Investigation on the Interface Characteristics of Al/Mg Bimetallic Castings Processed by Lost Foam Casting
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INTRODUCTION
ALUMINUM and magnesium alloys are regarded as the most important engineering materials in automotive and aerospace industries because of their many advantages including low density, high strength-to-weight ratio, and excellent castability.[1–4] However, one of these materials alone does not satisfy the requirements of lightweight constructions in many cases, for instance, magnesium alloy suffers from low ductility, creep resistance, and high-temperature strength, while aluminum alloy can satisfy these, particularly in the automotive industry.[5–7] Using combined structures consisting of aluminum and magnesium alloys as the bimetallic materials may be the most effective way to meet the demands for engineering applications because they combine several promising properties that cannot be provided by monolithic materials.[8]
WENMING JIANG, Associate Professor, is with the State Key Lab of Materials Processing and Die and Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, P.R. China, and also with the School of Mechanical & Electrical Engineering, Wuhan Institute of Technology. ZITIAN FAN, Professor, and GUANGYU LI, LONG WANG and FUCHU LIU, Graduate Students, are with the State Key Lab of Materials Processing and Die and Mould Technology, Huazhong University of Science and Technology. Contact e-mail: [email protected] Manuscript submitted August 8, 2015. Article published online February 24, 2016 2462—VOLUME 47A, MAY 2016
The LFC process is a cost-effective and environment-friendly near-net-shape casting technology without the need for cores,[9–11] and suitable for manufacturing complicated aluminum and magnesium alloys’ precision castings.[12,13] First, the foam pattern based on the part shape is prepared. Subsequently, the prepared foam pattern is coated with the refractory slurry and then placed inside a sand flask. After modeling and vibration compacting, the molten metal is poured directly into the foam pattern, thereby decomposing the foam pattern as gas and liquid products. As a consequence, the molten metal replaces the foam pattern and duplicates all features of the foam pattern.[14] Currently, an interesting advantage of the LFC process is the possibility of mounting the desired solid part inside the foam pattern and then performing the pouring process, which will be an attractive method to prepare the bimetallic castings because it has numerous advantages, such as low cost, no cores, tight tolerance, complex geometries, and smooth as-cast surface. A number of researchers have carried out such tries. Hejazi et al.[15] investigated the effect of copper insert on the microstructure of gray iron produced via LFC process. Divandari et al.[16] reported the study of Al/Cu rich phases formed in A356 alloy by inserting Cu wire in pattern in LFC process. Choe et al.[17] studied the interface between steel insert and aluminum casting in LFC process. There are many methods to fabricate Al/Mg bimetallic materials, for example, compound casting based on sand casting,[18] friction sti
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