Homogenizing treatment and diffusion kinetics of AZ80A magnesium alloy

The microstructure,distribution of elements and phases evolution of as-cast AZ80A magnesium alloy before and after homogenizing treatment were studied by thermal analyzer,optical microscope,X-ray diffraction and scanning electron microscope,etc.The effects of homogenization temperature and time on the structure of the AZ80A alloy were analyzed.Based on the vacancy diffusion mechanism,the spreading activation energy of alloying elements and kinetic equations during the homogenizing treatment were also investigated.The results show that serious dendrite segregation exists in the AZ80A cast alloy,and a large number of continuous eutectic phases of β-Mg17Al12 are observed at grain boundaries;both increasing homogeni-zation temperature and holding time are beneficial for the non-equilibrium eutectic phases to dissolve and alloying elements to diffuse;the alloy is over-burnt when the temperature reached 430 ℃.It is concluded that the proper homogenizing parameters of AZ80A magnesium alloy is 410 ℃ for 25 h and the spreading activation energy is 121.7 KJ/mol,which are in good agreement with the experiment results of the present paper.