Tensile and fatigue properties, machinability and machined surface roughness of Al-Si-Cu alloys

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.