A356 aluminum is widely used cast aluminum alloy in the Al–Si–Mg family. Many components in the automotive and aerospace industries use A356 for structural castings, housings, impellers, and more.
If you are evaluating A356 for your project, continue reading. This article teaches you the properties of A356 and the guidelines.
Nomenclature, standards, and equivalents
If you want to acquire A356 alloy of aluminum, it corresponds to the following designations:
- AA – A356
- ASTM – A356.0
- SAE – 356.0
- UNS – 356.0 A13560
- AMS – A356.0: 4218
- International – EN AC-42000
Chemical Composition / Alloying Elements
You can produce A356 by alloying aluminum with silicon, magnesium, and a few trace elements. Silicon produces a smooth grain flow, improving the casting response of your alloy. Magnesium, in comparison, makes your A356 strong enough to withstand precipitation hardening.
Below is the full chemical composition chart of Aluminum 356:
| Element | Typical / Allowed Range | Comments / Role |
| Si (Silicon) | 6.5 – 7.5 % | Increases fluidity, lowers melting range, improves castability, and reduces shrinkage. |
| Mg (Magnesium) | 0.25 – 0.45 % | Allows age-hardening (Mg₂Si precipitates) to strengthen the alloy under T5/T6. |
| Fe (Iron) | ≤ 0.20 % | Impurity; too much Fe reduces ductility, promotes brittle intermetallics. |
| Cu (Copper) | ≤ 0.20 % | Slightly increases strength but may reduce corrosion resistance. |
| Mn (Manganese) | ≤ 0.10 % | Helps counteract the negative effects of iron by forming intermetallics that are less harmful. |
| Zn (Zinc) | ≤ 0.10 % | Minor effect; usually residual. |
| Ti (Titanium) | ≤ 0.20 % | It is often added as a grain refiner to refine the microstructure. |
| Other (each) | ≤ 0.05 % | Minor residuals. |
| Other (total) | ≤ 0.15 % | All residual impurities. |
| Al (Aluminum) | Balance (~91.1–92 % or higher) | The matrix element. |
Variants (A356.2 vs A356.0)
A356.1 is a higher quality grade of A356 aluminum that offers superior tensile strength, elongation, and hardness. Although it is slightly more expensive, A356.1 justifies the higher material cost due to its reliability in demanding applications.
Physical & Thermal Specifications
These are the physical specifications of A356 Aluminum:
- Density: The average density of Aluminum alloys is 2.68 g/cm³.
-
- Melting point: solidus/liquidus): A356 alloy has a melting range around 554 °C to 615°CC
- Thermal conductivity: A356 alloy exhibits an average thermal conductivity rating of 151 W/m.K
- Coefficient of thermal expansion: The thermal expansion rate of A356 is 21.4 × 10⁻⁶ /°C.
- Electrical conductivity: A356 alloy has an IACS rating of 33% to 36%.
- Specific heat capacity: A356 alloy has a heat capacity of 944 to 982 J/Kg.C
Mechanical Properties of A356
The mechanical properties of A356 aluminum are:
As-Cast (F, or “as poured”) Condition
As-Cast A356 refers to A356 as it is immediately after casting and without any heat treatment. In this state, A356 exhibits the following properties.
- Tensile strength of 150-180 MPa
- Yield strength of 90-120 MPa
- Elongation of 2-6% (depends on porosity or casting quality)
- Hardness of 60 – 70 Brinell
Heat-Treated Conditions: T5, T6
Since A356 is age-hardenable, most high-performance applications use a heat-treated state (T5, T6) for improved strength.
- T5: You can produce the T5 temper of A356 by allowing your metal to cool naturally. Next, you artificially age it a an elevated temperature.
- T6: In comparison, you can produce T6 A356 by allowing the metal to cool, then heating it at elevated temperatures. Afterward, you must quickly quench the castings and then move them to another oven for solution treatment.
| Property | T5 | T6 |
| Tensile strength | 25.0 | 37.0 |
| Yield strength | – | 26.0 |
| Elongation | – | 5.0 |
| Brinell Hardness | 55-85 | 70-100 |
In permanent mold casting, commercial A356-T6 exhibits 37 ksi tensile strength, 26 ksi yield strength, and ~5 % elongation.
