Aluminum Foams as Permanent Cores in Casting

Sara Ferraris,Graziano Ubertalli,Antonio Barbato,Antonio Santostefano

doi:10.3390/iec2m-09253

Sara Ferraris, Graziano Ubertalli + Show 2 more

Open Access

https://doi.org/10.3390/iec2m-09253

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Publication Date: Feb 20, 2021
Citations: 1	License type: CC BY 4.0

Affiliation: Polytechnic University of Turin

Abstract

Their low density and high specific stiffness and impact energy/vibration absorption ability make Al-based metal foams promising materials in applications for which a light weight and energy/vibration absorption abilities are crucial. In view of these properties, Al-based foams can be extremely interesting as cores in cast components in order to improve their performances and simplify their whole technological process. However, both in the scientific literature and in technological application, this topic is still poorly explored. In the present work, Al-based metal foams (Cymat foams and Havel metal foams in the form of rectangular bars) are used in a gravity casting experiment of an Al-Si-Cu-Mg alloy (EN AB-46400). The foams were fully characterized before and after insertion in casting. Porosity, cell wall and external skin thickness, microstructure, infiltration degree, and the quality of the interface between the foam core and the dense cast shell, have been investigated by means of optical microscopy and scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS). The analyses evidenced that a continuous and thick external skin protect the foam from infiltration by molten metal, preserving the initial porosity and insert shape. A detailed analysis of the foam’s external skin highlights that the composition of this external skin is crucial for the obtaining of a good joining between the molten metal and the Al foam core. In fact, the presence of Mg oxides on the foam surface prevents bonding, and maintains a gap between the core and the shell. This point opens up the opportunity to design innovative surface modifications for this external skin as promising strategies for the optimization of cast components with a foam core.

Highlights

Al-based foams are gaining increasing interest due to their low density, high specific stiffness and impact energy/vibration absorption ability, fire resistance, and recyclability [1,2]
The use of Al-based foams as cores in casting component production is still poorly explored, even if it can offer numerous advantages, such as weight reduction compared to dense components, the obtainment of cavities in cast objects, strength increase in terms of hollow or T-shaped sections, impact energy and vibration absorption, acoustic insulation, and the simplification of the technological processes and recyclability [3]
Al-based foams in the form of bars have been used as cores in gravity casting experiments

Summary

Introduction

Al-based foams are gaining increasing interest due to their low density, high specific stiffness and impact energy/vibration absorption ability, fire resistance, and recyclability [1,2]. The use of Al-based foams as cores in casting component production is still poorly explored (just a few papers/year, less than 10 patents published on this topic), even if it can offer numerous advantages, such as weight reduction compared to dense components, the obtainment of cavities in cast objects, strength increase in terms of hollow or T-shaped sections, impact energy and vibration absorption, acoustic insulation, and the simplification of the technological processes (no removal/recycling of traditional sand cores) and recyclability [3]. The few published works related to the use of Al-based foams as cores in casting include some details and characterizations, but almost no solutions have been proposed and discussed to overcome the criticisms. The present research considers and compares different foams, analyzes both foams and cast objects, establishes the main issues, and proposes new strategies for their overcoming

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Conclusion