ADC12 and A380 are the two most widely used cast aluminum alloy grades in the global pressure die-casting industry, but belong to different standard systems — ADC12 under Japan’s JIS standard, A380 under the US ASTM standard. This article compares the relative differences in chemical composition and mechanical properties, and offers concrete guidance on when to choose which grade.
Are ADC12 and A380 the same alloy under two different names?
This is a common question, and the short answer is: very similar, but not entirely identical. Both belong to the Al-Si-Cu (aluminum-silicon-copper) alloy system, developed along similar lines to serve high-volume pressure die-casting at reasonable cost. In most practical applications, the two grades can be considered equivalent and are accepted interchangeably by global automotive component suppliers.
However, this equivalence isn’t absolute. The JIS and ASTM standards specify different tolerance ranges for each element, resulting in small differences that can matter for applications demanding high precision in mechanical properties or corrosion resistance.
Comparing chemical composition
Both alloy grades belong to the Al-Si-Cu system, but the JIS and ASTM standards specify different tolerance ranges for each element. The table below presents the relative difference in trend between the two grades, based on metallurgical characteristics widely documented in the industry.
| Element | Comparative trend | Effect |
|---|---|---|
| Silicon (Si) | ADC12 tends to allow higher silicon content than A380 | Higher silicon content typically gives slightly better fluidity |
| Copper (Cu) | A380 tends to allow higher copper content than ADC12 | Higher copper content can give higher strength but reduces corrosion resistance |
| Iron (Fe) | Both standards specify a roughly similar maximum limit | Not a major distinguishing factor between the two grades |
| Magnesium (Mg) | ADC12 tends to allow slightly higher magnesium content | Negligible effect in most ordinary applications |
| Zinc (Zn) | A380 tends to allow significantly higher zinc content than ADC12 | Worth noting if the product is sensitive to zinc content in a specialized application |
The most notable difference lies in the trend of copper and zinc content. A380 tends to allow these two elements at higher levels, which can give somewhat higher mechanical strength in some cases, but also reduces corrosion resistance compared with ADC12 under the same environmental conditions.
Comparing mechanical properties
In terms of mechanical properties, the two alloy grades are more similar to each other than the compositional differences might suggest, since the mechanical properties of a pressure die-cast alloy depend heavily on cooling rate and actual casting parameters, not just theoretical chemical composition.
| Property | ADC12 | A380 | Note |
|---|---|---|---|
| Tensile strength | Equivalent, negligible difference under standard casting conditions | Equivalent | Actual difference depends more on casting parameters than the alloy grade itself |
| Elongation | Slightly higher in some cases | Equivalent or slightly lower | Not a deciding factor when choosing between the two grades |
| Corrosion resistance | Better than A380 thanks to lower copper content | Relatively lower than ADC12 | The clearest distinguishing factor between the two grades |
| Post-cast CNC machinability | Equivalent | Equivalent | No widely documented significant difference |
The key point to remember is: the mechanical property difference between ADC12 and A380 in actual production is often much smaller than the property variation between different batches of the same alloy grade, if casting-machine operating parameters aren’t controlled consistently. In other words, maintaining a stable casting process is usually more important than choosing between ADC12 and A380.
When to choose ADC12, when to choose A380
In most cases, the decision to choose ADC12 or A380 isn’t based on mechanical property differences, but on the standard the end customer requires. If the product is supplied to a Japanese customer or the drawing references the JIS standard, ADC12 is the default choice. If the product is destined for the North American market or the drawing references ASTM, A380 is the appropriate choice.
Where the product has no specific standard requirement from the customer and the business can decide on its own, two practical factors are worth considering: if the product is exposed to moisture or requires above-average corrosion resistance, ADC12 is typically slightly favored thanks to its lower copper content; if the factory already has a stable, optimized operating process for one of the two grades, maintaining that grade usually delivers more consistent quality than switching to chase a negligible mechanical-property difference.
When to consider an alloy grade other than ADC12/A380
Although ADC12 and A380 are the most common choices, there are specific cases where a different alloy grade should be considered rather than defaulting to one of these two.
If the product requires significantly higher corrosion resistance than either ADC12 or A380 can offer — for example, direct exposure to seawater or chemicals — consider an Al-Mg system alloy such as ADC6, covered in the previous article, despite the trade-off of harder castability.
If the product requires significantly higher mechanical strength after heat treatment, some other specialized alloy systems (outside the scope of these two common grades) may be more suitable — this is a case worth discussing specifically with the technical team rather than deciding based on general information alone.
Frequently asked questions
Can ADC12 be used to replace A380 in an order already signed under the ASTM standard?
Technically, the two grades are quite similar, but changing the alloy grade from what’s specified in the contract requires written approval from the customer first — it shouldn’t be substituted unilaterally even if you believe the two grades are equivalent.
Do ADC12 and A380 use the same casting temperature and machine operating parameters?
Broadly similar since both belong to the Al-Si-Cu system, but due to small differences in silicon and copper content, the optimal operating parameters (pouring temperature, pressure) may need slight adjustment when switching between the two grades to ensure consistent quality.
If the drawing only states “pressure die-cast aluminum” without specifying an alloy grade, which one should be chosen?
In this case, it’s best to proactively follow up with the customer to clarify which standard applies (JIS or ASTM) and the actual operating environment requirements, rather than choosing a default grade, since this information directly affects whether the customer will accept the product.
Contact Daiwa for detailed advice
If you need to convert a drawing between JIS and ASTM standards, or aren’t sure which alloy grade suits your product’s specific requirements, Daiwa’s technical team can advise based on your drawing, the customer’s required standard, and actual operating conditions.