Effect of severe plastic deformation via co-extrusion on microstructure and electrical conductivity of copper clad aluminum conductors for e-motor applications

A square-shaped cross-section copper-clad aluminum (CCA) conductor was produced through co-extrusion at room temperature with an equivalent strain of 1.5. The bimetallic conductor retained a high electrical conductivity (EC) of 69.10% International Annealed Copper Standard (IACS), which was owed to aluminum's minor decrease in EC. Super elongated grain channels along the conductor's length were developed from extrusion while a subgrain structure with a low density of dislocations was observed within the elongated grains. Both the elongated grain boundaries and subgrain structure had a minor impact on EC based on both the measured results and analytical calculations. The severely cold-worked copper microstructure which contained heavy dislocation entanglement, lead to a significant decrease in EC. The observed microstructure showed an accumulation of geometrically necessary dislocations attributed to its low stacking fault energy.