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Al-high Si alloys are well known for their use as lightweight components in engineering applications, particularly within the automotive industries, due to their high wear resistance and low thermal expansion. It is desirable to increase the hot strength of these alloys by increasing the Si content. In this work, I have concentrated on the use of Al-high Si alloys for land vehicles. The automobile, engine components, the piston engine, four-stroke cycle and Al-high Si alloys in automotive applications will be discussed in this paper.

Rapid solidification processing is a technique used for refining the primary silicon and seems to be the most promising technique for the production of high Si Al-Si alloys (i.e. Si content greater than 17 wt.%). There are number of routes which can be used to produce rapid solidification, including spray methods, weld methods, and chill methods. Of these, melt spinning is the most widely used industrially due to its high cooling rate and the ability to process large volumes of materials. This paper summarizes melt spinning and rapid solidification, highlighting a potential production route for aluminium-high silicon alloys involving melt spinning followed by hot isostatic processing.

Abstract. Aluminum high silicon alloys have concerned many researchers due to their high wear resistance, lightness, high corrosion resistance and low thermal expansion. Casting of high silicon Al-Si alloys (i.e. Si content greater than 17 wt.%) will generate large degrees of segregation and coarse microstructures due to the low rates of solidification. The problems associated with ingot casting of hypereutectic Al-Si alloys (i.e. segregation, coarse microstructures and porosity) may be overcome by rapid solidification processing such as spray, weld, and chill methods (e.g. melt spinning). The alloys under consideration here contain Al, Si, Zr, Cu, Mg, Fe and Ni. These alloys were produced by rapid solidification i.e. melt spinning. The aim of this paper is to characterise the hardness of material produced by rapid solidification at various stages of production. Several alloy variants were examined and relate the hardness to the microstructure. Piston A390 made by casting was examined for comparison.

Aluminium silicon alloys are the most used raw material for automotive applications. One of the main limitations on using aluminium high silicon alloys is the formation of coarse brittle phases under conventional solidification conditions. However, rapid solidification processing (RS) (for example, through melt spinning) is very effective in limiting the coarsening of primary silicon due to the high cooling rate. In the present work, characterisation of the material at the first stage of production as melt-spun ribbon and flake has been carried out. The microstructures show typical characteristics of a ‘featureless zone’ on the wheel-side and coarser microstructures on the air-side, with clusters of silicon particles evident. At high magnification, on the wheel-side, TEM and FEGSEM reveal local variations in the silicon and aluminium content (although on average there is no macrosegregation from the wheel-side to the air-side during solidification). In FEGSEM, the ‘rosette-structure’ also displays local variations in Al, Si, Fe, Cu and Ni over a scale of a few microns.