Excellent Ductility in the Extruded AZ61 Magnesium Alloy Tube Induced by Electropulsing Treatment during Tension

In this work, we reported the high ductility of an extruded AZ61 magnesium alloy tube achieved by electropulsing current-assisted tension. The elongation of the alloy reached up to about 45%, which is largely superior to the majority of AZ61 wrought Mg alloys. We found that the hardening capacity of the alloy seemed to slightly increase as the electropulsing frequency increased. Furthermore, electropulsing can arouse the serrated flow phenomenon. Here we proposed an equation describing the correlation between the average amplitude and frequency: Aa = C − 6 × 10−3f, where Aa is the average amplitude, f is the frequency, and C is the constant. In addition, introducing electropulsing current pronouncedly reduced the tendency of twinning, but the twinning fraction seemed to fail depending on the electropulsing frequency. Based on microstructure analysis, we concluded that the outstanding ductility of the studied alloy was mainly due to the combined role of the thermal effects from Joule heating, the athermal effects from electron wind, and the magnetic effects from the electropulsing current. The serrated flow phenomenon occurred along stress–strain curves after electropulsing treatment, and the underlying reasons also were uncovered.