Oak Ridge National Laboratory researchers have additively manufactured (3D-printed) a lightweight aluminum alloy and demonstrated its ability to resist creep or deformation at 300 ˚Celsius.

Materials that can perform under high pressure, high temperature environments are needed for automotive, aerospace, defense and space applications. The alloy, which combines aluminum with cerium and other metals, was printed using a laser powder bed system that deposits one thin layer of material at a time for precise results. Researchers printed pistons made of the alloy for deployment inside of a full-scale engine.

ORNL researchers used a laser power bed manufacturing technique to 3D print a lightweight aluminum and cerium-based alloy that can withstand temperatures up to 300 ˚C, proving high strength and durability for automotive, aerospace and defense applications. Credit: ORNL, US Dept. of Energy

Using powder-bed 3D printing allowed the alloy to rapidly solidify into fine, stable strengthening particles in the microstructure, resulting in the remarkable high-temp creep resistance we measured. We expected notable improvements, but were surprised by how strong and stable these alloys proved to be.

—ORNL’s Ryan Dehoff

In an open-access paper published earlier this year in Scientific Reports exploring the microstructure and properties of additively manufactured Al–Ce–Mg alloys, Dr. Dehoff and his co-authors provide background:

Additive manufacturing (AM) allows for geometric flexibility in part production and offers an increased design space, enabling complex cooling channels, mesh geometries, and sophisticated near net shape parts that are impossible to produce with conventional manufacturing techniques. Specifically, in aluminum alloys, the use of AM could allow for the light-weighting of structural components in aerospace and automotive applications. However, conventional high-strength wrought aluminum alloys are poorly suited for the complex thermal cycles found in AM due to their propensity for solidification cracking.

For example, AM of alloy compositions similar to 7075 and 2024 showed significant processing limitations due to solidification cracking. While solidification cracking can be mitigated through careful processing parameter design in simple parts (e.g., cubes) optimized parameters do not necessarily translate to complex parts.

The difficulties in processing of traditional alloys has led the aluminum additive community to widely adopt near-eutectic Al-Si, more specifically the Al–10Si–Mg alloy. These alloys exhibit excellent castability and resistance to solidification cracking, but show much lower strength than conventional wrought alloys, and poor strength retention at elevated temperatures.

… These challenges in AM processing of conventional wrought Al alloys, and the limited performance of Al–Si alloys, has prompted the examination of new Al alloys specifically designed for AM. Among these, the Al–Ce system is particularly interesting due to its thermal stability and resistance to solidification cracking in castings.

—Sisco et al.

The pistons will undergo additional testing inside of a four-cylinder, turbocharged engine.

Resources

• Sisco, K., Plotkowski, A., Yang, Y. et al. (2021) “Microstructure and properties of additively manufactured Al–Ce–Mg alloys.” Sci Rep 11, 6953 doi: 10.1038/s41598-021-86370-4