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

Resumo

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.