Therefore, you should opt for A356-T5 when superior durability is a factor in your application. A356-T5, in contrast, offers moderate strength and hardness since it’s artificially aged without solution treatment.
Fatigue Strength, Creep,
A356-T6 offers fatigue strength ranges that are comparable to the 6061 grade of aluminum. However, these values vary based on the cast integrity and surface finish. Many sources agree that A356-T6’s fatigue strength ranges from 90 to 120 MPa, which is superior to T5 temper.
In addition, since cast Al-Si-Mg alloys like A356 are not usually applied at extreme homologous temperatures, creep is not prevalent. These allos only begin to degrade and lose stability at elevated temperatures above 150 °C.
High-Temperature Performance
T5 and T6 tempers of A356 are stable up to approximately 170 °C. Beyond this temperature, creep and stress relaxation can become problematic for long-term use.
Microstructure & Effect of Processing
The microstructure of your A356 consists of α-Al dendrites surrounded by eutectic silicon particles. In T6, silicon particles are spheroidized and uniformly distributed. This makes your alloy tougher compared to the coarse, acicular silicon characterized by as-cast A356.
Casting Behavior & Machinability
Here, you discover the casting and machining behaviours of your A356 alloy.
Castability and Solidification
If you work with cast aluminum parts, A356 is one of the best alloys you can select. The metal’s low melting point and excellent fluidity ensure your cast fills the mold accurately. It also presents a lower risk of shrinkage compared to many similar alloys.
Due to these traits, you can subject A356 to sand casting, permanent mold casting, or squeeze casting. But the cast method ultimately depends on the strength and precision required for the final part.
Machining / CNC Workability
It is relatively easy to machine T5 and T6 tempers of A356, since they produce smooth chips. However, it is advised to use high-speed steel or carbide cutting tools when machining this alloy. That way, you can maintain an excellent surface finish while reducing the risk of tool wear.
Welding & Joining
A356 alloy offers excellent welding properties, and you can achieve a great finish using techniques such as MIG and TIG. However, when you are welding this aluminum alloy, watch out for cracks or hot zones.
Since A356 is commonly used in transportation, you must anneal or treat welded castings to prevent sudden failures. For more details, check the guide on welding and joining Aluminum.
Strength Comparison & Other Alloys
In this section, we compare A356 aluminum with common alternative alloys.
A356 vs 6061
| Property | 6061-T6 | A356-T6 (or good cast) |
| Ultimate Tensile Strength | ~260 – 310 MPa (varies) | ~250 – 300 MPa (in many castings) |
| Yield Strength | ~240 – 290 MPa | ~180 – 230 MPa (typical) |
| Elongation / Ductility | 8 %–12 % (depending on thickness) | ~3 %–6 % in many castings |
| Fatigue Behavior | Good (for wrought) | In many cases, A356 has comparable or slightly better fatigue due to cast microstructure (depending on finishing) |
| Thermal / Physical | Wrought 6061 has higher thermal conductivity and a slightly higher coefficient of expansion. | A356 has lower expansion and good conductivity (though lower than 6061) |
Compared to A356, 6061 alloy has higher thermal conductivity and a higher expansion coefficient. This makes A356 superior for engine parts because it can better maintain dimensional stability. Equally, 6061 temperature properties make it ideal for heat exchangers or appliances needing fast heat transfer.
In addition, 6061 is widely used in structural frames, aerospace components, and high-performance tubing. Meanwhile, A356 alloy finds wide application in detailed automotive and aerospace parts thanks to its casting and strength properties.
A356 vs 319 (and other Al casting alloys)
For high-pressure cast applications, select A356 over 319 Al alloy. This is because A356 contains more silicon and magnesium, making it stronger and more corrosion-resistant. In comparison, 319 aluminum is better suited for general engine and transmission castings or when cost is a factor during casting.
Equivalent Alloys / Substitute Alloys
A356 can sometimes be replaced with 357 when higher ductility is needed. 357 has slightly different magnesium and silicon ratios for improved toughness.
