Cast Aluminum vs. Cast Iron – Which is Better?

Cast Aluminum vs. Cast Iron Which is Better

Do you need help choosing between cast aluminum vs. cast iron? This comparison article answers your selection queries. It delves into the manufacturing process of either material and, more importantly, their specific properties and application examples. Let’s begin by defining each.

What is Aluminum Casting?

Aluminum casting is the production of parts using the casting process. Pieces of an aluminum alloy are heated to their melting point (above 660 °C), and the melt is poured or forced into a mold.

Upon cooling, the metal solidifies, assuming the mold’s shape. The metal used is an alloy made by mixing aluminum with small amounts of silicon or copper and sometimes manganese or magnesium.

The alloys create lightweight but strong parts. As a result, the material has applications in many industries, including automotive and construction, as well as demanding ones like aerospace.

What is Iron Casting?

It means making parts by forming a molten iron alloy in a mold. The metal is placed in a furnace and heated until it melts into a liquid. The melt is then poured into a mold. Here, it cools and hardens into the required part.

The material is typically iron, with a carbon content above 2%. It has several forms: gray, ductile, white, and malleable. These alloys produce hard-wearing parts with very high tensile and compressive strengths.

An example of a part made by casting an aluminum alloy
An example of a part made by casting an aluminum alloy
Resource: https://makezine.com

Cast Aluminum vs. Cast iron

The two materials have distinct differences. Before choosing either, you should understand these differences. Here’s their comparison based on various properties, such as weight, strength, and others.

Weight

Aluminum is lighter, with a 2.7 g/cm3 density, compared to iron, which is specified at about 7.8 g/cm3. The lightweight nature of aluminum makes it usable in many applications requiring high-strength parts without introducing too much weight, such as automotive, construction, or aerospace.

Strength

An aluminum cast part is quite robust. But a cast iron type is even more robust, with higher tensile and compressive strengths. However, it’s a more brittle material and can fracture in lower temperatures. Overall, it performs better when it comes to strength.

Melting Point

The melting point of aluminum is 660 degrees Celsius (or 1220 degrees Fahrenheit), while that of iron is 1204 degrees Celsius (or 2200 degrees Fahrenheit). This means that iron can operate at higher temperatures. However, it requires more energy to produce.

Heat Conductivity

Aluminum generally has a higher thermal conductivity, with most alloys rated above 100 W/m k, compared to only 52 W/m k of iron. It conducts heat faster and takes a shorter time to cool after heating.

As a result, it suits applications where heat conduction and dissipation or distributions are significant considerations. On the other hand, iron has a higher heat retention capability.

Machinability

It’s easier to machine aluminum than iron alloys: it’s softer and less challenging to move about. The higher machinability makes the parts more straightforward to produce, reducing their overall cost. Iron is more difficult to cut into. This property reduces its manufacturability and increases the production cost.

Cost Difference

You use less energy to produce and transport aluminum despite being more expensive as a raw material. Iron alloys need more heat to melt. They also need specialized molds.

Being heavier, cast iron parts cost more to move from one place to another. These challenges make the material a more expensive option overall.

Part Durability

Iron has a higher strength and better wear resistance. But it’s also brittle and may fracture over time, mainly if used in harsh conditions. It also doesn’t resist corrosion, making it less durable in corrosive conditions.

Aluminum does not rust or crack easily in low temperatures, making it preferred in low heat or wet conditions. The surface of iron is usually given a corrosion-resistant coating to make it last longer.


Cast aluminum outdoor furniture
Cast aluminum outdoor furniture
Resource: https://www.youtube.com/watch?bFakOy8UFn0

Cast Aluminum vs. Cast Iron Advantages and Disadvantages

If you have to choose between cast aluminum and iron parts, you likely need help to make the right decision. That is because each material has both pros and cons. So here, we share our advice by looking at the advantages and disadvantages of either material.

Cast Aluminum Advantages and Disadvantages

Advantages

  • It’s lightweight
  • Costs less to produce
  • Has good machinability
  • Produces accurate parts and intricate designs
  • Has a high strength-to-weight ratio
  • Exceptional corrosion resistance

Disadvantages

  • Low compressive and tensile strength
  • High porosity

Cast Iron Advantages and Disadvantages

Advantages

  • High compressive and tensile strength
  • It has good wear resistance characteristics
  • Can retain heat for long

Disadvantages

  • It’s a brittle material
  • It’s prone to rusting
  • It costs more to manufacture and transport
Cast engine blocks
Cast engine blocks
Resource: https://youtu.be/dIjtap8GLF8?si=domoKGK4mH_6T8V5

Cast Aluminum vs. Cast Iron in Application

Given their different properties, you can expect the two materials to have slightly different applications. Here’s a look at the common uses of each and the reasons for its application.

Cast Aluminum Applications

  • Automotive: In automotive, the material produces lightweight auto parts that allow car manufacturers to improve performance and durability.
  • Furniture: Outdoor furniture is another widespread use. This furniture can stand up to damage by corrosion, in addition to being strong yet lightweight enough for mobility.
  • Medical: Many medical tools and devices, including scanning equipment and prosthetics, are made from aluminum.
  • Electronics: In the electronic industry, EMI shields, heat sinks, enclosures, and other components are made using the material.
  • Cookware: It heats up quickly and distributes heat well, making it a good material for lightweight and thin-walled cookware.
  • Aerospace: Aerospace parts are mainly made using this material, owing to its lightweight nature and dimensional stability, among other properties like part accuracy and design complexity.

Cast Iron Applications

  • Industrial Machinery: Used in constructing many industrial machines due to its hardness or density and wear resistance, among other properties.
  • Automotive: Some parts of automobiles are made from this material, including engine blocks.
  • Construction: It’s used in construction to create various parts, such as railings
  • Ornamental Structures: The applications of cast iron include making various sculptures and statues
  • Cookware: It has a higher heat retention capacity and distribution capability. These attributes make it suitable for making cookware like pans, oven parts, etc.
Testing cast iron vs. cast aluminum strength
Testing cast iron vs. cast aluminum strength
Resource: https://www.youtube.com/watch?v=BOEG_fv0G_c

Cast Aluminum or Cast Iron – Which is Better?

Each material is excellent in its own way, so your choice will largely depend on the specific application. For example, aluminum is your best option if you’re looking for lightweight parts without sacrificing strength.

Also, if you’re looking for a material you can use in wet, corrosive conditions since it doesn’t rust. We also suggest it if your parts require high precision and accuracy or are thin-walled. Iron is better if your part is used in high-stress conditions and subject to friction. It will last a long time since it’s exceptionally resistant to wear.

To make the best choice, consider the properties of each and determine if each characteristic fits your intended application. That way, you will have selected what best suits your project. Remember to choose a suitable alloy, too.

Conclusion

When choosing between cast aluminum and cast iron, it’s essential to consider their different characteristics. That’s because while both are popular, their properties make them different, which could significantly impact your project. Understanding their varied characteristics should help you make the right decision based on the pros and cons of each.

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