Abstract
This paper aims to assess the role of Cu on Al-Si-Mg alloys, in a range of 0 - 5 wt%, qualitatively on microstructure, defect formation, in terms of porosity, and strength in the as-cast conditions. The ternary system of Al-Si-Mg, using the A356 alloy as a base material, were cast using the gradient solidification technique; applying three different solidification rates to produce directional solidified samples with a variety of microstructure coarsenesses. Microstructural observations reveal that as the Cu levels in the alloys are increased, the amounts of intermetallic compounds as well as the Cu concentration in the α-Al matrix are increased. Furthermore, the level of porosity is unaffected and the tensile strength is improved at the expense of ductility.
Highlights
The alloy and cooling conditions govern to a large extent the mechanical properties of Al-Si cast alloys
This paper aims to assess the role of Cu on Al-Si-Mg alloys, in a range of 0 - 5 wt%, qualitatively on microstructure, defect formation, in terms of porosity, and strength in the as-cast conditions
The cooling rate determines the coarseness of the microstructure including the Secondary Dendrite Arm Spacing, SDAS, which is often used as measure of the coarseness of the microstructure, the fraction, size and distribution of intermetallic phases and the segregation profiles of solute in the α-Al phase
Summary
The alloy and cooling conditions govern to a large extent the mechanical properties of Al-Si cast alloys. The strength of components is governed by proper additions of Cu and Mg, which will be done at the expense of ductility [1,2]. The plastic deformation behaviour will be depending upon factors such as whether the Cu and Mg are found as coarse intermetallic compounds, the level of Cu and Mg in solid solution, or if Cu and Mg are found as GP zones formed at room temperature and/or as precipitates due to a post solidification treatment. Cu and Mg present in Al-Si cast alloys lead to the formation of bands of coarse Si particles as they enlarge the solidification interval, leading to an increased risk in forming shrinkage porosity, leading to premature failures [3]
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