Powder metallurgy aluminium alloys : characteristics of an Al-Cr-Fe rapidly solidified alloy

An Al-4Cr-1Fe alloy has been evolved utilizing the advantages of rapid solidification technology. The paper describes the formation of the as- atomized (inert gas) powder microstructure and its decomposition during in situ heating. It was observed that the most typical powder microstructure had a cellular morphology with a fine intercellular network consisting of iron-rich phases. Decomposition of the powder during in situ heating commenced from the intercellular network, finally resulting in a matrix with a high volume fraction of chromium-rich globular-like precipitates. Consolidation was achieved through cold compaction and hot extrusion, the alloy being easily extrudable. The room-temperature mechanical properties of the alloy were also assessed. The 0.2 percent proof stress and the tensile strength were below the target limits for dispersion-strengthened alloys, but the elongation and fracture toughness values were very promising. Finally, the extruded microstructure was related to mechanical properties. (Author)