# How to Choose the Right Aluminum Alloy for Your Casting Project
Selecting the right aluminum alloy is one of the most consequential decisions in any casting project. The alloy you choose determines mechanical performance, corrosion resistance, machinability, cost, and even which casting process you can use. Get it wrong, and you face warranty failures, excess machining costs, or parts that simply do not perform.
This guide compares the four most commonly specified aluminum casting alloys �?A356, A380, ADC12, and ZL114 �?and provides a practical framework for matching alloy selection to your project requirements.
Why Alloy Selection Matters More Than You Think
Many procurement engineers default to whatever alloy their supplier recommends, or simply specify "aluminum" on a drawing. This approach creates problems:
- •Over-specifying an expensive alloy wastes money on parts that do not need premium properties
- •Under-specifying a cheap alloy leads to field failures, warranty claims, and customer dissatisfaction
- •Mismatching alloy to process �?for example, specifying a gravity casting alloy for a die casting mold �?creates manufacturing defects
The right approach is to start with your performance requirements and work backward to the alloy and process that delivers them most cost-effectively.
The Four Major Casting Alloys Compared
A356 (AlSi7Mg0.3) �?The Structural Performer
A356 is the most widely used aluminum alloy for gravity casting and permanent mold casting. It is the go-to choice when mechanical performance matters.
Key Properties (T6 Condition):
- •Tensile strength: 260�?10 MPa
- •Yield strength: 200�?60 MPa
- •Elongation: 5�?0%
- •Hardness: 75�?5 HB
- •Thermal conductivity: ~150 W/m路K
- •Density: 2.68 g/cm�?
Strengths:
- •Excellent response to T6 heat treatment, significantly improving strength and hardness
- •Superior corrosion resistance due to very low copper content (<0.05%)
- •Good weldability for post-casting assembly
- •Excellent surface finish after machining
Limitations:
- •Not suitable for high-pressure die casting (requires gravity or low-pressure processes)
- •Higher raw material cost than A380 or ADC12
- •Longer cycle times in gravity casting vs. die casting
Best Applications:
Automotive structural parts, motor housings, aerospace components, marine hardware, pump bodies, and any application requiring high strength with corrosion resistance.
A380 (AlSi8.5Cu3.5) �?The Die Casting Standard
A380 is the most popular aluminum alloy for high-pressure die casting in North America. It offers a balanced combination of castability, mechanical properties, and cost.
Key Properties (As-Cast):
- •Tensile strength: 310�?30 MPa
- •Yield strength: 160�?70 MPa
- •Elongation: 3�?%
- •Hardness: 80 HB
- •Thermal conductivity: ~96 W/m路K
- •Density: 2.71 g/cm�?
Strengths:
- •Excellent fluidity for filling complex thin-wall geometries
- •Good machinability with balanced hardness and chip-breaking characteristics
- •Lower cost than A356 due to wider composition tolerance
- •Good strength in as-cast condition (no heat treatment needed for many applications)
Limitations:
- •Cannot be effectively heat treated �?porosity from die casting causes surface blistering during T6
- •Moderate corrosion resistance �?copper content (~3.5%) reduces resistance compared to A356
- •Not recommended for marine or high-humidity environments without surface treatment
- •Limited weldability
Best Applications:
Electronic enclosures, automotive brackets and covers, power tool housings, general-purpose die cast components where moderate strength is sufficient.
ADC12 (AlSi11Cu2.5) �?The Asian Die Casting Workhorse
ADC12 is the dominant die casting alloy in Asian markets (equivalent to A383 in the US system). It is similar to A380 but optimized for higher silicon content.
Key Properties (As-Cast):
- •Tensile strength: 310�?20 MPa
- •Yield strength: 150�?65 MPa
- •Elongation: 2�?%
- •Hardness: 75�?5 HB
- •Thermal conductivity: ~92 W/m路K
- •Density: 2.74 g/cm�?
