Scalmalloy®
metalaluminium alloy — Al-Mg-Sc-Zr
Al-Mg-ScAl-Mg-Sc-ZrAPWorks ScalmalloyScalmalloy RP
Composition — APWorks EP2886242B1 (European Patent)
| Element | Min % | Max % | Notes |
|---|---|---|---|
| Al | bal. | balance | |
| Mg | 4.00 | 4.900 | Primary solid-solution strengthener |
| Sc | 0.60 | 0.800 | Nucleation agent; precipitates Al₃(Sc,Zr) dispersoids on ageing |
| Zr | 0.20 | 0.500 | Enhances coarsening resistance of Al₃Sc dispersoids; stabilises grain structure to higher temperatures |
| Mn | 0.30 | 0.800 | Solid-solution strengthening and corrosion resistance |
| Fe | — | 0.400 | |
| Si | — | 0.400 |
Mechanical & thermal properties — 3 conditions
| Property | LPBF as-built (XY) | LPBF aged 325°C / 4h (XY) — primary service condition | LPBF aged 325°C / 4h (Z) |
|---|---|---|---|
| Elastic modulus | 68–74 GPa | — | — |
| Yield strength (0.2%) | 340–400 MPa | 440–520 MPa | 410–485 MPa |
| Ultimate tensile strength | 400–470 MPa | 480–560 MPa | 460–540 MPa |
| Elongation at break | 12.0–20.0 % | 9.0–17.0 % | 8.0–16.0 % |
| Hardness (HV) | — | 140–170 HV10 | — |
| Fatigue strength | — | 155–215 MPa | — |
| Density | 2.67 g/cm³ | — | — |
| Relative density | 99.0–99.9 % | — | — |
| CTE | 16.0–17.5 µm/m·K | — | — |
| As-built surface Ra | 7.0–18.0 µm | — | — |
Values shown as min–max where a spread is reported, otherwise as typical ± unit. Ranges reflect inter-source variation, not single-sample scatter. All values are for AM-processed specimens unless noted.
Engineering considerations
- Ageing is mandatory for structural use: 325°C / 4h. This can be performed on parts still attached to the build plate to relieve residual stress simultaneously. Do not exceed 350°C or 6h — dispersoid coarsening rapidly degrades properties.
- No solution treatment required — unlike conventional precipitation-hardened Al alloys (6000, 7000 series). The LPBF rapid solidification traps Sc/Zr in supersaturated solid solution, so ageing directly is sufficient.
- Parameter development: Scalmalloy is more tolerant of VED variation than AlSi10Mg. However, oxygen in powder or build atmosphere causes preferential Sc oxidation — maintain O₂ < 500 ppm, ideally < 200 ppm.
- Fatigue design: use machined-surface fatigue data (not as-built) for design calculations. As-built surface Ra 10–18 µm reduces fatigue limit by ~50% vs. machined. Vibratory finishing or electropolishing recommended for fatigue-critical surfaces.
- Powder reuse: limited data on Scalmalloy powder reuse. Treat as sensitive to oxygen pick-up. Characterise each reuse lot to ASTM F3049. APWorks recommends ≤10 reuse cycles.
- Cost justification: cost per kg is very high. Use in topology-optimised designs where the mass savings (vs. AlSi10Mg or Ti-6Al-4V) and fatigue performance justify the material cost premium. Typical application: aerospace bracket where Ti-6Al-4V is over-specified but AlSi10Mg fails fatigue.
- Corrosion protection: Scalmalloy has inherently better corrosion resistance than Al-Si alloys but standard aerospace coatings (anodising, chromate conversion, primer) should still be applied for corrosive environments.
Advantages
- Highest strength-to-density ratio of any commercial LPBF aluminium alloy — ~30–40% stronger than AlSi10Mg at same density
- Excellent fatigue resistance — far superior to Al-Si alloys due to equiaxed microstructure and absence of brittle Si eutectic
- Low anisotropy — equiaxed grains from Sc nucleation reduce XY/Z strength difference to <8%
- Good weldability and compatibility with conventional Al fabrication methods for hybrid structures
- Simple ageing cycle: 325°C / 4h in air — no complex solution treatment or quench required
- Superior corrosion resistance vs. Al-Si alloys — high Mg content forms protective oxide; no Si-phase galvanic cells
- No hot-cracking — Sc grain refinement eliminates the solidification cracking susceptibility of high-Mg Al alloys
Limitations
- High cost — Scalmalloy powder is 10–20× more expensive than AlSi10Mg due to Sc content (Sc is a rare earth element at ~$2,000/kg)
- Proprietary alloy — APWorks/Airbus holds patents; limited powder supplier competition constrains pricing
- No published ASTM or ISO material specification — qualification cost is higher than for standardised alloys
- Maximum service temperature ~150°C — Al₃(Sc,Zr) dispersoids coarsen rapidly above 300°C
- Parameter sensitivity — LPBF parameters must be optimised for each machine; green laser may offer advantages (not yet widely validated)
- Limited creep resistance — not suitable for high-temperature structural applications
- Ageing temperature must be controlled ±10°C to avoid under- or over-ageing
Typical applications
Aerospace structural brackets and secondary structure — typical design goal: equivalent strength to AlSi10Mg at 25% less materialUAV (drone) frames, motor mounts, and structural componentsSatellite structures and optical instrument mountsHigh-performance motorsport suspension components and gearbox bracketsLightweight structural topology-optimised parts where fatigue governs designDefence unmanned systems and lightweight weapon system mountsHeat exchangers where high specific strength and thermal cycling resistance matter
Industries
aerospacedefencemotorsportindustrial
Standards & certifications
ASTM-F3318established
Wrought Al specification referenced for comparison — no dedicated AM Scalmalloy standard exists yet
aerospace
No ASTM or ISO AM standard specifically for Scalmalloy. Aerospace qualification follows OEM-specific qualification plans using ASTM F3122 as framework.
