Effect of Ce Addition on Fluidity of Casting Aluminum Alloy A356
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is a widely used casting aluminum alloy in the automotive industry due to its excellent castability, easiness of machining, and good mechanical properties.[1–4] With the increasing demand for vehicle lightweighting, aluminum castings with complex shapes are increasingly needed for better mass efficiency of casting components. The ability for production of complex castings is largely determined by the fluidity of the melt, which is defined by the distance of a molten metal to flow before its termination by solidification.[5,6] The fluidity of casting aluminum alloys can also have significant influence on the mechanical properties. For example, insufficient fluidity of the alloy can result in an incomplete fill or cold shuts in a casting, which are considered as casting defects responsible for degradation of mechanical properties. During a die casting process, lack of fluidity will likely cause sticking between the metal casting and mold. This will lead to difficulty in demolding and hence reduce production efficiency. Therefore, the fluidity of casting aluminum alloys has
GUODONG NIU and JIAN MAO are with the School of Materials Science and Engineering, Sichuan University, Chengdu, 610064, China. Contact e-mail: [email protected] JEFF WANG is with China Science Lab, General Motors Global Research and Development, Shanghai, 201206, China. Manuscript submitted April 9, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS A
been a topic of common interest for metallurgists in recent decades.[5,7–9] The addition of alloying elements is one of the commonly used ways to improve fluidity of casting aluminum alloys. Many researchers have investigated the effect of alloying elements on the fluidity of Al-Si hypoeutectic alloys.[6,10] Sabatino et al.[11] demonstrated that higher amounts of Mg in A356 alloy reduced the fluidity due to the formation of complex eutectic phases. Puparattanapong et al.[12] found that 0.2 wt pct Sc addition significantly increased the fluidity of A356 alloy. However, a further increase of Sc content to 0.4 wt pct caused a slightly lower fluidity, probably due to the formation of a large amount of AlSi2Sc2 intermetallic particles in the Al-AlSi2Sc2 and Al-AlSi2Sc2-Si eutectics. The effect of copper on the fluidity and viscosity of an Al-Mg-Si alloy was also studied, and the results show that viscosity increased with the addition of Cu while the fluidity decreased. Changing in the solidification mode was the major reason for the observed reduction in fluidity due to addition of Cu in this alloy.[6,10] Song et al..[13] investigated the effect of the addition of mixed rare earth elements (La + Yb) on the fluidity of A356.2 and it was found that the 0.6 pct (La + Yb) modified A356.2 alloy had a longer fluidity length (670 mm) than that of standard A356.2 (565 mm), possibly due to the morphology change of a-Al and Al8Si6Mg3Fe (Fe phase) by rare earth modification in the alloy.
Fluidity of cast aluminum alloys can also be improved by refining casting microstructure via various alloying schemes. Dahle et al.[8] researched the effect of grain refi
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