A well-established cylinder bore liner material for aluminum engine blocks is Silitec™ (Dispal S260). This spray-compacted, hypereutectic aluminum-silicon alloy is cast into aluminum cylinder blocks using the high pressure die casting (HPDC) process. Silitec™ is well suited to the HPDC process because the thermal energy of the molten aluminum is removed rapidly through the metal die.
Other casting processes such as sand, semi-permanent mold and low pressure die casting have longer solidification times, resulting in additional thermal energy being transferred to the aluminum liners. This additional energy may result in localized melting and deformation of the liner. Thus, in order to use aluminum cylinder liners in casting processes other than HPDC, it becomes necessary to develop alloys that are more resistant to residual heat in the casting process.
In addition to thermal improvement for manufacturability, engine manufacturers also need increased mechanical properties to withstand the increasing combustion pressures of newer engine designs. These higher engine pressures increase the stress on the liner, requiring alloys with higher strength and stiffness.
This paper will describe recent work at PEAK Werkstoff GmbH in Velbert, Germany, to develop new aluminum alloys to meet the needs of different casting processes and higher engine output. Included will be properties of the newly-developed Dispal alloys and recommendations for their application.