# A356 vs ADC12 Aluminum Casting: A Procurement Engineer's Guide to Choosing the Right Alloy
Introduction
Selecting the wrong aluminum alloy at the project kickoff stage is one of the most expensive mistakes a procurement engineer can make. The choice between A356 and ADC12 — the two most widely specified cast aluminum alloys in North America and Europe — directly impacts tooling cost, cycle time, mechanical performance, and long-term field reliability. Get it right, and you unlock lighter parts, faster delivery, and lower unit cost. Get it wrong, and you face redesigns, scrap, and warranty claims. This guide breaks down A356 vs ADC12 aluminum casting in the practical terms a sourcing team actually needs.
A356 Aluminum Alloy Overview
A356 (AlSi7Mg0.3, equivalent to EN AC-42100) is a hypoeutectic Al-Si-Mg alloy designed for high integrity castings where mechanical performance and pressure tightness matter more than raw throughput.
Chemical composition (typical, wt%)
- •Si: 6.5–7.5
- •Mg: 0.25–0.45
- •Fe: ≤ 0.20
- •Cu: ≤ 0.20
- •Ti: ≤ 0.20
- •Al: balance
Mechanical properties (T6 temper)
- •Ultimate tensile strength: 262–290 MPa
- •Yield strength: 185–215 MPa
- •Elongation: 5–10%
- •Brinell hardness: 75–90 HB
- •Fatigue strength (5×10^8 cycles): ~90 MPa
Typical applications
- •Aerospace brackets and housings
- •Automotive wheels, knuckles, control arms
- •Hydraulic and pneumatic valve bodies
- •High-pressure pump housings
- •Medical and structural components requiring weldability
Process compatibility
A356 is ideally suited to gravity die casting, low-pressure die casting (LPDC), and sand casting. It responds excellently to T6 heat treatment, which is what unlocks its high strength and ductility. Learn more about our aluminum gravity casting capabilities.
ADC12 Aluminum Alloy Overview
ADC12 (JIS H5302, equivalent to A383 in the US and EN AC-46500 in Europe) is the workhorse of high-volume die casting. It is an Al-Si-Cu alloy formulated for excellent castability, dimensional stability, and high-speed production.
Chemical composition (typical, wt%)
- •Si: 9.6–12.0
- •Cu: 1.5–3.5
- •Fe: ≤ 1.3
- •Mg: ≤ 0.30
- •Zn: ≤ 1.0
- •Mn: ≤ 0.50
- •Al: balance
Mechanical properties (as-cast, F temper)
- •Ultimate tensile strength: 220–260 MPa
- •Yield strength: 140–160 MPa
- •Elongation: 1–3%
- •Brinell hardness: 75–85 HB
- •Excellent dimensional stability after casting
Typical applications
- •Consumer electronics housings and heat sinks
- •Power tool gear cases
- •Automotive transmission housings, oil pans, brackets
- •Motor end caps and frames
- •Telecom enclosures
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Process compatibility
ADC12 is engineered for high-pressure die casting (HPDC). Its narrow freezing range, excellent fluidity, and low shrinkage make it the default choice when cycle time and complex thin-wall geometry drive the bill of materials. Explore our die casting services.
A356 vs ADC12 Comparison Table
| Criterion | A356 (T6) | ADC12 (F) |
|---|---|---|
| Tensile strength | 262–290 MPa | 220–260 MPa |
| Yield strength | 185–215 MPa | 140–160 MPa |
| Elongation | 5–10% | 1–3% |
| Castability / fluidity | Good | Excellent |
| Pressure tightness | Excellent | Good |
| Weldability | Excellent | Poor (gas porosity) |
| Heat treatable | Yes (T6) | No (rarely) |
| Min. wall thickness | 3.0–4.0 mm | 1.0–1.5 mm |
| Tooling cost | Low–Medium | High |
| Unit cost (high volume) | Higher | Lower |
| Typical parts | Wheels, knuckles, valve bodies | Housings, heat sinks, oil pans |
| Recommended process | Gravity / LPDC / sand | High-pressure die casting |
Real-World Material Selection Scenarios
1. High-pressure hydraulic pump body (200 bar, 5,000 units/year)
Choose A356-T6 in low-pressure die casting. Pressure tightness, fatigue resistance, and the ability to machine sealing surfaces without exposing porosity are decisive. ADC12's porosity from entrapped gas is a leak risk.
2. Brushless DC motor housing (200,000 units/year)
Choose ADC12 in HPDC. Thin walls (1.5 mm), integrated cooling fins, mounting bosses, and tight cycle time economics all favor ADC12. Mechanical loads are modest and corrosion is controlled by powder coating.
3. EV battery tray cross-member (structural, crash-rated)
Choose A356-T6, low-pressure die cast or sand cast. Crash performance demands elongation above 7% and the ability to weld the part into a larger assembly. ADC12 cannot meet either requirement.
4. 5G base station heat sink (high volume, complex fins)
Choose ADC12 in HPDC. Thermal conductivity is comparable, fin geometry favors HPDC fluidity, and unit cost dominates. No structural load case requires A356.
5. High-pressure gas valve body (helium leak tested)
Choose A356 in gravity or low-pressure die casting. Helium tightness, weld repair option, and the ability to operate at elevated temperatures make A356 the only safe choice.
Decision Tree
- •IF the part must be pressure tight (hydraulic, pneumatic, fuel, gas) THEN A356.
- •ELSE IF the part is structural or safety critical and requires elongation > 5% THEN A356.
- •ELSE IF the part must be welded into a larger assembly THEN A356.
- •ELSE IF annual volume is below ~10,000 pieces and tooling budget is tight THEN A356 (gravity or sand).
- •ELSE IF the part has walls below 2 mm, complex thin features, or integrated heat sinks THEN ADC12.
- •ELSE IF the program is high volume (>50,000/yr) and unit cost dominates THEN ADC12.
- •ELSE default to ADC12 for cost, A356 for performance.
Frequently Asked Questions
1. Can ADC12 be heat treated like A356?
Generally no. ADC12 castings contain dissolved hydrogen and entrapped die-cavity gas; solution treatment causes blistering. Specialized vacuum or pore-free HPDC variants allow limited T5/T6, but it is not standard practice.
2. Is A356 more expensive than ADC12 per kilogram?
Ingot pricing is similar, but A356 finished parts usually cost more per piece because gravity and LPDC processes have longer cycle times and lower cavitation than HPDC.
3. Which alloy has better corrosion resistance?
A356 wins. Its low copper content gives noticeably better resistance to salt spray and general atmospheric corrosion. ADC12's 1.5–3.5% Cu reduces corrosion performance, which is why most ADC12 parts are coated.
4. Can I switch from ADC12 to A356 mid-program?
Only with a redesign. Wall thicknesses, draft angles, gating, and tolerances differ significantly between HPDC and gravity processes. Plan the alloy choice before tooling is cut.
5. What about A380, A383, or AlSi10Mg?
A380 and A383 are close North American cousins of ADC12. AlSi10Mg is an A356 alternative used heavily in European LPDC and additive manufacturing. Bohua can quote any of these — talk to our engineers about the right regional equivalent.
Get a Free Material Recommendation from Bohua Casting
Bohua Casting has supplied A356 and ADC12 components to North American and European OEMs for over 20 years across gravity, low-pressure, and high-pressure die casting lines. Send us your 3D model, annual volume, and load case, and our materials team will return a free alloy and process recommendation within 48 hours — including a DFM review and an indicative quote.
Contact Bohua Casting today to request your free material selection consultation.