Influence of Rare Earth Element La on the Performance of Copper-Based Composites

Copper-based composites with La contents of 0.02 wt.%, 0.04 wt.%, 0.06 wt.%, and 0.08 wt.% are prepared by spark plasma sintering using the rare earth element La and electrolytic Cu powder as raw materials. The influence of the La mass fraction on the properties of Cu-La relative to copper-based composites are explored by observing the microstructure and testing the density, hardness, and electrical conductivity. The results show that after La is added to Cu via spark plasma sintering, the originally arbitrarily oriented grains in pure copper are gradually adjusted to a preferred orientation. When 0.04 wt.% La is added, the degree of preferred orientation in the copper-based composites increases. The strengthening mechanisms of La for copper-based composites are grain refinement strengthening, dispersion strengthening, solid solution strengthening and second phase strengthening. With increasing La addition, the hardness values of the copper-based composites increase: from 45.4 HV to 57 HV, and the tensile strength up to 215 MPa. When 0.04 wt.% is added, the conductivity reaches the highest value of 88.2 IACS%. However, the addition of excessive La leads to excessive formation of the Cu6-La phase, which leads to an increase in the mechanical properties of copper-based composites but a decrease in the conductivity.