | 285–290 | 434–441 | 538 | 421 |
| Rm min (MPa) | 400–440 | 503–510 | 565 | 490 |
| A min (%) | 8–14 | 9–10 | 6 | 9 |
Minimum values according to EN 485-2, aggregated over the thickness span shown for CrossAlloy.57, and MMPDS-2025 (Design values, A-/S-basis, longitudinal).
Bendability
Formed sheet parts need tight, crack-free bends. T4-FH bends readily but requires subsequent heat treatment to establish preferential in-use conditions; peak-aged T6/T651 needs a larger radius.
EN ISO 7438: Minimum bending radius to reach 90° without cracking, axis in rolling direction
| Thickness t | CA57 (T4-FH) | CA57 (T6) | CA57 (T451) | CA57 (T651) | 2024 (T3) | 6061 (T6) | 7075 (T651) |
|---|---|---|---|---|---|---|---|
| 0.5–1.5 mm | 1.5 t | 2.0 t | – | – | 4.0 t | 2.5 t | 5.5 t |
| 1.5–3.0 mm | 2.5 t | 3.0 t | – | – | 4.0 t | 3.5 t | 6.5 t |
| 3.0–6.0 mm | – | – | 2.0 t | 3.0 t | 5.0 t | 4.0 t | 8.0 t |
Reference values according to EN 485-2 (minimum bending radius for 90° bending, informative).
Fracture Toughness
Damage tolerance is a design driver for fracture-critical primary structure, where a flaw must not grow to failure between inspections. The naturally aged T451 is the toughest condition and peak-aged T651 the least; the overaged T7651 sits between the two, and a batch composition optimized for toughness lifts it further.
ASTM E399: Plane-strain fracture toughness, compact-tension (CT) geometry
| Material | KIc T-L (MPa√m) | KIc L-T (MPa√m) | Rm (MPa) |
|---|---|---|---|
| CrossAlloy.57-T451 | 34–38 | 39–43 | ~430 |
| CrossAlloy.57-T651 | 18–22 | 25–30 | ~520 |
| CrossAlloy.57-T7651 | 21–25 | 27–33 | ~500 |
| CrossAlloy.57-T76511) | 28–30 | 39–41 | ~500 |
| 7075-T6512) | 24 (20–30) | 29 (22–33) | ~550 |
| 7075-T76512) | 25 (22–31) | 32 (24–47) | ~525 |
| 7075-T73512) | 30 (23–52) | 33 (27–40) | ~500 |
1) Batch composition optimized for high fracture toughness.
2) MMPDS-2025, Table 3.1.2.1.4 (plate): average of the reported data, min–max range in brackets.
Fatigue
Launch vibration and years of load cycling make fatigue life a primary design driver. CrossAlloy.57 tracks typical 7xxx aerospace alloys and clearly outperforms 2024, an assessment confirmed by a major aircraft OEM. The chart overlays CrossAlloy.57 test points on the aerospace handbook reference bands according to AIMS, MMPDS and HSB.
CrossAlloy.57 fatigue test points against aerospace reference data: notched (Kt=2.3) vs. AIMS 2124-T851, 7175-T7351 and 7050-T7651; unnotched (Kt=1) vs. MMPDS 7475-T7351 and HSB 2024-T351 clad.
Forming & Machining
For thick-plate space and structural hardware the primary route is machining: CrossAlloy.57 machines with exceptionally low distortion due to minimal residual stress and without hot spots, enabling uniform in-service performance. For thinner structures other forming routes might be more suitable: superplastic forming (SPF) for the most complex geometries and hot-form quenching (HFQ) for high-strength formed parts, while cold forming covers structures with low complexity, where the ductility and bendability of T4-FH/T451 are sufficient. This lets integrally stiffened panels and tank domes be formed in one piece rather than assembled from many parts.
Corrosion
For space hardware, stress-corrosion cracking (SCC) is the make-or-break property. CrossAlloy.57 sits between the 5xxx and 7xxx alloys in SCC performance and is tunable by temper: the highly overaged/SCC-optimized condition T7351 reaches > 480 h, while peak-aged T651 is the SCC-weak point, the classic strength/SCC trade-off.
