A cylinder liner made of a new rapidly solidified powder based aluminum alloy has been developed for high-speed motorcycle engines, which have aluminum cylinder liners inserted in a high-pressure-die-cast cylinder block. The new cylinder liner material has a thermal expansion coefficient 20% lower than that of the block material. With this structure, the cylinder liner could be tightly fastened in the cylinder block so that a high machining accuracy of the cylinder bore could be achieved. The structure also enables one to minimize the cylinder bore distortion and the local heating during engine running due to the uniform distribution of the thermal conductivity.
For the cylinder liner material, a chemical composition of 22∼26% Si, 0.1∼0.3% Cu, 0.05∼0.9% Mg, Al bal. (mass %) was chosen. The limited Cu content was due to its good extruding characteristics. The molten alloy was atomized, followed by the cold isostatic pressing (CIP) and vacuum-sintering. The consolidated billet was hot-extruded into a tube form and heat-treated in the T6 condition. The cast alloy as the cylinder block was JIS ADC10 containing 10 mass % Si. The bore was then machined and plated with a SiC particle-dispersed Ni-P galvanic layer.
The physical and mechanical properties of the new cylinder liner material were compared with conventional cylinder liner materials and the effect of chemical composition and microstructure on cylinder liner characteristics was discussed based on the experimental data.
This type of cylinder liner has been successfully used for series production models in the European market to realize a drastic improvement in performance and oil consumption.