The pistons are made with a hypereutectic alloy
and designed with a thick crown area and use a special ring pack so that the boost pressure and heat generated by the turbo system can be handled.
This hypereutectic alloy
became popular in the mid-century for engine cylinder blocks and has remained so due to its wear resistance, low thermal expansion and good elevated temperature service.
Comparing the results of the fluidity and impact strength tests, the study found that a hypereutectic alloy
containing more than 11% dendrite to ensure good impact strength should contain at least 6.
At Porsche, a linerless V-8 block of a hypereutectic alloy
is cast by low-pressure permanent molding.
Just as phosphorus (P) refines primary Si in hypereutectic alloys
, Al-P serves as a nucleant for the eutectic Si in hypoeutectic melts.
3] and SiC inclusions in hypoeutectic Al-Si alloys nucleate pores, while in hypereutectic alloys
the particle is engulfed in the primary silicon phase.