Once you have decided that the aluminum die casting process is suitable for your project, a crucial next step is deciding on the most appropriate alloy.
The aluminum alloy you choose will substantially impact both the casting process and the properties of the final product. Because of this, you must make your decision carefully and take an informed approach.
Read on to find out which characteristics are the most important when choosing an alloy for the die casting process and which are the most commonly used in die casting applications.
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Characteristics of Aluminum Die Casting Alloys
Determining the most suitable aluminum alloy for your application will mean weighing a wide array of characteristics. These comparative alloy characteristics follow the North American Die Casting Association’s guidelines, and we’ve divided them into two categories.
- The first category addresses alloy characteristics that affect the manufacturing process.
- The second covers characteristics affecting the properties of the final product.
We will cover some of the most important considerations below.
Alloy Characteristics Affecting the Casting Process
The alloy you choose for die casting directly affects several aspects of the casting process, like how easy the alloy is to work with and if it is prone to casting defects.
#1 Hot Cracking
Hot cracking, also known as solidification cracking, is a typical die casting defect for aluminum alloys that can result in internal or surface-level tears or cracks. This casting defect is generally attributed to thermally-induced internal stress and strain, which form during the solidification process as the cast contracts. Certain aluminum alloys are more susceptible to hot cracking than others, and your selection should consider this.
#2 Die Soldering
Another common defect found in the die casting of aluminum is die soldering, which is when the cast sticks to the die walls and makes ejection difficult. It can damage both the cast and the die, so you should look for alloys with high anti-soldering properties.
While other aspects could be relevant to your process, these are two of the biggest processing concerns when die casting different aluminum alloys. However, while choosing an easy-to-cast alloy will keep your production costs lower, you also need to consider how the alloy selection will affect the final product.
Alloy Characteristics Affecting the Final Product
It’s common for the most sought-after properties of an aluminum alloy to be its mechanical properties, especially strength, ductility, and hardness. These attributes are fundamental and are sure to impact your final decision significantly. However, there are several other important qualities as well.
#1 Corrosion Resistance
Corrosion resistance, which is already a notable attribute of aluminum, can vary considerably from alloy to alloy and is an essential characteristic to consider depending on the environmental conditions your product will be exposed to.
#2 Wear Resistance
Wear resistance is another property commonly sought in aluminum products and can differentiate some alloys. It can be crucial for applications where the part is subjected to constant friction. Thermal and electrical conductivity can also be necessary for certain applications.
#3 Surface Treatments & Machinability
Finally, cast products often need to receive a surface treatment or be further shaped after leaving the die. Some alloys will take up these treatments or post-cast procedures more easily than others, and it’s something you need to take into account before choosing an alloy.
Some of the most common surface treatments for both die-cast and extruded aluminum parts are anodizing, electroplating, powder coating, painting, and polishing. Other standard post-cast procedures for aluminum parts include cold and hot working, machining, and welding.
Most Common Aluminum Alloys for Cast Products
This section presents some specific aluminum alloys commonly used in die casting. These alloys are shown as named under the Aluminum Association system. If you’re unfamiliar with how casting aluminum grades are classified, you can read about it in our Aluminum Grades article.
According to the NADCA, the most popular alloys for die casting belong to the 3xx.x series, followed by the 4xx.x series, with alloys from the 5xx.x and 2xx.x series being somewhat less common but useful for specific applications.
The following table compares a few of the essential characteristics of popular aluminum alloys used in die casting. You can find specific technical values for each alloy at the featured links below.
| Alloy | Corrosion Resistance | Resistance to Hot Cracking | Anodizing | Machinability | Common Applications |
|---|---|---|---|---|---|
| A380 | Fair | Very Good | Good | Good | Workbench vises and other hand tools, gear cases, lawnmower housings |
| A360 | Excellent | Excellent | Good | Good | Instrument cases, irrigation system parts, outboard motor parts, hinges |
| 383 | Good | Excellent | Good | Very Good | Engine brackets, cylinder head covers, appliances, furniture, power tools |
| A413 | Excellent | Excellent | Good | Fair | Outboard motor pistons, dental equipment, street lamp housings |
| B390 | Fair | Good | Fair | Fair | Pistons, blocks, manifolds, and cylinder heads for internal combustion engines, brake cylinders |
| 518 | Excellent | Poor | Excellent | Excellent | Architectural castings, conveyor parts, marine and aircraft hardware fittings |
Which Alloy Should I Choose for my Project?
There isn’t a single alloy that will be the best for every application. Because of this, you should carefully consider which aspects are the most important for your project.
For example, alloy A380 is the most widely used casting alloy on the market and is suitable for many applications. Unfortunately, it underperforms when it comes to corrosion resistance, so depending on the application for your final product, A380 may not be the best option.
A360 is an alternative we use with many of our customers, and it performs much better in the area of corrosion resistance. It is more difficult to cast, but this challenge can be overcome in many circumstances. As such, we recommend that you consider A360 for most industrial applications.
In general, by noting which characteristics are more important for your specific situation, you will be able to tell more easily which alloy is best for your application. You can learn more about the die casting solutions Gabrian offers by looking at our die casting services page.
