Aluminum AlSi9Cu3 vs CP-Al
Aluminum · grade comparison
Aluminum AlSi9Cu3 and CP-Al are both aluminum grades. AlSi9Cu3 is the stronger of the two: yield strength 165 MPa (23.9 ksi) against 55 MPa (7.98 ksi) for CP-Al, about 3.0 times as much; tensile strength follows at 300 MPa (43.5 ksi) vs 105 MPa (15.2 ksi). In exchange, CP-Al is the more ductile: elongation 38% versus 2% for AlSi9Cu3, and AlSi9Cu3 is harder (85 HB vs 28 HB). AlSi9Cu3 is stiffer (75 GPa vs 69 GPa) and CP-Al conducts heat better (200 W/m·K vs 110 W/m·K). On the shop floor, AlSi9Cu3 machines more easily (good vs poor), CP-Al welds better (excellent vs poor), and AlSi9Cu3 sits in a lower cost tier (standard, $$) than CP-Al (high, $$$$).
AlSi9Cu3Choose it when strength drives the design, or when the part is machined in volume.
CP-AlChoose it when the part is bent, formed or impact-loaded, or when it will be welded.
AlSi9Cu3 vs CP-Al: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all aluminum grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all aluminum grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Shear Modulus
Bulk Modulus
Tensile Strength (Ultimate)
Yield Strength (0.2% offset)
Elongation at Break
Shear Strength
Fatigue Strength (Endurance Limit)
Fracture Toughness (K_IC)
Charpy V-Notch Impact (RT)
Hardness, Brinell
Hardness, Vickers
Same in both: Poisson's Ratio 0.33
Physical
Density and transition temperatures.
Density
Melting Point (Solidus)
Liquidus Temperature
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Latent Heat of Fusion
Min Service Temperature
Same in both: Max Service Temperature (continuous) 150°C302 °F
Electrical
Conductivity and insulation.
Electrical Conductivity
Electrical Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Galvanic Potential (seawater, vs SCE)
Corrosion Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Machinability Rating (AISI 1212 = 100 %)
Weldability
Formability (cold)
Castability
Brazeability / Solderability
Polishability
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Water
Typical Recycled Content
Same in both: Embodied Carbon (primary production) 12.5 kg CO₂/kg
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Modulus of Resilience
Thermal Diffusivity
Thermal Shock Resistance Index
Strength versus weight
Yield strength against density for every aluminum grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | AlSi9Cu3 | CP-Al |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$ Standard | $$$$ High |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Both take the same 4 finishes: Electroless Nickel (EN), Epoxy Coating, Gold Plating, Silver Plating.
AlSi9Cu3 vs CP-Al — frequently asked
Is AlSi9Cu3 stronger than CP-Al?
Yes. AlSi9Cu3 has a typical yield strength of 165 MPa (23.9 ksi) against 55 MPa (7.98 ksi) for CP-Al — about 3.0 times as much. Tensile strength is 300 MPa (43.5 ksi) vs 105 MPa (15.2 ksi).
Which is cheaper, AlSi9Cu3 or CP-Al?
AlSi9Cu3 is the lower-cost material: it sits in the standard tier ($$) while CP-Al is high ($$$$). Part price depends far more on geometry, tolerance and quantity than on raw stock — upload a CAD file for a live quote.
Which is easier to machine, AlSi9Cu3 or CP-Al?
AlSi9Cu3. Its machinability rates good (62/100) against poor (32/100) for CP-Al; for welding the order is CP-Al first (excellent, 92/100) then AlSi9Cu3 (poor, 20/100).
Ready to make it?
Upload a CAD file and FabDigit prices the part in AlSi9Cu3 and CP-Al side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.