Abstract
The extrusion of Al and an Al–Cu alloy has been investigated using both direct and indirect extrusion modes. The friction conditions obtaining in the two processes are analysed and discussed. The increment ofpressure necessary to cause breakthrough of extrudate is shown to exist in the indirect process, and its magnitude and nature are compared with the direct process. The total pressure requirements for the two processes are analysed and presented as functions of the material constants. It is shown that good surface quality is obtainable more readily by using the indirect route, and equations are presented illustrating the dependence of this feature on the temperature-compensated strain rate. Limit diagrams are presented for 2014 alloy and their interpretation discussed.
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