Manufacturing of High Conductivity, High Strength Copper for Rail Gun Application

Nanostructured (NS, grain size (d) <100nm) and ultrafine grained (UFG, d<500nm) metals possess superior mechanical and electrical properties over coarse grained (CG, d≫1μm) metals. The strength of metals like copper (Cu) has been shown to be significantly improved when engineered to have fine and ultrafine grain sizes via processes such as cryomilling, Cold Isostatic Pressing (CIP) and Continuous Equal Channel Angular Pressing (C-ECAP). This study investigates the mechanical and electrical properties of laboratory scale copper (Cu) conductors manufactured through several steps including cryomilling followed by cold isostatic pressing and finally C-ECAP and how its strength is affected by a variety of parameters when tested in uniaxial tension. The copper material is fabricated through cryomilling, cold isostatic pressing and (C-ECAP). Mechanical characterization is conducted using uniaxial tensile tests, nanoindentation and hardness tests. Pre and Post fabrication examination of the material with 3D-xray tomography, optical and electron microscope were conducted to gain deeper understanding of the effects of the processing parameters on the material during fabrication and the evolution of the microstructure as the powders go through the manufacturing process. Electrical testing is conducted to evaluate the electrical conductivity of the manufactured copper. While the material showed improved strength and hardness compared to conventional copper material at room temperature, its ductility decreased. Also, higher ECAP temperatures produced materials with higher electrical and mechanical properties.