For forged or machined parts, 6061 can serve as a substitute for A356 when casting isn’t required. The choice usually depends on whether your part’s complexity, production volume, and heat treatment needs favor a cast or wrought process.
Limitations, Trade-offs & Common Misconceptions
A common misconception is that A356 is weak simply because it’s cast. But when properly processed and heat-treated, its strength is close to that of wrought alloys like 6061. However, A356 can have micro-porosity and lower ductility, which limit its use in high-impact or heavily stressed parts.
The key trade-off is between cost and performance.A356 offers excellent value and flexibility for complex shapes, while 6061 remains superior for uniform, high-precision structural applications.
Applications & Use Cases
Examples of A356 alloy appliances.
Aerospace Applications
A356’s strength-to-weight ratio proves to be useful in aircraft components like:
- Brackets
- Shells
Automotive Applications
- Wheels
- Cylinder heads
- Engine blocks
- Pistons
- Suspension components
Industrial & Consumer Uses
A356 alloy also finds extensive use in factories due to its corrosion and fatigue strength. These components include:
- Housings
- Pump parts
- Heat exchangers
- Frames
- Enclosures
- Impellers
- Propellers
Die Casting & Investment Castings
Although A356 can be die cast, it is not a suitable alloy for this manufacturing process. The reason for this is that die-cast A356 cannot achieve the T6 heat-treated condition, which limits its mechanical properties.
In comparison, A356 investment cast offers a superior dimensionally finish and the capacity for heat treatment. But investment casting for A356 is rare compared to sand or permanent casting.
Ingot & Raw Material Supply
A356 raw alloy is commercially available in ingots and billets. However, manufacturers may melt new ingots with scrap aluminum when the primary goal is to reduce costs.
Supply-wise, A356 aluminum is easy to order across key industrial regions such as China. It also costs $1700 per ton on average. Factors such as aluminum material fluctuations and demand spikes may cause the price of A356 alloy to increase.
Price, Market & Procurement Perspectives
The main factor that affects aluminum sourcing costs is the base price of aluminum ingots or costs. The next big factor is the cost of alloying silicon and other elements with A356, as well as the manufacturing processes required for your appliance.
Furthermore, prices of A356 alloy vary across geographical regions. Therefore, sourcing may be cheaper in regions like China and Pakistan, where recycled aluminum is widely available.
Lastly, when buying A356, check all material certifications like melt records, chemical composition, and heat treatment history. This way, you can ensure the alloy meets all your specifications. Also, confirm whether the material is supplied in blocks or casts, as this can affect machining performance.
Conclusion
In conclusion, A356 is an aluminum alloy that proves to be useful in casting automotive and aerospace parts. If you are evaluating whether to use A356 in your next project, consult JieJia CNC for a detailed quote.
FAQs:
How does porosity affect the strength and fatigue life of A356 castings?
Porosity acts as a strength concentrator, reducing the cross-sectional area of your A356 castings. This process lowers tensile strength and significantly reduces fatigue life.
What non-destructive testing methods can detect internal defects in A356 parts?
If you want to check defects in your A356 castings, X-ray radiography and computed tomography (CT) are good testing methods. Ultrasonic testing can also identify voids and inclusions, depending on part geometry.
What is the typical artificial aging schedule for A356-T6?
After solution heat treatment and quenching, A356-T6 is artificially aged at 155–165°C (311–329°F) for 5–8 hours. This promotes precipitation hardening.
How stable are A356’s properties under elevated or cyclic temperature exposure?
A356 loses strength above ~150°C due to over-aging. Therefore, if your appliance withstands prolonged cyclic thermal exposure, its mechanical properties will slowly start to degrade.
Can A356 aluminum be recycled/remelted without significant property loss?
Yes, you can remelt and reuse A356. However, pay close attention to the impurities and hydrogen content to maintain quality across your workpieces. Excessive recycling without refining may also increase porosity and reduce properties.
Related articles:
Polypropylene Melting Point: Numbers, Methods, And Processing
Is Iron Magnetic? Domains, Curie Point, And Diagnostic Approach
ABS Melting Point: Thermal Behavior, Processing & Design Tips
