Precipitation Behavior And Mechanism Of Al-5%Cu Aging Under Electric Field

The microstructure evolution and mechanical properties of alloys depend on the heat-treatment. Thus, it is very important to develop and optimize heat-treatment technology for better mechanical performance microstructure. By means of TEM, SEM and DSC, the microstructure evolution and mechanical properties of Al-5%Cu after DC electric field aging and AC electric field aging were studied. The relationship between microstructure and mechanical properties of Al-5%Cu alloys at different status was analysed, main research contents were presented as followed:(1) The application of an electric field (DC or AC) increases the hardness of the alloy at under-age stage, and for the samples with electric field aging, the peak-age time is shorter than without ones. With the increase of the electric field strength (8kV/cm-50kV/cm), the age hardening rate of alloy increase as well.(2) TEM results showed that electric field (DC or AC) aging promotes the precipitation of θ". According to the HRTEM, we can find that electric field has no significant influence on the growth of θ". The number of0" phase increase with the iprove of electric field strength, which means improve electric field strength contributes to the precipitation of θ". When applying an E=50kV/cm DC electric field during aging, the promoting effect of electric field reach the best.(3) Electric field (DC or AC) can reduce the activation energy of0", which indicates that electric field aging can promote the nucleation of θ".(4) Temperature-time-transition(TTT) curves of Al-5%Cu shows that the initial and final transformation curve of θ" phase in the samples aged under electric field (DC or AC) moves to a lower direction in the time axe, which indicates that electric field promotes the precipitation of θ".(5) The calculation result of TF equation shows that the difference between the free energy of Al-5%Cu solid solution and θ" increased significantly with the increase of electric field stength, which indicates that electric field aging promotes the nucleation ofθ".