Oak Ridge National Laboratory scientists and automakers have developed a new cast aluminum alloy for engine cylinder heads, which could lead to more fuel-efficient internal combustion engines.
The research team involved ORNL researchers and representatives from Fiat Chrysler Automobiles and a cylinder head manufacturer in what Amit Shyam calls a combination of tools and expertise that made the technology possible.
Shyam is a senior research and development staff member in ORNL's alloy behavior and design group.
The problem, in this case, was engine alloys that have not changed in 30 years.
In developing a new alloy, researchers started with a Rolls Royce alloy originally developed for World War II aircraft.
"The thing about this alloy is that it's very expensive and not very castable," Shyam said.
It continues to be used, however, because it can retain its mechanical properties at higher temperatures, which is especially pertinent as automakers push for stronger, more powerful engines.
"The general trend there is to make smaller engines that can have a higher power density," Shyam said.
A common technique for doing that is turbocharging, like Ford's Eco Boost feature, which has been connected to overheating, cracked cylinders and engine fires.
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"They generate more horsepower per unit volume, but as you're doing that, temperatures of various parts of the engine go up and the current alloys are essentially not able to meet them very effectively," Shyam explained.
"There's an industry-wide demand for making alloys that can go to higher temperatures and accommodate these higher-efficiency engines that automakers are designing and developing right now," Shyam said.
The Rolls Royce alloy, modeled on the Titan
The scientists looked at the Rolls Royce alloy with some of the most powerful electron microscopes in the world and modeled the alloy's elements on the laboratory's Titan supercomputer.
"We spent a lot of time trying to understand what makes the Rolls Royce alloy behave the way it does," Shyam said. "By understanding the mechanisms of what makes this alloy so good, we were able to design one that is significantly cheaper and very castable."
The scientists compared how their new alloy performs under residual stress to its World War II-era predecessors using neutron diffraction at the laboratory's powerful Spallation Neutron Source.
“Understanding residual casting stresses of an engine component, particularly in areas of high cyclic stress and temperature, provides opportunities to improve both performance and durability,” said Chris Glaspie of Fiat Chrysler Automobiles, an industry partner for the project.
The resulting product is lighter, more durable and more easily manufactured than engine alloys that came before it. The team has several patent applications under consideration now and the technology won a research and development award last year.
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If it hits the commercial market, the laboratory said, it may help reduce carbon dioxide emissions without sacrificing vehicle performance.
Shyam said the team was not concerned with the Environmental Protection Agency rollbacks of Obama-era requirements on fuel efficiency.
After all, people still want to spend less on gas. Energy Information Administration data suggests Americans spent about $1,400 per year on gas in 2015, about $1,000 less than just one year before that.
"If you can increase the efficiency, you can save a lot of money doing that," Shyam said.
"This is a worldwide trend of providing more power density in an engine and regulations are getting more stringent across the world. Our understanding of our work with our industry partners suggests that this is a trend that is going to continue."