Effect of Trace Elements on the Thermal Stability and Electrical Conductivity of Pure Copper

Abstract: The impact of introducing trace transition elements on the thermal stability and conductivity of pure copper was examined through metallographic microscopy (OM), transmission electron microscopy (TEM), and electrical conductivity measurements; the interaction between trace transition element and trace impurity element S in the matrix was analyzed. The results show that the addition of trace Ti and trace Cr, Ni, and Ag elements significantly enhances the thermal stability of the pure copper grain size. After high-temperature treatment at 900 °C/30 min, the grain sizes of Cu, Cu-Ti-S, and Cu-Cr-Ni-Ag-S were measured and found to be 200.24 μm, 83.83 μm, and 31.08 μm, respectively, thus establishing a thermal stability ranking of Cu-Cr-Ni-Ag-S > Cu-Ti-S > Cu. Furthermore, the conductivities of pure copper remain high even after the addition of trace transition elements, with recorded values for Cu, Cu-Ti-S, and Cu-Cr-Ni-Ag-S of 100.7% IACS, 100.2% IACS, and 98.5% IACS, respectively. The enhancement of thermal stability is primarily attributed to the pinning effect of the TiS and CrS phases, as well as the solid solution dragging of Ni and Ag elements. Trace Ti and Cr elements can react with S impurities to form a hexagonal-structure TiS phase and monoclinic-structure CrS phase, which are non-coherent with the matrix. Notably, the CrS phase is smaller than the TiS phase. In addition, the precipitation of these compounds also reduces the scattering of free electrons by solute atoms, thereby minimizing their impact on the alloy’s conductivity.