Al-Based Foams as Permanent Cores in Al Castings: Effect of Surface Skin Thickness and Composition on Infiltration and Core-Shell Bonding

Abstract

An emerging and still poorly explored application of aluminum foams is their potential use as permanent cores (inserts) in the casting of aluminum alloys. In this context, Al-based foams can introduce a weight reduction, the obtainment of cavities, a strength increase, the ability to absorb impact energy and vibration, acoustic insulation ability, the possibility to simplify the technological processes (no removal/recycling of traditional sand cores), and finally, they can be fully recyclable. Cymat-type Al foams with thin outer skin were used as permanent cores in Al-alloy gravity casting in the present research. Al-foams were characterized in terms of porosity, density, cell wall and skin thickness, surface chemical composition and morphology, and compression resistance. Cast objects with foam inserts were characterized by means of optical microscopy. The preservation of up to 50% of the initial porosity was observed for foam inserts with higher density. Metallurgical bonding between the foam core and the cast metal was observed in some regions.

Co‐Casting of Al and Al‐Foams

“…According to these results, co‐casting experiments by the authors, using foam cores with thin outer skin almost free from stable surface oxides, reveal a good bonding. [ 31 ] However, the absence of a thick skin did not prevent infiltration in this case.…”

Homogeneous Age-hardening of Large-sized Al-Sc Foams via Micro-alloying with Zr and Ti

“…Among which, only two methods, namely, melt foaming and powder metallurgy, are industrialized as cost-effective. Nonetheless, the relative low compressive strength of the Al-based foams fabricated by the above two methods, which is usually less than 15 MPa, impedes widespread applications [ 6 , 7 ].…”