Extrusion of three-layer composite hexagonal clad rods

摘要

Composite clad rods consisting of three different materials are applied extensively as conductors, electrodes and chemical devices. Commercial applications involving low temperature niobium-tin alloy (Nb_3Sn) superconductor rods, which have a pure niobium (Nb) core, a copper-tin (Cu-Sn) alloy outer sleeve and a Nb_3Sn diffusion layer in between, stipulate these conductors as, electrodes that are intended for processing as rods of various shapes. During the extrusion process, non-homogeneous deformation tends to occur because the billet consists of materials with different mechanical properties. In this study, the authors present a numerical simulation model based on the upper-bound theorem to analyze three-layer composite clad rods with a hexagonal cross-section under extrusion. A velocity field is also generated with the assistance of a product's cross-section profile functions. The velocity component in the extrusion axis is expressed as a convex distribution. Analytical results indicate that various process variables such as the semi-die angle, reduction of area, friction condition of the die and combinations of the three constituent materials, prominently influence the extrusion process. Moreover, the extrusion pressure, product dimension-change and the probability of sound extrusion are related closely to the process variables.