The automotive industry is seriously concerned with emission level control, vehicle weight reduction and recycling. These are the purposes of introducing the all aluminium cylinder block for the combustion engine. The spray forming process led to the fabrication of cylinder liners of high silicon aluminium alloys,also called DISPAL Aluminum alloys in German.
Some aluminum silicon alloys possess characteristics such as good wear resistance combined withlow coefficient of thermal expansion. These alloys have also a high strength weight ratio. Due to these properties, such alloys have been used in several applications in the automotive,aerospace and electric industries . Recent engineering efforts towards improving the physicaland mechanical properties have focused on chemical composition modifications with the objective of improving mechanical strength, wear resistance, ductility and toughness properties of suchalloys. This led to hypereutectic compositions that present low coefficient of thermal expansion andexcellent wear resistance. The outstanding wear resistance is due to the high volumetric fraction offine primary silicon phase and intermetallics. Applications of the AlSi alloys in the automotive industry, include engine blocks and parts of engines, particularly, cylinder liners. The main advantages of the use of these alloys are weight reductions, less emission of gases and low fuel consumption.
Hypereutectic alloys can be produced by ingot metallurgy or by rapid solidification processes, such as: melt spinning, atomisation and spray forming. The use of ingotmetallurgy for the production of these alloys is limited by the range chemical compositions possible. That can be attributed to the formation of eutectic phases and coarse primary siliconphase, due to the low cooling rates associated to the ingot metallurgy. The distribution of coarsesilicon particles in the alloy leads to low ductility and limited workability of the hypereutectic Al-Si alloys produced by ingot metallurgy.