Strengths:
- •Superior fluidity and die filling compared to A380, excellent for thin-wall castings
- •Very good dimensional stability
- •Widely available in Asian supply chains with competitive pricing
- •Good hot-cracking resistance
Limitations:
- •Slightly lower mechanical strength than A380
- •Higher silicon content creates more tool wear during CNC machining
- •Cannot be heat treated effectively
- •Moderate corrosion resistance (copper content ~2.5%)
Best Applications:
Consumer electronics housings, automotive sensor brackets, LED heat sinks, thin-wall enclosures, and high-volume die cast parts sourced from Asian manufacturers.
For a deeper dive into ADC12 vs. A356, see our detailed alloy comparison guide.
ZL114A (AlSi7Mg0.55) �?The High-Performance Specialist
ZL114A is a Chinese-standard high-strength aluminum casting alloy, essentially an enhanced version of A356 with higher magnesium content. It is specified for applications where maximum mechanical performance is required.
Key Properties (T6 Condition):
- •Tensile strength: 310�?40 MPa
- •Yield strength: 250�?80 MPa
- •Elongation: 4�?%
- •Hardness: 90�?10 HB
- •Thermal conductivity: ~140 W/m路K
- •Density: 2.68 g/cm�?
Strengths:
- •Highest strength among common gravity casting alloys
- •Excellent fatigue resistance for cyclic loading applications
- •Good response to T6 heat treatment with tight process control
- •Superior performance in safety-critical applications
Limitations:
- •Requires precise melt treatment and degassing for optimal properties
- •Narrower process window than A356
- •Higher cost and more demanding quality control
- •Limited international recognition compared to A356 (primarily used in Chinese standards)
Best Applications:
Aerospace structural castings, military vehicle components, high-performance automotive parts (suspension, EV motor housings), and safety-critical industrial equipment.
Side-by-Side Comparison Table
| Property | A356-T6 | A380 (As-Cast) | ADC12 (As-Cast) | ZL114A-T6 |
|---|---|---|---|---|
| **Tensile Strength (MPa)** | 260�?10 | 310�?30 | 310�?20 | 310�?40 |
| **Yield Strength (MPa)** | 200�?60 | 160�?70 | 150�?65 | 250�?80 |
| **Elongation (%)** | 5�?0 | 3�? | 2�? | 4�? |
| **Thermal Conductivity (W/m路K)** | ~150 | ~96 | ~92 | ~140 |
| **Corrosion Resistance** | Excellent | Moderate | Moderate | Excellent |
| **Heat Treatable** | Yes (T6) | No | No | Yes (T6) |
| **Primary Casting Process** | Gravity/Low-pressure | Die casting | Die casting | Gravity/Low-pressure |
| **Relative Cost** | Medium-High | Low-Medium | Low-Medium | High |
| **Weldability** | Good | Poor | Poor | Good |
A Decision Framework: 5 Questions to Choose Your Alloy
1. Does Your Part Require Heat Treatment?
If your design requires T6 heat treatment for maximum strength and hardness, your choices narrow immediately to A356 or ZL114A. Both alloys respond well to solution heat treatment and aging, delivering significant improvements in mechanical properties.
A380 and ADC12 cannot be effectively heat treated when die cast, because trapped gas porosity expands during the solution treatment step, causing surface blisters and internal defects.
Rule of thumb: If the part needs T6, choose gravity casting with A356 or ZL114A.
2. What Are Your Mechanical Performance Requirements?
Match your strength requirements to the alloy's capability:
- •Standard structural parts (tensile > 250 MPa): A356-T6 is sufficient and cost-effective
- •High-performance structural parts (tensile > 310 MPa, high fatigue resistance): ZL114A-T6
- •Non-structural housings and covers (tensile > 280 MPa, as-cast): A380 or ADC12
- •Thin-wall enclosures with complex geometry: ADC12 (best fluidity)
3. Will the Part Be Exposed to Corrosive Environments?
Corrosion resistance is primarily determined by copper content:
- •A356 and ZL114A have very low copper (<0.1%), providing excellent corrosion resistance suitable for marine, outdoor, and underbody automotive applications
- •A380 (~3.5% Cu) and ADC12 (~2.5% Cu) have moderate corrosion resistance; parts exposed to moisture or salt require anodizing, powder coating, or other protective surface treatments
If your part will be installed outdoors, underbody, or in humid environments without surface coating, choose A356 or ZL114A.
