Foaming of Aluminum Alloys Derived From Scrap

Abstract Aluminum alloys made from machining chips that have been heat treated and re‐melted, have been successfully foamed (after the addition of TiH₂) using processes analogous to both the “Alporas” and “Formgrip” methods. The high oxygen contents associated with the swarf (0.11 wt% for the as‐received material, increasing to >0.5 wt% after conditioning) results in large fractions of both clustered and dispersed oxide films in the melt. It is these films that enhance the “foamability” of this material. Through additional alloying with Mg and holding in the liquid state to allow reaction to take place, fragmentation and wetting of the oxides occurs and foams with low densities (<0.3 g cm⁻³), good pore structures, and good stability were obtained. The use of scrap material, without costly or embrittling additives, offers a low cost route to the manufacture of high quality foams.