Compatible AM processes (1)
Other metal materials
Ti-6Al-4V Grade 5titanium alloy — alpha-betaTi-6Al-4V ELI (Grade 23)titanium alloy — alpha-beta (extra low interstitial)CP-Titanium Grade 2commercially pure titanium — alphaCP-Ti Grade 4titanium — commercially pure alphaTi-6Al-2Sn-4Zr-2Motitanium alloy — near-alpha316L Stainless Steelaustenitic stainless steel304L Stainless Steelaustenitic stainless steel17-4PH Stainless Steelmartensitic precipitation-hardening stainless steel15-5 PH Stainless Steelmartensitic precipitation-hardened stainless steel420 Stainless Steelmartensitic stainless steelAlSi10Mgaluminium-silicon alloy (cast grade adapted for AM)AlSi7Mg Aluminium Alloyhypoeutectic Al-Si-Mg precipitation-hardenable aluminium alloyAlSi12aluminium — hypoeutectic/eutectic Al-SiInconel 718nickel superalloy — precipitation-hardenedInconel 625nickel superalloy — solid-solution-strengthenedInconel 939nickel superalloy — γ'-precipitation-hardened (high Al+Ti)Hastelloy® Xnickel superalloy — solid-solution strengthenedWaspaloy®nickel superalloy — γ'-precipitation-hardenedHaynes 282nickel superalloy — γ' precipitation-hardenedCoCrMocobalt-chromium alloy (biomedical and aerospace grade)Maraging Steel MS1 (18Ni-300)maraging steel (ultra-high-strength, precipitation-hardened)M300 Tool Steel (18Ni-300 Maraging Steel)maraging steel — tooling grade (ultra-high-strength, precipitation-hardened)H13 Tool Steelchromium-molybdenum hot-work tool steelCuCrZrcopper alloy — precipitation-hardenedCu-CP (Commercially Pure Copper)copper alloy — commercially pureCuSn10 (Bronze)copper alloy — tin bronzeGRCop-84copper alloy — dispersion/precipitation strengthenedInvar 36iron-nickel low-expansion alloyNiTi / Nitinolnickel-titanium shape-memory alloy
Related calculators
VEDCompute LPBF VED from power, scan speed, hatch, and layer thickness. Includes process windows for common alloys.Melt PoolLPBF / DED melt pool depth, width, and cooling rate from the Rosenthal moving heat source solution. Absorptivity, thermal diffusivity, and solidification velocity.DistortionEstimate residual stress and distortion risk index (σ/σ_y) for LPBF and DED builds. Mercelis-Kruth model with preheat sensitivity table.FatigueS-N curve estimation for AM metals using the Basquin law. Accounts for surface roughness stress concentration (Kt from Ra), build direction anisotropy, and porosity factor.Build Time EstimatorPer-process build time from part volume, layer count, and machine throughput. LPBF, SLS, FDM, SLA, DED, binder presets included.LPBF Porosity PredictorPredict lack-of-fusion and keyhole porosity from laser parameters. Maps VED and normalised enthalpy to relative density and flags dangerous regimes.Powder Characterisation TrackerScore a powder batch against key qualification metrics — particle size distribution, flowability, apparent/tap density, moisture, and oxygen content.Surface Treatment SelectorRank post-print surface treatments (shot peening, electropolishing, tumbling, PVD, and more) against Ra target, material, fatigue criticality, and corrosion requirements.NDT SelectorSelect the right non-destructive testing method for your AM part. Inputs: material class, defect focus, geometry, production volume, and criticality. Ranked scorecard across CT, X-ray, UT, FPI, MPI, eddy current, and visual inspection with detection limits and standard references.Laser ParamsDerive LPBF process parameters from target VED and melt-pool stability constraints. Power–speed–hatch–layer sensitivity matrix with keyholing and balling risk zones.
Last reviewed: 2026-05-13 · v1 · Sources: apworks-scalmalloy-2023, spierings-2017-scalmalloy, awd-2018-scalmalloy-fatigue, debroy-2018-review
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