The Role of Foaming Agent and Processing Route in the Mechanical Performance of Fabricated Aluminum Foams

摘要

The results of the present study highlight the role of foaming agent and processing route in influencing the contamination of cell wall material by side products, which, in turn, affect the macroscopic mechanical response of closed-cell Al-foams. Several kinds of Al-foams have been produced with pure Al by the Alporas melt process and powder metallurgical technique, all performed either with conventional TiH₂ foaming agent or CaCO₃ as an alternative. Mechanical characteristics of contaminating products induced by processing additives, all of which were presented in one or another kind of Al-foam, have been determined in indentation experiments. Damage behavior of these contaminations affects the micro-mechanism of deformation and favors either plastic buckling or brittle failure of the cell walls. It is justified that there is no discrepancy between experimental values of compressive strengths for Al-foams comprising ductile Al + Al₄Ca eutectic domains and those prescribed by theoretical models for closed-cell structure. However, the presence of low ductile Al + Al₃Ti + Al₄Ca eutectic domains and brittle particles/layers of Al₃Ti, fine CaCO₃/CaO particles, Al₂O₃ oxide network, and, especially, residues of partially reacted TiH₂, results in reducing the compressive strength to values close to or even below those of open-cell foams of the same relative density.