Foaming of Aluminum Alloys Derived From Scrap

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 (0.11wt% for the as-received material, increasing to >0.5wt% 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 (<0.3gcm3), 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.