Effect of cerium on microstructure, texture and properties of ultrahigh-purity copper

The effects of Ce addition (310 ppm and 1500 ppm) on the microstructure, texture and properties of ultrahigh-purity copper (99.99999%) were systematically studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD) analyses, combined with the microhardness and conductivity tests. Regarding the microstructure of the as-cast and as-extruded samples, the addition of Ce refines the grain size of the ultrahigh-purity copper and the refinement effect of 310Ce alloy is greater than that of 1500Ce alloy. This is due to the stronger component supercooling and the accelerated recrystallization caused by lower Ce content. In addition, Ce can react with Cu to form the Cu–Ce eutectic phases, which are deformable during the hot deformation. Furthermore, the added Ce can weaken the texture, showing a variation of brass recrystallization (BR), rotated cube, copper and S texture components, which depends on the recrystallization, the particle stimulated nucleation (PSN) as well as the stacking fault energy (SFE). Most remarkably, the introduction of Ce enhances the hardness of the ultrahigh-purity copper without obviously reducing its conductivity. The major {111} orientations and the stress distributions are responsible for such a superior conductivity of the Ce-containing alloys.