Abstract
In this paper, the aim was to determine if ASC91 (9 % Al, 1 % Cu) could be replaced with ASC73 (7 % Al, 3 % Cu) aluminium alloy, with presumably improved machinability due to lower silicon content (9 to 7 %) and retained mechanical properties due to a higher copper content (1 to 3 %). The test samples were excised from cylinder heads produced by the lost-foam casting technique in industrial conditions. The tensile properties (proof strength, ultimate tensile strength, elongation and modulus of elasticity), fatigue performance, microstructure and machinability of two as-cast aluminium alloys were examined. The results of the fatigue tests were statistically analyzed using the stair-case method described in the UNI 3964 standard. Tensile properties of the ASC91 were higher, while fatigue properties were higher in the ASC73 alloy. The resultant force was lower for the ASC73, while roughness was lower for the ASC73 alloy, if the feed per tooth is higher than 0.21 mm/t. Two main factors that influence such behaviour are the amount of eutectic silicon and the α-solid solution adhesion to the cutting tool. Keywords: aluminium cast alloys; tensile properties; fatigue; machinability; roughness.
Highlights
The selection of casting alloys for the automotive industry, where aluminium and silicon alloys have a very important role, strongly depends on a number of factors, such as the service requirements and technological factors required to achieve the economy of processing, as stated by Dwivedi et al [1]
ASC91 alloy is has a lower σD if the fatigue limit is set at 10 % and higher σD if fatigue limit is set at 90 %, indicating that ASC91 has a narrower range of σD compared to ASC73, but the 50 % value in ASC91 is slightly lower than that of the ASC73 alloy
The room temperature mechanical properties: modulus of elasticity, proof strength, tensile strength and elongation are all higher in the as-cast ASC91 alloy compared to the as-cast ASC73 alloy
Summary
The selection of casting alloys for the automotive industry, where aluminium and silicon alloys have a very important role, strongly depends on a number of factors, such as the service requirements and technological factors required to achieve the economy of processing, as stated by Dwivedi et al [1]. Typical aluminium casting alloys contain silicon, which may occur as primary silicon particles in hypereutectic alloys (over 12 % of silicon) and as a phase that forms the eutectic (eutectic silicon), as reported by Kamiya et al [3]. Liu and Chou [4] as well as Kamiya et al [3] reported that extremely hard silicon particles contribute to severe tool wear which greatly reduces the tool life. A traditional way of providing an increased machinability (lower cutting forces and surface roughness) is to decrease the silicon content in an alloy. This has an adverse effect on alloy’s mechanical properties. An alternative may be to apply a relatively low silicon content combined with the addition of copper
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
