Effects of rare earth elements on annealing characteristics of Cu-6 wt.% Fe composites

The filamentary composites of Cu-6 wt.% Fe, Cu-6 wt.% Fe-0.05 wt.% RE and Cu-6 wt.% Fe-0.3 wt.% RE were prepared by casting, cold drawing and intermediate heat treatments. The microstructure was observed and the ultimate tensile strength, vickers hardness and electrical conductivity were determined for the composites annealed at different temperatures. The results show that (0.05-0.30) wt.% rare earth elements in Cu-6 wt.% Fe can refine the as-cast microstructure and facilitate the precipitation of secondary Fe particles in the Cu matrix. The filamentary structure of Cu-6 wt.% Fe-0.30 wt.% RE seems to have a higher recrystallized resistance than that of Cu-6 wt.% Fe. With the increase in annealing temperature, the strength and hardness of the composites decrease but the conductivity increases. In particular, there appears a remarkable change of the strength, hardness and conductivity with the annealing temperature over 400 deg. C. The rare earth elements increase the conductivity of the Cu-6 wt.% Fe composites annealed at different temperatures. The improvement in conductivity from the rare earth elements is more significant for the composites annealed at higher than 400 deg. C.