Studies on wire hot extrusion processes of metals and metal/CNT

Wire hot extrusion was investigated to produce thin wires of metals and metallic matrix nanocomposites, including aluminum (Al), copper (Cu), and copper/carbon nanotube composites (Cu/CNT, 1%wt). A new energy-based analytical solution was developed to predict extrusion force, where friction effect between die and sample was considered. This analytical solution achieved a much better result than the classical slip line theory and other existing analytical solutions, where friction effect was usually not considered. Finite element (FE) models using ALE method were built to validate the analytical solution under different extrusion conditions. A series of FE simulations were run for different die angles (30°, 45°, and 60°) and two different area extrusion ratios (4:1 and 16:1). The comparison results showed a very good correlation between the analytical solution and FE results. Four wire extrusion tests of metals and Cu/CNT composite were conducted under elevated temperatures (about 300 to 700 ℃). Test results further proved the excellent accuracy of the analytical solution and the necessity of considering friction effect. Trade-off between high temperature oxidation and material fracture during wire extrusion for less ductile materials was also briefly discussed.