Softening behavior of Al-Zn-Mg alloys with different strengthening mechanisms in a coupled field

The softening behavior of Al-Zn-Mg alloys in solid solutions and aging states was investigated under an electric pulse by establishing the Hall-Fetch relationship. Because intragranular strengthening and grain boundary strengthening are described separately by the Hall-Fetch relationship, the difference between the intragranular softening behavior and grain boundary softening behavior under an electric pulse could be discerned. The effect of an electric pulse on the metal was studied, and it was concluded that this effect was caused by the coupled effect of Joule heating and drifting electrons. The decrease in stress (intragranular and grain boundary) caused by Joule heating was significantly greater for the solid solution alloy than that for the aging alloy. On the other hand, the decrease in stress at the grain boundary caused by drifting electrons was greater for the solid solution alloy than that for the aging alloy, while the decrease in intragranular stress caused by drifting electrons was significantly smaller for the solid solution alloy than that for the aging alloy. Based on the principles of electron scattering, interaction between electrons, dislocation, and electromigration, the essential reasons for the observed discrepancy in the softening behavior under different strengthening mechanisms were revealed.