Extrusion of Al-Si-X Alloys Prepared from Rapidly Solidified Powders

摘要

Research to provide elemental and practical knowledge of extrusion as guide tobetter understanding of the process as applied to Powder Metallurgy (PM) Al-Si-X alloys is presented. Focus is on the extrusion of two newly designed AlSi alloys both produced by means of air atomization without covering peripheral areas: Al-20Si-3Cu-1Mg and Al-20Si-7.5Ni-3Cu-1Mg. A description of extrusion as a thermally activated process and the influences of extrusion variables on pressure requirement and the friction at the mutual sliding interface (between billet and container) is given. The underlying mechanisms determining the mechanical behavior of the second PM alloy above, which involves the complicated superposition of several strengthening mechanisms, including internal boundary (grain, subgrain and original powder particle boundaries), solid solution, precipitation and dispersion strengthening, are discussed.