Novel high-temperature alloys enable lighter, more fuel-efficient truck engines

Lightweight, higher-temperature alloys developed by researchers at the Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL) and funded by DOE's Transportation Technologies Office (TTO) have met the strength and durability operating requirements of General Motors' (GM) new low-mass, high-efficiency (LMHE) medium-duty truck engine. This achievement enables lighter truck engines that improve fuel efficiency and performance without sacrificing strength or durability.

Under a cooperative research and development agreement, ORNL tested two aluminum alloys - cast ACMZ (AlCuMnZr) and printed DuAlumin3D - in a prototype GM engine. The materials enabled a more-than-10-percent improvement in fuel efficiency and a 15-percent reduction in weight. Commercial engines in trucks, such as GM's Chevrolet Silverado 3500, have to withstand heavy loads and prolonged use.

However, metals tough enough to meet these requirements are typically dense, which reduces fuel efficiency. Lighter materials can improve gas mileage, but most commercially available lightweight metals struggle to endure higher temperatures and pressures in high-performance engines, which can result in premature failure. The ORNL-developed alloys overcome this tradeoff by delivering both high-temperature durability and reduced weight.

ORNL's ACMZ was used to cast the LMHE's cylinder heads and engine block. ACMZ is a high-strength, affordable aluminum alloy designed to handle intense heat and stress. DuAlumin3D, which was designed for high-performance pistons, is a novel 3D-printable alloy that combines lightweight design with the best-known combination of strength and durability at extreme temperatures for a structural aluminum alloy.

"The shared goal between ORNL and GM was to demonstrate next-generation engines for high-volume trucks that are lighter, lower-cost, and more efficient, all without sacrificing power and performance," said Allen Haynes, director of the ORNL-led TTO Powertrain Materials Core Program consortium.

These two alloys, along with advanced combustion and other materials and manufacturing technologies, enabled the GM LMHE engine to pass rigorous performance and durability tests, advancing materials science that supports the nation's automotive and manufacturing sectors.

"This is a remarkable set of combined outcomes by the GM design team," said ORNL's Amit Shyam, who leads the Alloy Behavior and Design Group. "Any weight shaved off an engine equates to more miles per gallon for the average driver, saving not only energy, but money."

For their multi-organization efforts, the GM-led team, including ORNL and several suppliers, earned a prestigious 2025 R&D 100 Award and a DOE 2025 Team Award for demonstrating real-world potential to deliver fuel- and cost-efficient lightweight engine technologies to the domestic market. This recognition builds upon a history of accolades for the ORNL alloy development team - both ACMZ and DuAlumin3D previously received R&D 100 Awards in 2017 and 2022 for breakthroughs in high-temperature, high-performance, lightweight metals.

"We are very pleased to receive this recognition," Shyam said. "It's a proud moment for our team, and it highlights how our National Labs are uniquely positioned to rapidly develop the next generation of lightweight material innovations to help drive the future competitiveness of U.S. manufacturing."

This project integrated materials science, advanced manufacturing, combustion engineering, and computational modeling expertise into an impactful research cooperative between U.S. industry and a National Laboratory. The accelerated alloy design methodology developed by ORNL allows researchers to move from a targeted new material concept to real-world prototype applications in 2 to 4 years, as compared to the 10 to 15 years that have been historically required. This novel approach significantly reduces the time, costs, and risks of bridging the gap between laboratory breakthroughs and commercial products.

Shyam's lightweight alloy team received support from Alex Plotkowski and Allen Haynes. TTO supported the cast ACMZ alloy, and TTO and DOE's Advanced Materials and Manufacturing Technologies Office jointly developed the printable DuAlumin3D alloy.

"Beyond the lab, the effort was part of a broader collaboration led by GM, with participation from universities and suppliers across the country," Shyam said. "It proves that materials science is not just groundbreaking, but also road ready."

UT-Battelle manages ORNL for DOE's Office of Science, the single largest supporter of basic research in the physical sciences in the United States. The Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit energy.gov/science. - Julya Johnson