Influence of particulate reinforcements on 6061 materials in extrusion modeling

The comparative extrudabilities of 6061 alloy, 10% Al2O3/6061 and 20% Al2O3/6061 were estimated by finite element methods with DEFORM(TM) software. The direct axisymmetric extrusion was modeled with a square die and sticking friction in tooling that was rigid and preheated. The materials were treated as rigid-plastic with dependence of flow stress on temperature and strain rate determined by torsion testing at 300-500 degreesC and 0.01-5 s(-1). The extrusion ratio, billet temperature and ram speed were varied to study their effects on the load-stroke diagram and find equivalent conditions for alloy and composites. In addition the distribution of velocities, strain, strain rate, temperature and mean stress were calculated and compared to physical simulation; the dependencies of their maximum values on the control parameters were examined. The distributions of the internal variables permit estimation of surface cracking and of extrudate microstructure. Comparison is made with modeling results from other materials. (C) 2003 Published by Elsevier B.V.