Abstract
Al and Mg alloys are main lightweight alloys of research interest and they both have superb material properties, i.e., low density and high specific strength, etc. Being different from Al alloys, the corrosion of Mg alloys is much more difficult to control. Therefore to combine merits of these two lightweight alloys as a composite-like structure is an ideal solution through using Al alloys as a protective layer for Mg alloys. Compound casting is a realistic technique to manufacture such a bi-metal structure. In this study, a compound casting technique is employed to fabricate bi-layered samples using Al and Mg and then the samples are analysed using electron probe micro-analyzer (EPMA) to determine diffusion behaviours between Al and Mg. The diffusion mechanism and behaviours between Al and Mg are studied numerically at atomic scale using molecular dynamics (MD) and parametric studies are conducted to find out influences of ambient temperature and pressure on the diffusion behaviours between Al and Mg. The results obtained clearly show the effectiveness of the compound casting process to increase the diffusion between Al and Mg and thus create the Al-base protection layer for Mg.
Highlights
Magnesium, aluminium and their alloys are the main members of light metals
These two figures show that Al/Mg interface migrates toward the Al-solid phase, and provides evidence which the diffusion coefficient is much greater for Mg-liquid phase than for the Al-solid phase, which have agreement with those results of an Al/Cu system.[6]
In most research the metals were at solid state, there is a lack of study about solid-liquid of Al-Mg system and in this study the solid-Al and liquid-Mg in compound casting process have been developed and studied experimentally and numerically, including molecular dynamics simulation and classic diffusion theory as well as electron probe micro-analyser (EPMA) experiments
Summary
Aluminium and their alloys are the main members of light metals. Magnesium and its alloys are good candidate materials for advanced engineering applications, i.e. automobile and aerospace industries due to their significant advantages of low density, high specific strength and high stiffness.[1,2,3] they have their own weaknesses, such as lower strength at elevated temperatures and poor wear and corrosion resistance, which have made hurdles for their further applications in engineering fields. Semi-finished parts with complex structures, by casting a metal onto or around a solid shape and many researchers have used this process to join similar and dissimilar metallic couple such as Al/cast iron,[5] Al/Cu,[6] mild steel/Mg-Mn,[7] Al/Al,[8] Mg/Mg9 and Al/Mg10 In these papers, the main content is to study the growth of intermetallic,[5] the distribution of interface 6 and the diffusion rate of different elements[7]. Based on the experimental setups, MD simulations are employed to investigate diffusion behaviours in a typical Al-Mg compound casting process at atomic scale with focusing on interfacial interaction between Al and Mg. The classic diffusion theory is utilised to obtain the analytic results on diffusion zone.
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