Similar to the mechanical behavior, corrosion resistance for HFQ/SPF formed components depends on the utilized processing and heat-treatment parameters.
| Condition | ASTM G67 (NAMLT) | ASTM G110 (IGC acc. 2xxx/7xxx) | ASTM G44/G47 (SCC) |
|---|---|---|---|
| T451 / T4-FH1) | < 5 mg/cm³ | < 100 µm | – |
| T6151 | < 10 mg/cm³ | < 100 µm | NA |
| T651 / T61) | < 20 mg/cm³ | < 100 µm | < 100 h |
| T7651 / T761) | < 30 mg/cm³ | < 100 µm | NA |
| T7351 / T731) | < 15 mg/cm³ | < 100 µm | > 480 h |
NA = not yet available; the required test duration has not been reached. Detailed SCC investigations are ongoing.
1) Conditions without cold work (T4-FH, T6, T76, T73) not separately evaluated; similar performance expected based on historical data for standard alloys.
Anodizing
Space hardware is anodized for corrosion protection during ground handling and storage and, in chromic- or sulfuric-acid variants, to set thermo-optical surface properties. CrossAlloy.57 anodizes without process adaptation: thin sheet in T4-FH develops a homogeneous, streak-free layer. On thick plate the grain structure becomes more pronounced towards mid-thickness, which is normal for high-strength wrought alloys and is seen in the same way on 7xxx grades. Where the anodized surface is optically or thermally relevant, the layer should be qualified on the final geometry.
Anodizing trials: 1.0 mm sheet in T4-FH with a homogeneous, streak-free surface, and step samples from 25.0 mm (pickled and clear-anodized) and 75.0 mm plate (pickled only).
Radiation Tolerance
Over a mission's lifetime, energetic radiation can dissolve the hardening precipitates of a conventional aluminium alloy and soften it. In heavy-ion irradiation experiments, CrossAlloy.57's T-phase precipitates (T651/T7651) show virtually no dissolution or coarsening even at 2.0 dpa, whereas 6061-T6 fully dissolves its precipitates at 0.2 dpa (−80 % Rp0.2).
EDX maps (Mg, Zn) and TEM dose series (0.0 to 2.0 dpa) for CrossAlloy.57 in T651 and T7651: the T-phase precipitates remain stable across the full irradiation range.
Joining
Certain space structures are welded assemblies, so weld efficiency at domes, nozzles and transitions decides the design. CrossAlloy.57 is compatible with space-qualifiable friction stir welding and behaves much like 5xxx alloys for arc welding; GMAW/GTAW were tested on 6/10/25/38.1 mm with no hot cracking. Weld-performance figures are indicative and require validation for specific use cases.
| Process | Result (T651) | Note |
|---|---|---|
| FSW | > 75 % Rm retained | joint vs. base material, confirmed on 2, 3 and 6 mm |
| GMAW/GTAW | > 65 % Rm; up to 85 % Rm | 85 % with matching filler wire + post-weld heat treatment |
Physical Properties
| Property | min–max | mean |
|---|---|---|
| Density ρ (g/cm³) | 2.71–2.72 | 2.71 |
| Young's modulus E (GPa) | 70.3–73.0 | 71.7 |
| Shear modulus G (GPa) | 26.3–27.5 | 26.6 |
Potential use cases for CrossAlloy.57
Proposed applications are indicative and derived from cross-correlation between available material data and market research. They reflect where CrossAlloy.57 could add value from our perspective; given the limited information available to us, actual suitability is application-specific and is confirmed in cooperation with partners.
Satellite primary structures
Main frames, bus structures, brackets, housings and structural sandwich-panel concepts requiring high stiffness, low mass and dimensional stability.
Precision mounting for optical instruments
Stable benches, mounts and instrument structures for optics, sensors, star trackers and high-resolution payloads.
Small propellant tanks
Small welded propellant and pressurant tank shells for satellites, where high specific strength and weldability enable lighter, demisable aluminium tanks as an alternative to titanium; propellant compatibility is validated per application.
Available Dimensions
| Thickness | Max. width (mm) | Max. length (mm) |
|---|---|---|
| 1.0–2.0 mm | ||
| T4-FH | 1650 | 4000 |
| T6 / T76 / T73 | 1500 | 6000 |
| 2.0–6.0 mm | ||
| T4-FH (up to 3.0 mm) | 2000 | 10000 |
| T6 / T76 / T73 | 1500 | 6000 |
| 6.0–12.0 mm | ||
| all Tx51 tempers | 1500 | 6000 |
| 12.0–150.0 mm | ||
| all Tx51 tempers | 1500 | 6500 |
Conservative assessment based on prototype production and limited number of lots. Additional dimensions available upon request.