Grain refiners as liquid metal foam stabilizers

Abstract

The present work reports on the foaming of liquid aluminium containing TiB₂, TiC or TiAl₃ particles (4-11.5 vol.%) which were prepared in-situ by flux-assisted melting using fluorides. This procedure was in analogy to the production of composites containing grain refining particles. The particle size was kept below 1 μm for TiB₂ and TiC and around 10 μm for TiAl₃. Foams were successfully produced using TiB₂ and TiC particles and thus it could be demonstrated for the first time that metal foams can be stabilised by sub-micrometre particles. The influence on foam stability of alloying with Si and dilution of the melt with pure Al was studied in addition. Microstructural analysis of the foams showed that the particles segregate to the surfaces of cell walls leading to an almost dense coverage, thus helping in stabilising the foams.