4. What Is Your Production Volume?
Production volume influences both alloy and process selection:
| Volume Range | Recommended Process | Typical Alloys |
|---|---|---|
| 1�?00 pcs/year | [Sand casting](/blog/sand-casting-vs-gravity-casting) | A356, ZL114A |
| 500�?0,000 pcs/year | Gravity casting (permanent mold) | A356, ZL114A |
| 10,000�?00,000+ pcs/year | High-pressure die casting | A380, ADC12 |
For medium-volume production typical of industrial and specialty automotive applications, gravity casting with A356 offers the best balance of part quality and unit economics.
5. What Is Your Budget Constraint?
Alloy cost is just one component of total part cost. Consider:
- •A380/ADC12 die casting has the lowest per-part cost at high volumes, but tooling investment is significant ($30,000�?150,000+)
- •A356 gravity casting has moderate tooling cost ($5,000�?30,000) and is more economical at low-to-medium volumes
- •ZL114A commands a material premium and requires tighter process control, adding 10�?0% to part cost vs. A356
For cost-sensitive projects that still need good mechanical properties, A356-T6 gravity casting often represents the sweet spot.
Common Alloy Selection Mistakes
Mistake 1: Specifying A356 for Die Casting
A356 is designed for gravity and low-pressure casting. Attempting to die cast A356 results in excessive porosity and parts that cannot be heat treated. If you need die casting, use A380 or ADC12.
Mistake 2: Choosing A380 for Pressure-Tight Parts
A380 die castings typically contain micro-porosity that makes them unsuitable for hydraulic or pneumatic housings without impregnation. For pressure-tight requirements, choose A356 gravity casting �?the process inherently produces denser castings.
Mistake 3: Ignoring Post-Machining Requirements
ADC12's high silicon content (10�?2% Si) causes accelerated tool wear during CNC machining. If your part requires extensive machining, A356 or A380 may reduce total manufacturing cost despite higher material prices.
Mistake 4: Over-Specifying ZL114A
ZL114A delivers exceptional performance, but many applications are well-served by A356 at lower cost. Reserve ZL114A for parts where the additional 10�?5% strength gain justifies the cost premium �?typically aerospace, military, or safety-critical automotive components.
How Bohua Casting Helps You Choose
Alloy selection should not happen in isolation. At Bohua Casting, we work with procurement engineers from the quoting stage to recommend the optimal alloy-process combination for each project. Our approach includes:
- •Requirements analysis �?Understanding your mechanical, environmental, and volume needs
- •Alloy recommendation �?Matching requirements to A356, ZL114A, or other alloys in our portfolio
- •DFM review �?Ensuring part geometry is optimized for the chosen casting process
- •Prototype validation �?Producing sample castings with full mechanical testing to confirm alloy performance
We specialize in #0f1e3d]">A356 and ZL114A gravity casting with in-house [T6 heat treatment and CNC machining, delivering complete finished parts ready for assembly.
Conclusion
Choosing the right aluminum alloy is a decision that ripples through your entire product lifecycle �?from manufacturing cost to field reliability. By matching your performance requirements, production volume, and budget to the right alloy-process combination, you avoid costly mistakes and get parts that perform as designed.
Quick summary:
- •A356-T6 �?Best all-around gravity casting alloy for structural parts needing strength + corrosion resistance
- •A380 �?Standard die casting alloy for cost-effective high-volume production
- •ADC12 �?Asian die casting standard with excellent thin-wall capability
- •ZL114A-T6 �?Premium gravity casting alloy for maximum mechanical performance
Need help selecting the right alloy for your project? Contact our team with your part drawing and requirements �?we will provide a recommendation within 24 hours. You can also browse our casting capabilities or learn more about our facility.
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