Heat-resistant aluminum alloy for energy-efficient transportation

Summary

A new high-temperature, 3D-printable aluminum alloy, developed by ORNL in less than three years rather than decades, redefines standards for high-performance automotive and aerospace components by offering performance improvements capable of saving billions in fuel costs.

Problem

Materials often set the performance limits for technologies used in harsh environments, such as jet and car engines. Engineers are often faced with a tough choice: either accept lower performance and energy efficiency, or use heavy, costly alloys made from titanium, steel, nickel, or cobalt to over-engineer key parts.

Parts made from conventional aluminum alloys are typically lightweight and low-cost, but unsuitable for high-temperature environments.

Additive manufacturing (AM) can increase performance by enabling complex designs, superior material properties, and more energy-efficient processes. However, less than one half of one percent of the thousands of alloys available through conventional manufacturing methods are suitable for AM.

There is a need for new aluminum alloys for AM that maintain high strength at elevated temperatures, but progress is held back by the slow pace of alloy development—a process that has traditionally taken 10 to 20 years.

Scientific challenge

Conventional high-strength aluminum alloys are unsuitable for AM because they tend to crack as they cool down during AM processing, a behavior known as “hot cracking.” While chemistry modifications can make some of these alloys processable, they still lack the necessary high-temperature integrity (250–400°C) to compete with titanium alloys used in aerospace and automotive applications.

Innovation

A team at the US Department of Energy’s Manufacturing Demonstration Facility at Oak Ridge National Laboratory designed DuAlumin-3D — a printable aluminum-based alloy containing cerium, nickel, and zirconium — for high-temperature applications. DuAlumin-3D is resistant to process defects and has a high fraction of heat-resistant, strengthening particles that form at the nanoscale during printing. These characteristics make the alloy suitable for printing complex geometries such as heat exchangers and pistons. Critically, the alloy also maintains desired mechanical properties up to 400°C.

It took less than three years to progress from conceptualizing DuAlumin-3D to printing full-scale prototype automotive pistons.

A suite of ORNL’s unique combination of materials science capabilities, including rapid X-ray computed tomography, advanced electron microcopy, mechanical testing, computational thermodynamics, and in situ neutron diffraction were used to accelerate the alloy design process. This modern approach to alloy design can also be generalized for accelerated research into other alloys for AM.