Microstructure and properties of a novel Cu-Mg-Ca alloy with high strength and high electrical conductivity

Abstract

The contact wires in high-speed railway industry should have high strength, high electrical conductivity, and high industrial manufacturing feasibility. An economical Cu-0.29Mg-0.21Ca (wt.%) alloy has been designed and synthesized by non-vacuum melting and casting followed by thermal-mechanical treatments. Microstructure evolutions and mechanical properties of the studied alloy were investigated systematically. Microstructure observations showed that after cold deformation, the initial grain size was significantly refined into small grains full of sub-structures with an average size of 400 nm. After homogenized at 780 °C for 1 h, followed by cold rolling reduction of 80%, then annealed at 200 °C for 1 h, properties measurements revealed that the studied alloy had outstanding comprehensive performance with an ultimate tensile strength of 545 MPa, a yield strength of 526 MPa, an elongation of 3.60%, and an electrical conductivity of 71.79%IACS. The high electrical conductivity was due to the addition of Ca which purified the copper matrix through reacting with some impurity elements and caused little electron scattering. The high strength was attributed to the dispersion strengthening, solid solution strengthening, sub-structure strengthening, and dislocation strengthening, in which sub-structure strengthening is dominate.