Comparing 356 Aluminum vs 6061 Aluminum in Centrifugal Casting: A Case Study

Introduction:

Johnson Centrifugal was recently approached by a customer to compare centrifugally cast aluminum alloys for a proprietary application. In the realm of metal casting, choosing the right material is critical to achieving desired outcomes. This blog post delves into the properties and performance of two commonly used aluminum alloys, 356 and 6061, in our centrifugal casting process.

Background:

At JCT, our centrifugal casting involves pouring molten metal into a spinning vertical mold, where centrifugal force distributes the metal evenly, creating strong, dense parts. Aluminum alloys are favored for their lightweight properties, corrosion resistance, and strength-to-weight ratio. Among the plethora of aluminum alloys available, 356 and 6061 stand out for their distinct characteristics. Let’s take a look at the properties that define these alloys.

Material Properties:

• 365 Aluminum:
  • Composition: Primarily composed of aluminum, with silicon (7%) as the primary alloying element.
  • Strength: Exhibits good strength, particularly in applications requiring high-temperature resistance.
  • Finish: Elevated silicon provides a smoother surface finish.
  • Corrosion Resistance: Shows good resistance to corrosion, making it suitable for various environments, including marine applications.
  • Weldability: Welds well using conventional methods, enhancing its versatility in fabrication processes.
• 6061 Aluminum:
  • Composition: Contains magnesium and silicon as its primary alloying elements, with magnesium providing strength and silicon (.6%) aiding in fluidity.
  • Strength: Provides excellent strength-to-weight ratio, making it ideal for structural applications.
  • Machinability: Exhibits good machinability, allowing for easy shaping and finishing of cast parts.
  • Corrosion Resistance: Offers decent corrosion resistance, although not as high as some other aluminum alloys.
  • Weldability: Welds well using various methods, but precautions are necessary to avoid weakening the material.

Case Study:

Our customer sought to compare the performance of 356 and 6061 aluminum alloys for a specific project requiring high strength and optimizing the relationship with a mating material. In the JCT foundry we ran a series of tests, pouring both alloys into identical molds under controlled conditions.

Results:

• Strength: 6061 aluminum exhibited superior strength, meeting the project’s requirements for structural integrity.
• Corrosion Resistance: Both alloys displayed satisfactory corrosion resistance, with 356 aluminum showing slightly better resistance in marine environments.
• Surface Finish: Due to its higher fluidity, 356 aluminum produced parts with smoother surface finishes, reducing the need for post-casting machining.
• Machinability: While both alloys were machinable, 6061 aluminum required less effort during machining processes, saving time and resources.

Conclusion:

In conclusion, our customer identified the surface finish of the casting as the critical requirement of their application. The elevated silicon in the 356 provided the best bond between the cylinder and the mating material. The 6061 casting, while stronger, didn’t react well with the bonded material and affected the customer’s end-product. The choice between 356 and 6061 aluminum alloys for centrifugal casting depends on the specific requirements of the application. While 356 aluminum offers better fluidity and surface finish, 6061 aluminum excels in strength and machinability. In this case, the customer chose 356 for their application. Understanding the unique properties of each alloy is essential for making informed decisions and achieving optimal results in metal casting projects.

For help with a component part project, please access our Request a Quote Form or call 262-377-9440.

Posted by
Isaac Brummer Project Engineer / Estimator
Johnson Centrifugal Technology
ibrummer@jct-usa.com

References:

• ASM International. (2016). ASM Handbook, Volume 15: Casting. ASM International.
• Callister Jr, W. D., & Rethwisch, D. G. (2017). Materials Science and Engineering: An Introduction (9th Edition). Wiley.
• Material Property Data Sheet- JC6061-T6CLE Revision 3 Issued September 21, 2004.
• Exile Machine Works Standard Practice- Alum Casting Alloy- #356 Issued May 29, 1968