Effect of Zr additions and annealing temperature on electrical conductivity and hardness of hot rolled Al sheets

The influence of annealing cycles up to 650 degrees C on the specific conductivity and hardness (HV) of hot-rolled sheets of Al alloys containing up to 0.5% Zr (mass fraction) was studied. Using analytical calculations of phase composition and experimental methods (scanning electron microscopy, transmission electron microscopy, electron microprobe analysis, etc), it is demonstrated that the conductivity depends on the content of Zr in the Al solid solution which is the minimum after holding at 450 degrees C for 3 h. On the other hand, the hardness of the alloy is mainly caused by the amount of nanoparticles of the L1(2) (Al3Zr) phase that defines the retention of strain hardening. It is shown that the best combination of electrical conductivity and hardness values can be reached within an acceptable holding time at the temperature about 450 degrees C.