Fiat Chrysler Creates New Aluminum Alloy for Engines

Fiat Chrysler Automobiles (FCA) has created an aluminum alloy that exceeds the limitations of alloys currently used in vehicle engine cylinder heads.

The new alloy, developed by FCA, the Oak Ridge National Laboratory and supplier Nemak, stays strong up to 300°C (572°F). This surpasses, by a wide margin, the limits of existing alloys, which begin to weaken and crack above 200°C (392°F).

The automaker has started replacing six-cylinder engines in some vehicle models with four-cylinder engines, which can match the six-cylinder for power while being more fuel-efficient. In order to keep up with the bigger engine, the four-cylinder engine must generate more pressure and higher compression ratios. This creates more heat in the cylinder head, which can be the hottest part of an engine.

That’s where the new alloy, ACMZ, can make a difference. ACMZ may enable engineers to narrow the “bridge” areas in the cylinder head: the areas of metal between the valves, spark plug and direct fuel injector. Narrowing the bridges can make room for larger valves or even a second spark plug, giving engineers more flexibility in engine design.

ACMZ is different than other alloys because it uses copper rather than silicon as the strengthening component. But copper can be expensive, and the metal tends to crack as it cools.                                                

Oak Ridge’s advanced probes allowed engineers to understand down to the atomic level what happens with an alloy as it cools. The lab’s supercomputer powered a predictive development process, known as integrated computational material engineering, to virtually create 50 new aluminum-copper recipes and simulate how they would handle the cooling process. The team was able to narrow the different recipes down to seven promising alloys, including ACMZ, within 24 months.