Interfacial reaction and diffusion kinetics in solid-liquid couples of the Al – Cu – Zn system: experiments and multiscale simulations

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The ability of combining materials with different mechanical, chemical and physical properties in a single component gives rise to the development of hybrid components with improved properties that meet technological and industrial advances. The compound casting process is highlighted here, as it is an efficient method to produce semi-finished hybrids. During the process, the high temperatures promote diffusion and reaction of the starting products at the contact interface and brittle intermetallic layers form. From a technological point of view, engineers seek to understand how the development of intermetallic phases affects the performance of their final component while metallurgists and material scientists contribute the essential information on alloy chemistry responsible for the final bond quality of the hybrid parts. Understanding and controlling the formation and growth of these intermetallic phases is, therefore, the key factor in optimizing the bond strength of newly developed hybrid components. In this matter, being able to reliably predict the final intermetallic layer thickness and to avoid a series of trial-and-error experiments is fundamental. At the moment, for compound casting of aluminium alloys and brass, the numerical prediction of the intermetallic layer thicknesses was hindered due the complex diffusion behavior of the main elements Al, Cu and Zn. The aim of the present project is the development of a sequential multiscale approach, where molecular dynamics (MD) simulation is expected to provide the diffusivity data that are needed to be included into the macro-model equations that describe the solid-liquid diffusion process during compound casting. That multiscale approach will allow the prediction of intermetallic layers thicknesses in the multicomponent-multiphase complex Al-Cu-Zn system. To achieve our goal, fundamental diffusion experiments are essential to validate the MD simulation results. Laboratory scale size solid-liquid diffusion experiments will be performed in order to investigate the interface formation mechanism and to validate the results for the intermetallic layers thickness.