Game Changer: New Aluminum Alloys For Turbo Engines
Fiat Chrysler Automobiles (FCA) is changing things up a bit for turbocharged engines. FCA announced on July 2nd that they teamed up with lightweight Original Equipment Manufacturer (OEM) parts supplier Nemak and Tennessee’s Oak Ridge National Laboratory to develop a new aluminum alloy for turbocharged engines.
This improvement comes after FCA was faced with a major challenge due to cylinder heads breaking from the intense heat generated during an engine’s combustion cycle, specifically when higher compression ratios and increased pressure was applied. These two operations produced more power and fuel efficiency, but also a lot of heat! Today, many aluminum heads are created from aluminum alloy grades 319 or 356. Those alloy grades begin to severely decline in integrity once the temperature hits above 200 degrees Celsius (392℉), thus creating that break in the cylinder heads known as “hot tear.”
This new alloy creation, from Oak Ridge National Laboratory in Tennessee and casting supplier Nemak, goes by either 16HT or ACMZ, can handle temperatures up to 300 degrees Celsius (572 ℉). According to FCA, this new alloy may enable engineers to narrow the “bridge” areas in the cylinder head – the areas of metal between the valves, the spark plug, and the direct fuel injector. In order for this to take full effect, the silicon found in some alloys will be replaced with copper – a combination once thought unthinkable due to the potential for copper to crack after the casting application. However, by narrowing that bridge, more space is available for larger valves (possibly even a second spark plug), which allows engineers the room to be flexible when tailoring an engine. The key here is delivering more efficiency without sacrificing performance.
“When we focused on copper, other people in the industry almost laughed us off, saying we’d never be able to cast that…We knew there was competition, including other teams working at Oak Ridge National Labs, but we outperformed everyone on this.” – Gregg Black, senior manager of advanced powertrain engineering at FCA, in a company blog post.
What’s interesting about this new concept is that the alloys can be machined and cast using the same technologies used today, and it only costs 7 percent more than the current alloys. According to FCA, the three-year, $3.5-million project is sponsored by the federal government under a Cooperative Research and Development Agreement known as a CRADA.
Oak Ridge’s laboratory played a vital role in helping engineers understand what happens with an alloy as it cools. Their advanced probes can measure this temperature transition at the atomic level, thus allowing engineers to inspect the formation, size and location of strengthening elements called precipitates. While using a predictive development process known as Integrated Computational Material Engineering (ICME), the Titan (ranked the third most-powerful supercomputer in the US) facilitated the CRADA team to virtually produce 50 never-before proposed aluminum-copper recipes to then simulate the cooling and performance properties. This allowed Nemak and FCA to narrow down the new recipes to just seven options.
“The Titan and ICME let the team focus only on truly promising candidates instead of spending time on trial and error,” Black says. “It’s like Star Wars stuff for us, creating new alloys in the computer without having to pour it.” Black also states, “We’re just getting started on the process to create a design now that we have a material that will work…We feel like we really have a tiger by the tail.”
Unfortunately, consumers still have a few years before a 16HT/ACMZ aluminum head makes its much anticipated debut. Stay tuned…